xref: /netbsd/external/gpl3/gcc/dist/gcc/d/dmd/dtoh.d (revision f0fbc68b)
1 /**
2  * This module contains the implementation of the C++ header generation available through
3  * the command line switch -Hc.
4  *
5  * Copyright:   Copyright (C) 1999-2022 by The D Language Foundation, All Rights Reserved
6  * Authors:     $(LINK2 https://www.digitalmars.com, Walter Bright)
7  * License:     $(LINK2 https://www.boost.org/LICENSE_1_0.txt, Boost License 1.0)
8  * Source:      $(LINK2 https://github.com/dlang/dmd/blob/master/src/dmd/dtohd, _dtoh.d)
9  * Documentation:  https://dlang.org/phobos/dmd_dtoh.html
10  * Coverage:    https://codecov.io/gh/dlang/dmd/src/master/src/dmd/dtoh.d
11  */
12 module dmd.dtoh;
13 
14 import core.stdc.stdio;
15 import core.stdc.string;
16 import core.stdc.ctype;
17 
18 import dmd.astcodegen;
19 import dmd.astenums;
20 import dmd.arraytypes;
21 import dmd.attrib;
22 import dmd.dsymbol;
23 import dmd.errors;
24 import dmd.globals;
25 import dmd.hdrgen;
26 import dmd.identifier;
27 import dmd.root.filename;
28 import dmd.visitor;
29 import dmd.tokens;
30 
31 import dmd.common.outbuffer;
32 import dmd.utils;
33 
34 //debug = Debug_DtoH;
35 
36 // Generate asserts to validate the header
37 //debug = Debug_DtoH_Checks;
38 
39 /**
40  * Generates a C++ header containing bindings for all `extern(C[++])` declarations
41  * found in the supplied modules.
42  *
43  * Params:
44  *   ms = the modules
45  *
46  * Notes:
47  *  - the header is written to `<global.params.cxxhdrdir>/<global.params.cxxhdrfile>`
48  *    or `stdout` if no explicit file was specified
49  *  - bindings conform to the C++ standard defined in `global.params.cplusplus`
50  *  - ignored declarations are mentioned in a comment if `global.params.doCxxHdrGeneration`
51  *    is set to `CxxHeaderMode.verbose`
52  */
genCppHdrFiles(ref Modules ms)53 extern(C++) void genCppHdrFiles(ref Modules ms)
54 {
55     initialize();
56 
57     OutBuffer fwd;
58     OutBuffer done;
59     OutBuffer decl;
60 
61     // enable indent by spaces on buffers
62     fwd.doindent = true;
63     fwd.spaces = true;
64     decl.doindent = true;
65     decl.spaces = true;
66 
67     scope v = new ToCppBuffer(&fwd, &done, &decl);
68 
69     // Conditionally include another buffer for sanity checks
70     debug (Debug_DtoH_Checks)
71     {
72         OutBuffer check;
73         check.doindent = true;
74         check.spaces = true;
75         v.checkbuf = &check;
76     }
77 
78     OutBuffer buf;
79     buf.doindent = true;
80     buf.spaces = true;
81 
82     foreach (m; ms)
83         m.accept(v);
84 
85     if (global.params.doCxxHdrGeneration == CxxHeaderMode.verbose)
86         buf.printf("// Automatically generated by %s Compiler v%d", global.vendor.ptr, global.versionNumber());
87     else
88         buf.printf("// Automatically generated by %s Compiler", global.vendor.ptr);
89 
90     buf.writenl();
91     buf.writenl();
92     buf.writestringln("#pragma once");
93     buf.writenl();
94     hashInclude(buf, "<assert.h>");
95     hashInclude(buf, "<stddef.h>");
96     hashInclude(buf, "<stdint.h>");
97     hashInclude(buf, "<math.h>");
98 //    buf.writestring(buf, "#include <stdio.h>\n");
99 //    buf.writestring("#include <string.h>\n");
100 
101     // Emit array compatibility because extern(C++) types may have slices
102     // as members (as opposed to function parameters)
103     buf.writestring(`
104 #ifdef CUSTOM_D_ARRAY_TYPE
105 #define _d_dynamicArray CUSTOM_D_ARRAY_TYPE
106 #else
107 /// Represents a D [] array
108 template<typename T>
109 struct _d_dynamicArray final
110 {
111     size_t length;
112     T *ptr;
113 
114     _d_dynamicArray() : length(0), ptr(NULL) { }
115 
116     _d_dynamicArray(size_t length_in, T *ptr_in)
117         : length(length_in), ptr(ptr_in) { }
118 
119     T& operator[](const size_t idx) {
120         assert(idx < length);
121         return ptr[idx];
122     }
123 
124     const T& operator[](const size_t idx) const {
125         assert(idx < length);
126         return ptr[idx];
127     }
128 };
129 #endif
130 `);
131 
132     if (v.hasReal)
133     {
134         hashIf(buf, "!defined(_d_real)");
135         {
136             hashDefine(buf, "_d_real long double");
137         }
138         hashEndIf(buf);
139     }
140     buf.writenl();
141     // buf.writestringln("// fwd:");
142     buf.write(&fwd);
143     if (fwd.length > 0)
144         buf.writenl();
145 
146     // buf.writestringln("// done:");
147     buf.write(&done);
148 
149     // buf.writestringln("// decl:");
150     buf.write(&decl);
151 
152     debug (Debug_DtoH_Checks)
153     {
154         // buf.writestringln("// check:");
155         buf.writestring(`
156 #if OFFSETS
157     template <class T>
158     size_t getSlotNumber(int dummy, ...)
159     {
160         T c;
161         va_list ap;
162         va_start(ap, dummy);
163 
164         void *f = va_arg(ap, void*);
165         for (size_t i = 0; ; i++)
166         {
167             if ( (*(void***)&c)[i] == f)
168             return i;
169         }
170         va_end(ap);
171     }
172 
173     void testOffsets()
174     {
175 `);
176         buf.write(&check);
177         buf.writestring(`
178     }
179 #endif
180 `);
181     }
182 
183     // prevent trailing newlines
184     version (Windows)
185         while (buf.length >= 4 && buf[$-4..$] == "\r\n\r\n")
186             buf.remove(buf.length - 2, 2);
187     else
188         while (buf.length >= 2 && buf[$-2..$] == "\n\n")
189             buf.remove(buf.length - 1, 1);
190 
191 
192     if (global.params.cxxhdrname is null)
193     {
194         // Write to stdout; assume it succeeds
195         size_t n = fwrite(buf[].ptr, 1, buf.length, stdout);
196         assert(n == buf.length); // keep gcc happy about return values
197     }
198     else
199     {
200         const(char)[] name = FileName.combine(global.params.cxxhdrdir, global.params.cxxhdrname);
201         writeFile(Loc.initial, name, buf[]);
202     }
203 }
204 
205 private:
206 
207 /****************************************************
208  * Visitor that writes bindings for `extern(C[++]` declarations.
209  */
210 extern(C++) final class ToCppBuffer : Visitor
211 {
212     alias visit = Visitor.visit;
213 public:
214     enum EnumKind
215     {
216         Int,
217         Numeric,
218         String,
219         Enum,
220         Other
221     }
222 
223     /// Namespace providing the actual AST nodes
224     alias AST = ASTCodegen;
225 
226     /// Visited nodes
227     bool[void*] visited;
228 
229     /// Forward declared nodes (which might not be emitted yet)
230     bool[void*] forwarded;
231 
232     /// Buffer for forward declarations
233     OutBuffer* fwdbuf;
234 
235     /// Buffer for integrity checks
236     debug (Debug_DtoH_Checks) OutBuffer* checkbuf;
237 
238     /// Buffer for declarations that must emitted before the currently
239     /// visited node but can't be forward declared (see `includeSymbol`)
240     OutBuffer* donebuf;
241 
242     /// Default buffer for the currently visited declaration
243     OutBuffer* buf;
244 
245     /// The generated header uses `real` emitted as `_d_real`?
246     bool hasReal;
247 
248     /// The generated header should contain comments for skipped declarations?
249     const bool printIgnored;
250 
251     /// State specific to the current context which depends
252     /// on the currently visited node and it's parents
253     static struct Context
254     {
255         /// Default linkage in the current scope (e.g. LINK.c inside `extern(C) { ... }`)
256         LINK linkage = LINK.d;
257 
258         /// Enclosing class / struct / union
259         AST.AggregateDeclaration adparent;
260 
261         /// Enclosing template declaration
262         AST.TemplateDeclaration tdparent;
263 
264         /// Identifier of the currently visited `VarDeclaration`
265         /// (required to write variables of funtion pointers)
266         Identifier ident;
267 
268         /// Original type of the currently visited declaration
269         AST.Type origType;
270 
271         /// Last written visibility level applying to the current scope
272         AST.Visibility.Kind currentVisibility;
273 
274         /// Currently applicable storage classes
275         AST.STC storageClass;
276 
277          /// How many symbols were ignored
278         int ignoredCounter;
279 
280         /// Currently visited types are required by another declaration
281         /// and hence must be emitted
282         bool mustEmit;
283 
284         /// Processing a type that can be forward referenced
285         bool forwarding;
286 
287         /// Inside of an anonymous struct/union (AnonDeclaration)
288         bool inAnonymousDecl;
289     }
290 
291     /// Informations about the current context in the AST
292     Context context;
293     alias context this;
294 
295     this(OutBuffer* fwdbuf, OutBuffer* donebuf, OutBuffer* buf)
296     {
297         this.fwdbuf = fwdbuf;
298         this.donebuf = donebuf;
299         this.buf = buf;
300         this.printIgnored = global.params.doCxxHdrGeneration == CxxHeaderMode.verbose;
301     }
302 
303     /**
304      * Emits `dsym` into `donebuf` s.t. it is declared before the currently
305      * visited symbol that written to `buf`.
306      *
307      * Temporarily clears `context` to behave as if it was visited normally.
308      */
309     private void includeSymbol(AST.Dsymbol dsym)
310     {
311         debug (Debug_DtoH)
312         {
313             printf("[includeSymbol(AST.Dsymbol) enter] %s\n", dsym.toChars());
314             scope(exit) printf("[includeSymbol(AST.Dsymbol) exit] %s\n", dsym.toChars());
315         }
316 
317         auto ptr = cast(void*) dsym in visited;
318         if (ptr && *ptr)
319             return;
320 
321         // Temporary replacement for `buf` which is appended to `donebuf`
322         OutBuffer decl;
323         decl.doindent = true;
324         decl.spaces = true;
325         scope (exit) donebuf.write(&decl);
326 
327         auto ctxStash = this.context;
328         auto bufStash = this.buf;
329 
330         this.context = Context.init;
331         this.buf = &decl;
332         this.mustEmit = true;
333 
334         dsym.accept(this);
335 
336         this.context = ctxStash;
337         this.buf = bufStash;
338     }
339 
340     /// Determines what kind of enum `type` is (see `EnumKind`)
341     private EnumKind getEnumKind(AST.Type type)
342     {
343         if (type) switch (type.ty)
344         {
345             case AST.Tint32:
346                 return EnumKind.Int;
347             case AST.Tbool,
348                 AST.Tchar, AST.Twchar, AST.Tdchar,
349                 AST.Tint8, AST.Tuns8,
350                 AST.Tint16, AST.Tuns16,
351                 AST.Tuns32,
352                 AST.Tint64, AST.Tuns64:
353                 return EnumKind.Numeric;
354             case AST.Tarray:
355                 if (type.isString())
356                     return EnumKind.String;
357                 break;
358             case AST.Tenum:
359                 return EnumKind.Enum;
360             default:
361                 break;
362         }
363         return EnumKind.Other;
364     }
365 
366     /// Determines the type used to represent `type` in C++.
367     /// Returns: `const [w,d]char*` for `[w,d]string` or `type`
368     private AST.Type determineEnumType(AST.Type type)
369     {
370         if (auto arr = type.isTypeDArray())
371         {
372             switch (arr.next.ty)
373             {
374                 case AST.Tchar:  return AST.Type.tchar.constOf.pointerTo;
375                 case AST.Twchar: return AST.Type.twchar.constOf.pointerTo;
376                 case AST.Tdchar: return AST.Type.tdchar.constOf.pointerTo;
377                 default: break;
378             }
379         }
380         return type;
381     }
382 
383     /// Writes a final `;` and insert an empty line outside of aggregates
384     private void writeDeclEnd()
385     {
386         buf.writestringln(";");
387 
388         if (!adparent)
389             buf.writenl();
390     }
391 
392     /// Writes the corresponding access specifier if necessary
393     private void writeProtection(const AST.Visibility.Kind kind)
394     {
395         // Don't write visibility for global declarations
396         if (!adparent || inAnonymousDecl)
397             return;
398 
399         string token;
400 
401         switch(kind) with(AST.Visibility.Kind)
402         {
403             case none, private_:
404                 if (this.currentVisibility == AST.Visibility.Kind.private_)
405                     return;
406                 this.currentVisibility = AST.Visibility.Kind.private_;
407                 token = "private:";
408                 break;
409 
410             case package_, protected_:
411                 if (this.currentVisibility == AST.Visibility.Kind.protected_)
412                     return;
413                 this.currentVisibility = AST.Visibility.Kind.protected_;
414                 token = "protected:";
415                 break;
416 
417             case undefined, public_, export_:
418                 if (this.currentVisibility == AST.Visibility.Kind.public_)
419                     return;
420                 this.currentVisibility = AST.Visibility.Kind.public_;
421                 token = "public:";
422                 break;
423 
424             default:
425                 printf("Unexpected visibility: %d!\n", kind);
426                 assert(0);
427         }
428 
429         buf.level--;
430         buf.writestringln(token);
431         buf.level++;
432     }
433 
434     /**
435      * Writes an identifier into `buf` and checks for reserved identifiers. The
436      * parameter `canFix` determines how this function handles C++ keywords:
437      *
438      * `false` => Raise a warning and print the identifier as-is
439      * `true`  => Append an underscore to the identifier
440      *
441      * Params:
442      *   s        = the symbol denoting the identifier
443      *   canFixup = whether the identifier may be changed without affecting
444      *              binary compatibility
445      */
446     private void writeIdentifier(const AST.Dsymbol s, const bool canFix = false)
447     {
448         if (const mn = getMangleOverride(s))
449             return buf.writestring(mn);
450 
451         writeIdentifier(s.ident, s.loc, s.kind(), canFix);
452     }
453 
454     /** Overload of `writeIdentifier` used for all AST nodes not descending from Dsymbol **/
455     private void writeIdentifier(const Identifier ident, const Loc loc, const char* kind, const bool canFix = false)
456     {
457         bool needsFix;
458 
459         void warnCxxCompat(const(char)* reason)
460         {
461             if (canFix)
462             {
463                 needsFix = true;
464                 return;
465             }
466 
467             __gshared bool warned = false;
468             warning(loc, "%s `%s` is a %s", kind, ident.toChars(), reason);
469 
470             if (!warned)
471             {
472                 warningSupplemental(loc, "The generated C++ header will contain " ~
473                                     "identifiers that are keywords in C++");
474                 warned = true;
475             }
476         }
477 
478         if (global.params.warnings != DiagnosticReporting.off || canFix)
479         {
480             // Warn about identifiers that are keywords in C++.
481             if (auto kc = keywordClass(ident))
482                 warnCxxCompat(kc);
483         }
484         buf.writestring(ident.toString());
485         if (needsFix)
486             buf.writeByte('_');
487     }
488 
489     /// Checks whether `t` is a type that can be exported to C++
490     private bool isSupportedType(AST.Type t)
491     {
492         if (!t)
493         {
494             assert(tdparent);
495             return true;
496         }
497 
498         switch (t.ty)
499         {
500             // Nested types
501             case AST.Tarray:
502             case AST.Tsarray:
503             case AST.Tpointer:
504             case AST.Treference:
505             case AST.Tdelegate:
506                 return isSupportedType((cast(AST.TypeNext) t).next);
507 
508             // Function pointers
509             case AST.Tfunction:
510             {
511                 auto tf = cast(AST.TypeFunction) t;
512                 if (!isSupportedType(tf.next))
513                     return false;
514                 foreach (_, param; tf.parameterList)
515                 {
516                     if (!isSupportedType(param.type))
517                         return false;
518                 }
519                 return true;
520             }
521 
522             // Noreturn has a different mangling
523             case AST.Tnoreturn:
524 
525             // _Imaginary is C only.
526             case AST.Timaginary32:
527             case AST.Timaginary64:
528             case AST.Timaginary80:
529                 return false;
530             default:
531                 return true;
532         }
533     }
534 
535     override void visit(AST.Dsymbol s)
536     {
537         debug (Debug_DtoH)
538         {
539             mixin(traceVisit!s);
540             import dmd.asttypename;
541             printf("[AST.Dsymbol enter] %s\n", s.astTypeName().ptr);
542         }
543     }
544 
545     override void visit(AST.Import i)
546     {
547         debug (Debug_DtoH) mixin(traceVisit!i);
548 
549         /// Writes `using <alias_> = <sym.ident>` into `buf`
550         const(char*) writeImport(AST.Dsymbol sym, const Identifier alias_)
551         {
552             /// `using` was introduced in C++ 11 and only works for types...
553             if (global.params.cplusplus < CppStdRevision.cpp11)
554                 return "requires C++11";
555 
556             if (auto ad = sym.isAliasDeclaration())
557             {
558                 sym = ad.toAlias();
559                 ad = sym.isAliasDeclaration();
560 
561                 // Might be an alias to a basic type
562                 if (ad && !ad.aliassym && ad.type)
563                     goto Emit;
564             }
565 
566             // Restricted to types and other aliases
567             if (!sym.isScopeDsymbol() && !sym.isAggregateDeclaration())
568                 return "only supports types";
569 
570             // Write `using <alias_> = `<sym>`
571             Emit:
572             buf.writestring("using ");
573             writeIdentifier(alias_, i.loc, "renamed import");
574             buf.writestring(" = ");
575             // Start at module scope to avoid collisions with local symbols
576             if (this.context.adparent)
577                 buf.writestring("::");
578             buf.writestring(sym.ident.toString());
579             writeDeclEnd();
580             return null;
581         }
582 
583         // Only missing without semantic analysis
584         // FIXME: Templates need work due to missing parent & imported module
585         if (!i.parent)
586         {
587             assert(tdparent);
588             ignored("`%s` because it's inside of a template declaration", i.toChars());
589             return;
590         }
591 
592         // Non-public imports don't create new symbols, include as needed
593         if (i.visibility.kind < AST.Visibility.Kind.public_)
594             return;
595 
596         // Symbols from static imports should be emitted inline
597         if (i.isstatic)
598             return;
599 
600         const isLocal = !i.parent.isModule();
601 
602         // Need module for symbol lookup
603         assert(i.mod);
604 
605         // Emit an alias for each public module member
606         if (isLocal && i.names.length == 0)
607         {
608             assert(i.mod.symtab);
609 
610             // Sort alphabetically s.t. slight changes in semantic don't cause
611             // massive changes in the order of declarations
612             AST.Dsymbols entries;
613             entries.reserve(i.mod.symtab.length);
614 
615             foreach (entry; i.mod.symtab.tab.asRange)
616             {
617                 // Skip anonymous / invisible members
618                 import dmd.access : symbolIsVisible;
619                 if (!entry.key.isAnonymous() && symbolIsVisible(i, entry.value))
620                     entries.push(entry.value);
621             }
622 
623             // Seperate function because of a spurious dual-context deprecation
624             static int compare(const AST.Dsymbol* a, const AST.Dsymbol* b)
625             {
626                 return strcmp(a.ident.toChars(), b.ident.toChars());
627             }
628             entries.sort!compare();
629 
630             foreach (sym; entries)
631             {
632                 includeSymbol(sym);
633                 if (auto err = writeImport(sym, sym.ident))
634                     ignored("public import for `%s` because `using` %s", sym.ident.toChars(), err);
635             }
636             return;
637         }
638 
639         // Include all public imports and emit using declarations for each alias
640         foreach (const idx, name; i.names)
641         {
642             // Search the imported symbol
643             auto sym = i.mod.search(Loc.initial, name);
644             assert(sym); // Missing imports should error during semantic
645 
646             includeSymbol(sym);
647 
648             // Detect the assigned name for renamed import
649             auto alias_ = i.aliases[idx];
650             if (!alias_)
651                 continue;
652 
653             if (auto err = writeImport(sym, alias_))
654                 ignored("renamed import `%s = %s` because `using` %s", alias_.toChars(), name.toChars(), err);
655         }
656     }
657 
658     override void visit(AST.AttribDeclaration pd)
659     {
660         debug (Debug_DtoH) mixin(traceVisit!pd);
661 
662         Dsymbols* decl = pd.include(null);
663         if (!decl)
664             return;
665 
666         foreach (s; *decl)
667         {
668             if (adparent || s.visible().kind >= AST.Visibility.Kind.public_)
669                 s.accept(this);
670         }
671     }
672 
673     override void visit(AST.StorageClassDeclaration scd)
674     {
675         debug (Debug_DtoH) mixin(traceVisit!scd);
676 
677         const stcStash = this.storageClass;
678         this.storageClass |= scd.stc;
679         visit(cast(AST.AttribDeclaration) scd);
680         this.storageClass = stcStash;
681     }
682 
683     override void visit(AST.LinkDeclaration ld)
684     {
685         debug (Debug_DtoH) mixin(traceVisit!ld);
686 
687         auto save = linkage;
688         linkage = ld.linkage;
689         visit(cast(AST.AttribDeclaration)ld);
690         linkage = save;
691     }
692 
693     override void visit(AST.CPPMangleDeclaration md)
694     {
695         debug (Debug_DtoH) mixin(traceVisit!md);
696 
697         const oldLinkage = this.linkage;
698         this.linkage = LINK.cpp;
699         visit(cast(AST.AttribDeclaration) md);
700         this.linkage = oldLinkage;
701     }
702 
703     override void visit(AST.Module m)
704     {
705         debug (Debug_DtoH) mixin(traceVisit!m);
706 
707         foreach (s; *m.members)
708         {
709             if (s.visible().kind < AST.Visibility.Kind.public_)
710                 continue;
711             s.accept(this);
712         }
713     }
714 
715     override void visit(AST.FuncDeclaration fd)
716     {
717         debug (Debug_DtoH) mixin(traceVisit!fd);
718 
719         if (cast(void*)fd in visited)
720             return;
721         // printf("FuncDeclaration %s %s\n", fd.toPrettyChars(), fd.type.toChars());
722         visited[cast(void*)fd] = true;
723 
724         // silently ignore non-user-defined destructors
725         if (fd.isGenerated && fd.isDtorDeclaration())
726             return;
727 
728         // Note that tf might be null for templated (member) functions
729         auto tf = cast(AST.TypeFunction)fd.type;
730         if ((tf && (tf.linkage != LINK.c || adparent) && tf.linkage != LINK.cpp) || (!tf && fd.isPostBlitDeclaration()))
731         {
732             ignored("function %s because of linkage", fd.toPrettyChars());
733             return checkFunctionNeedsPlaceholder(fd);
734         }
735         if (fd.mangleOverride && tf && tf.linkage != LINK.c)
736         {
737             ignored("function %s because C++ doesn't support explicit mangling", fd.toPrettyChars());
738             return checkFunctionNeedsPlaceholder(fd);
739         }
740         if (!adparent && !fd.fbody)
741         {
742             ignored("function %s because it is extern", fd.toPrettyChars());
743             return;
744         }
745         if (fd.visibility.kind == AST.Visibility.Kind.none || fd.visibility.kind == AST.Visibility.Kind.private_)
746         {
747             ignored("function %s because it is private", fd.toPrettyChars());
748             return;
749         }
750         if (tf && !isSupportedType(tf.next))
751         {
752             ignored("function %s because its return type cannot be mapped to C++", fd.toPrettyChars());
753             return checkFunctionNeedsPlaceholder(fd);
754         }
755         if (tf) foreach (i, fparam; tf.parameterList)
756         {
757             if (!isSupportedType(fparam.type))
758             {
759                 ignored("function %s because one of its parameters has type `%s` which cannot be mapped to C++",
760                         fd.toPrettyChars(), fparam.type.toChars());
761                 return checkFunctionNeedsPlaceholder(fd);
762             }
763         }
764 
765         writeProtection(fd.visibility.kind);
766 
767         if (tf && tf.linkage == LINK.c)
768             buf.writestring("extern \"C\" ");
769         else if (!adparent)
770             buf.writestring("extern ");
771         if (adparent && fd.isStatic())
772             buf.writestring("static ");
773         else if (adparent && (
774             // Virtual functions in non-templated classes
775             (fd.vtblIndex != -1 && !fd.isOverride()) ||
776 
777             // Virtual functions in templated classes (fd.vtblIndex still -1)
778             (tdparent && adparent.isClassDeclaration() && !(this.storageClass & AST.STC.final_ || fd.isFinal))))
779                 buf.writestring("virtual ");
780 
781         debug (Debug_DtoH_Checks)
782         if (adparent && !tdparent)
783         {
784             auto s = adparent.search(Loc.initial, fd.ident);
785             auto cd = adparent.isClassDeclaration();
786 
787             if (!(adparent.storage_class & AST.STC.abstract_) &&
788                 !(cd && cd.isAbstract()) &&
789                 s is fd && !fd.overnext)
790             {
791                 const cn = adparent.ident.toChars();
792                 const fn = fd.ident.toChars();
793                 const vi = fd.vtblIndex;
794 
795                 checkbuf.printf("assert(getSlotNumber <%s>(0, &%s::%s) == %d);",
796                                                        cn,     cn, fn,    vi);
797                 checkbuf.writenl();
798            }
799         }
800 
801         if (adparent && fd.isDisabled && global.params.cplusplus < CppStdRevision.cpp11)
802             writeProtection(AST.Visibility.Kind.private_);
803         funcToBuffer(tf, fd);
804         // FIXME: How to determine if fd is const without tf?
805         if (adparent && tf && (tf.isConst() || tf.isImmutable()))
806         {
807             bool fdOverridesAreConst = true;
808             foreach (fdv; fd.foverrides)
809             {
810                 auto tfv = cast(AST.TypeFunction)fdv.type;
811                 if (!tfv.isConst() && !tfv.isImmutable())
812                 {
813                     fdOverridesAreConst = false;
814                     break;
815                 }
816             }
817 
818             buf.writestring(fdOverridesAreConst ? " const" : " /* const */");
819         }
820         if (adparent && fd.isAbstract())
821             buf.writestring(" = 0");
822         if (adparent && fd.isDisabled && global.params.cplusplus >= CppStdRevision.cpp11)
823             buf.writestring(" = delete");
824         buf.writestringln(";");
825         if (adparent && fd.isDisabled && global.params.cplusplus < CppStdRevision.cpp11)
826             writeProtection(AST.Visibility.Kind.public_);
827 
828         if (!adparent)
829             buf.writenl();
830 
831     }
832 
833     /++
834      + Checks whether `fd` is a function that requires a dummy declaration
835      + instead of simply emitting the declaration (because it would cause
836      + ABI / behaviour issues). This includes:
837      +
838      + - virtual functions to ensure proper vtable layout
839      + - destructors that would break RAII
840      +/
841     private void checkFunctionNeedsPlaceholder(AST.FuncDeclaration fd)
842     {
843         // Omit redundant declarations - the slot was already
844         // reserved in the base class
845         if (fd.isVirtual() && fd.isIntroducing())
846         {
847             // Hide placeholders because they are not ABI compatible
848             writeProtection(AST.Visibility.Kind.private_);
849 
850             __gshared int counter; // Ensure unique names in all cases
851             buf.printf("virtual void __vtable_slot_%u();", counter++);
852             buf.writenl();
853         }
854         else if (fd.isDtorDeclaration())
855         {
856             // Create inaccessible dtor to prevent code from keeping instances that
857             // need to be destroyed on the C++ side (but cannot call the dtor)
858             writeProtection(AST.Visibility.Kind.private_);
859             buf.writeByte('~');
860             buf.writestring(adparent.ident.toString());
861             buf.writestringln("();");
862         }
863     }
864 
865     override void visit(AST.UnitTestDeclaration utd)
866     {
867         debug (Debug_DtoH) mixin(traceVisit!utd);
868     }
869 
870     override void visit(AST.VarDeclaration vd)
871     {
872         debug (Debug_DtoH) mixin(traceVisit!vd);
873 
874         if (!shouldEmitAndMarkVisited(vd))
875             return;
876 
877         // Tuple field are expanded into multiple VarDeclarations
878         // (we'll visit them later)
879         if (vd.type && vd.type.isTypeTuple())
880             return;
881 
882         if (vd.originalType && vd.type == AST.Type.tsize_t)
883             origType = vd.originalType;
884         scope(exit) origType = null;
885 
886         if (!vd.alignment.isDefault() && !vd.alignment.isUnknown())
887         {
888             buf.printf("// Ignoring var %s alignment %d", vd.toChars(), vd.alignment.get());
889             buf.writenl();
890         }
891 
892         // Determine the variable type which might be missing inside of
893         // template declarations. Infer the type from the initializer then
894         AST.Type type = vd.type;
895         if (!type)
896         {
897             assert(tdparent);
898 
899             // Just a precaution, implicit type without initializer should be rejected
900             if (!vd._init)
901                 return;
902 
903             if (auto ei = vd._init.isExpInitializer())
904                 type = ei.exp.type;
905 
906             // Can happen if the expression needs further semantic
907             if (!type)
908             {
909                 ignored("%s because the type could not be determined", vd.toPrettyChars());
910                 return;
911             }
912 
913             // Apply const/immutable to the inferred type
914             if (vd.storage_class & (AST.STC.const_ | AST.STC.immutable_))
915                 type = type.constOf();
916         }
917 
918         if (vd.storage_class & AST.STC.manifest)
919         {
920             EnumKind kind = getEnumKind(type);
921 
922             if (vd.visibility.kind == AST.Visibility.Kind.none || vd.visibility.kind == AST.Visibility.Kind.private_) {
923                 ignored("enum `%s` because it is `%s`.", vd.toPrettyChars(), AST.visibilityToChars(vd.visibility.kind));
924                 return;
925             }
926 
927             writeProtection(vd.visibility.kind);
928 
929             final switch (kind)
930             {
931                 case EnumKind.Int, EnumKind.Numeric:
932                     // 'enum : type' is only available from C++-11 onwards.
933                     if (global.params.cplusplus < CppStdRevision.cpp11)
934                         goto case;
935                     buf.writestring("enum : ");
936                     determineEnumType(type).accept(this);
937                     buf.writestring(" { ");
938                     writeIdentifier(vd, true);
939                     buf.writestring(" = ");
940                     auto ie = AST.initializerToExpression(vd._init).isIntegerExp();
941                     visitInteger(ie.toInteger(), type);
942                     buf.writestring(" };");
943                     break;
944 
945                 case EnumKind.String, EnumKind.Enum:
946                     buf.writestring("static ");
947                     auto target = determineEnumType(type);
948                     target.accept(this);
949                     buf.writestring(" const ");
950                     writeIdentifier(vd, true);
951                     buf.writestring(" = ");
952                     auto e = AST.initializerToExpression(vd._init);
953                     printExpressionFor(target, e);
954                     buf.writestring(";");
955                     break;
956 
957                 case EnumKind.Other:
958                     ignored("enum `%s` because type `%s` is currently not supported for enum constants.", vd.toPrettyChars(), type.toChars());
959                     return;
960             }
961             buf.writenl();
962             buf.writenl();
963             return;
964         }
965 
966         if (vd.storage_class & (AST.STC.static_ | AST.STC.extern_ | AST.STC.gshared) ||
967         vd.parent && vd.parent.isModule())
968         {
969             const vdLinkage = vd.resolvedLinkage();
970             if (vdLinkage != LINK.c && vdLinkage != LINK.cpp && !(tdparent && (this.linkage == LINK.c || this.linkage == LINK.cpp)))
971             {
972                 ignored("variable %s because of linkage", vd.toPrettyChars());
973                 return;
974             }
975             if (vd.mangleOverride && vdLinkage != LINK.c)
976             {
977                 ignored("variable %s because C++ doesn't support explicit mangling", vd.toPrettyChars());
978                 return;
979             }
980             if (!isSupportedType(type))
981             {
982                 ignored("variable %s because its type cannot be mapped to C++", vd.toPrettyChars());
983                 return;
984             }
985             if (auto kc = keywordClass(vd.ident))
986             {
987                 ignored("variable %s because its name is a %s", vd.toPrettyChars(), kc);
988                 return;
989             }
990             writeProtection(vd.visibility.kind);
991             if (vdLinkage == LINK.c)
992                 buf.writestring("extern \"C\" ");
993             else if (!adparent)
994                 buf.writestring("extern ");
995             if (adparent)
996                 buf.writestring("static ");
997             typeToBuffer(type, vd);
998             writeDeclEnd();
999             return;
1000         }
1001 
1002         if (adparent)
1003         {
1004             writeProtection(vd.visibility.kind);
1005             typeToBuffer(type, vd, true);
1006             buf.writestringln(";");
1007 
1008             debug (Debug_DtoH_Checks)
1009             {
1010                 checkbuf.level++;
1011                 const pn = adparent.ident.toChars();
1012                 const vn = vd.ident.toChars();
1013                 const vo = vd.offset;
1014                 checkbuf.printf("assert(offsetof(%s, %s) == %d);",
1015                                                 pn, vn,    vo);
1016                 checkbuf.writenl();
1017                 checkbuf.level--;
1018             }
1019             return;
1020         }
1021 
1022         visit(cast(AST.Dsymbol)vd);
1023     }
1024 
1025     override void visit(AST.TypeInfoDeclaration tid)
1026     {
1027         debug (Debug_DtoH) mixin(traceVisit!tid);
1028     }
1029 
1030     override void visit(AST.AliasDeclaration ad)
1031     {
1032         debug (Debug_DtoH) mixin(traceVisit!ad);
1033 
1034         if (!shouldEmitAndMarkVisited(ad))
1035             return;
1036 
1037         writeProtection(ad.visibility.kind);
1038 
1039         if (auto t = ad.type)
1040         {
1041             if (t.ty == AST.Tdelegate || t.ty == AST.Tident)
1042             {
1043                 visit(cast(AST.Dsymbol)ad);
1044                 return;
1045             }
1046 
1047             // for function pointers we need to original type
1048             if (ad.originalType && ad.type.ty == AST.Tpointer &&
1049                 (cast(AST.TypePointer)t).nextOf.ty == AST.Tfunction)
1050             {
1051                 origType = ad.originalType;
1052             }
1053             scope(exit) origType = null;
1054 
1055             buf.writestring("typedef ");
1056             typeToBuffer(origType !is null ? origType : t, ad);
1057             writeDeclEnd();
1058             return;
1059         }
1060         if (!ad.aliassym)
1061         {
1062             assert(0);
1063         }
1064         if (auto ti = ad.aliassym.isTemplateInstance())
1065         {
1066             visitTi(ti);
1067             return;
1068         }
1069         if (auto sd = ad.aliassym.isStructDeclaration())
1070         {
1071             buf.writestring("typedef ");
1072             sd.type.accept(this);
1073             buf.writestring(" ");
1074             writeIdentifier(ad);
1075             writeDeclEnd();
1076             return;
1077         }
1078         else if (auto td = ad.aliassym.isTemplateDeclaration())
1079         {
1080             if (global.params.cplusplus < CppStdRevision.cpp11)
1081             {
1082                 ignored("%s because `using` declarations require C++ 11", ad.toPrettyChars());
1083                 return;
1084             }
1085 
1086             printTemplateParams(td);
1087             buf.writestring("using ");
1088             writeIdentifier(ad);
1089             buf.writestring(" = ");
1090             writeFullName(td);
1091             buf.writeByte('<');
1092 
1093             foreach (const idx, const p; *td.parameters)
1094             {
1095                 if (idx)
1096                     buf.writestring(", ");
1097                 writeIdentifier(p.ident, p.loc, "parameter", true);
1098             }
1099             buf.writestringln(">;");
1100             return;
1101         }
1102 
1103         auto fd = ad.aliassym.isFuncDeclaration();
1104 
1105         if (fd && (fd.isGenerated() || fd.isDtorDeclaration()))
1106         {
1107             // Ignore. It's taken care of while visiting FuncDeclaration
1108             return;
1109         }
1110 
1111         // Recognize member function aliases, e.g. alias visit = Parent.visit;
1112         if (adparent && fd)
1113         {
1114             auto pd = fd.isMember();
1115             if (!pd)
1116             {
1117                 ignored("%s because free functions cannot be aliased in C++", ad.toPrettyChars());
1118             }
1119             else if (global.params.cplusplus < CppStdRevision.cpp11)
1120             {
1121                 ignored("%s because `using` declarations require C++ 11", ad.toPrettyChars());
1122             }
1123             else if (ad.ident != fd.ident)
1124             {
1125                 ignored("%s because `using` cannot rename functions in aggregates", ad.toPrettyChars());
1126             }
1127             else if (fd.toAliasFunc().parent.isTemplateMixin())
1128             {
1129                 // Member's of template mixins are directly emitted into the aggregate
1130             }
1131             else
1132             {
1133                 buf.writestring("using ");
1134 
1135                 // Print prefix of the base class if this function originates from a superclass
1136                 // because alias might be resolved through multiple classes, e.g.
1137                 // e.g. for alias visit = typeof(super).visit in the visitors
1138                 if (!fd.isIntroducing())
1139                     printPrefix(ad.toParent().isClassDeclaration().baseClass);
1140                 else
1141                     printPrefix(pd);
1142 
1143                 buf.writestring(fd.ident.toChars());
1144                 buf.writestringln(";");
1145             }
1146             return;
1147         }
1148 
1149         ignored("%s %s", ad.aliassym.kind(), ad.aliassym.toPrettyChars());
1150     }
1151 
1152     override void visit(AST.Nspace ns)
1153     {
1154         debug (Debug_DtoH) mixin(traceVisit!ns);
1155         handleNspace(ns, ns.members);
1156     }
1157 
1158     override void visit(AST.CPPNamespaceDeclaration ns)
1159     {
1160         debug (Debug_DtoH) mixin(traceVisit!ns);
1161         handleNspace(ns, ns.decl);
1162     }
1163 
1164     /// Writes the namespace declaration and visits all members
1165     private void handleNspace(AST.Dsymbol namespace, Dsymbols* members)
1166     {
1167         buf.writestring("namespace ");
1168         writeIdentifier(namespace);
1169         buf.writenl();
1170         buf.writestring("{");
1171         buf.writenl();
1172         buf.level++;
1173         foreach(decl;(*members))
1174         {
1175             decl.accept(this);
1176         }
1177         buf.level--;
1178         buf.writestring("}");
1179         buf.writenl();
1180     }
1181 
1182     override void visit(AST.AnonDeclaration ad)
1183     {
1184         debug (Debug_DtoH) mixin(traceVisit!ad);
1185 
1186         const anonStash = inAnonymousDecl;
1187         inAnonymousDecl = true;
1188         scope (exit) inAnonymousDecl = anonStash;
1189 
1190         buf.writestringln(ad.isunion ? "union" : "struct");
1191         buf.writestringln("{");
1192         buf.level++;
1193         foreach (s; *ad.decl)
1194         {
1195             s.accept(this);
1196         }
1197         buf.level--;
1198         buf.writestringln("};");
1199     }
1200 
1201     private bool memberField(AST.VarDeclaration vd)
1202     {
1203         if (!vd.type || !vd.type.deco || !vd.ident)
1204             return false;
1205         if (!vd.isField())
1206             return false;
1207         if (vd.type.ty == AST.Tfunction)
1208             return false;
1209         if (vd.type.ty == AST.Tsarray)
1210             return false;
1211         return true;
1212     }
1213 
1214     override void visit(AST.StructDeclaration sd)
1215     {
1216         debug (Debug_DtoH) mixin(traceVisit!sd);
1217 
1218         if (!shouldEmitAndMarkVisited(sd))
1219             return;
1220 
1221         const ignoredStash = this.ignoredCounter;
1222         scope (exit) this.ignoredCounter = ignoredStash;
1223 
1224         pushAlignToBuffer(sd.alignment);
1225 
1226         writeProtection(sd.visibility.kind);
1227 
1228         const structAsClass = sd.cppmangle == CPPMANGLE.asClass;
1229         if (sd.isUnionDeclaration())
1230             buf.writestring("union ");
1231         else
1232             buf.writestring(structAsClass ? "class " : "struct ");
1233 
1234         writeIdentifier(sd);
1235         if (!sd.members)
1236         {
1237             buf.writestringln(";");
1238             buf.writenl();
1239             return;
1240         }
1241 
1242         // D structs are always final
1243         if (!sd.isUnionDeclaration())
1244             buf.writestring(" final");
1245 
1246         buf.writenl();
1247         buf.writestring("{");
1248 
1249         const protStash = this.currentVisibility;
1250         this.currentVisibility = structAsClass ? AST.Visibility.Kind.private_ : AST.Visibility.Kind.public_;
1251         scope (exit) this.currentVisibility = protStash;
1252 
1253         buf.level++;
1254         buf.writenl();
1255         auto save = adparent;
1256         adparent = sd;
1257 
1258         foreach (m; *sd.members)
1259         {
1260             m.accept(this);
1261         }
1262         // Generate default ctor
1263         if (!sd.noDefaultCtor && !sd.isUnionDeclaration())
1264         {
1265             writeProtection(AST.Visibility.Kind.public_);
1266             buf.printf("%s()", sd.ident.toChars());
1267             size_t varCount;
1268             bool first = true;
1269             buf.level++;
1270             foreach (m; *sd.members)
1271             {
1272                 if (auto vd = m.isVarDeclaration())
1273                 {
1274                     if (!memberField(vd))
1275                         continue;
1276                     varCount++;
1277 
1278                     if (!vd._init && !vd.type.isTypeBasic() && !vd.type.isTypePointer && !vd.type.isTypeStruct &&
1279                         !vd.type.isTypeClass && !vd.type.isTypeDArray && !vd.type.isTypeSArray)
1280                     {
1281                         continue;
1282                     }
1283                     if (vd._init && vd._init.isVoidInitializer())
1284                         continue;
1285 
1286                     if (first)
1287                     {
1288                         buf.writestringln(" :");
1289                         first = false;
1290                     }
1291                     else
1292                     {
1293                         buf.writestringln(",");
1294                     }
1295                     writeIdentifier(vd, true);
1296                     buf.writeByte('(');
1297 
1298                     if (vd._init)
1299                     {
1300                         auto e = AST.initializerToExpression(vd._init);
1301                         printExpressionFor(vd.type, e, true);
1302                     }
1303                     buf.printf(")");
1304                 }
1305             }
1306             buf.level--;
1307             buf.writenl();
1308             buf.writestringln("{");
1309             buf.writestringln("}");
1310             auto ctor = sd.ctor ? sd.ctor.isFuncDeclaration() : null;
1311             if (varCount && (!ctor || ctor.storage_class & AST.STC.disable))
1312             {
1313                 buf.printf("%s(", sd.ident.toChars());
1314                 first = true;
1315                 foreach (m; *sd.members)
1316                 {
1317                     if (auto vd = m.isVarDeclaration())
1318                     {
1319                         if (!memberField(vd))
1320                             continue;
1321                         if (!first)
1322                             buf.writestring(", ");
1323                         assert(vd.type);
1324                         assert(vd.ident);
1325                         typeToBuffer(vd.type, vd, true);
1326                         // Don't print default value for first parameter to not clash
1327                         // with the default ctor defined above
1328                         if (!first)
1329                         {
1330                             buf.writestring(" = ");
1331                             printExpressionFor(vd.type, findDefaultInitializer(vd));
1332                         }
1333                         first = false;
1334                     }
1335                 }
1336                 buf.writestring(") :");
1337                 buf.level++;
1338                 buf.writenl();
1339 
1340                 first = true;
1341                 foreach (m; *sd.members)
1342                 {
1343                     if (auto vd = m.isVarDeclaration())
1344                     {
1345                         if (!memberField(vd))
1346                             continue;
1347 
1348                         if (first)
1349                             first = false;
1350                         else
1351                             buf.writestringln(",");
1352 
1353                         writeIdentifier(vd, true);
1354                         buf.writeByte('(');
1355                         writeIdentifier(vd, true);
1356                         buf.writeByte(')');
1357                     }
1358                 }
1359                 buf.writenl();
1360                 buf.writestringln("{}");
1361                 buf.level--;
1362             }
1363         }
1364 
1365         buf.level--;
1366         adparent = save;
1367         buf.writestringln("};");
1368 
1369         popAlignToBuffer(sd.alignment);
1370         buf.writenl();
1371 
1372         // Workaround because size triggers a forward-reference error
1373         // for struct templates (the size is undetermined even if the
1374         // size doesn't depend on the parameters)
1375         debug (Debug_DtoH_Checks)
1376         if (!tdparent)
1377         {
1378             checkbuf.level++;
1379             const sn = sd.ident.toChars();
1380             const sz = sd.size(Loc.initial);
1381             checkbuf.printf("assert(sizeof(%s) == %llu);", sn, sz);
1382             checkbuf.writenl();
1383             checkbuf.level--;
1384         }
1385     }
1386 
1387     /// Starts a custom alignment section using `#pragma pack` if
1388     /// `alignment` specifies a custom alignment
1389     private void pushAlignToBuffer(structalign_t alignment)
1390     {
1391         // DMD ensures alignment is a power of two
1392         //assert(alignment > 0 && ((alignment & (alignment - 1)) == 0),
1393         //       "Invalid alignment size");
1394 
1395         // When no alignment is specified, `uint.max` is the default
1396         // FIXME: alignment is 0 for structs templated members
1397         if (alignment.isDefault() || (tdparent && alignment.isUnknown()))
1398         {
1399             return;
1400         }
1401 
1402         buf.printf("#pragma pack(push, %d)", alignment.get());
1403         buf.writenl();
1404     }
1405 
1406     /// Ends a custom alignment section using `#pragma pack` if
1407     /// `alignment` specifies a custom alignment
1408     private void popAlignToBuffer(structalign_t alignment)
1409     {
1410         if (alignment.isDefault() || (tdparent && alignment.isUnknown()))
1411             return;
1412 
1413         buf.writestringln("#pragma pack(pop)");
1414     }
1415 
1416     override void visit(AST.ClassDeclaration cd)
1417     {
1418         debug (Debug_DtoH) mixin(traceVisit!cd);
1419 
1420         if (cd.baseClass && shouldEmit(cd))
1421             includeSymbol(cd.baseClass);
1422 
1423         if (!shouldEmitAndMarkVisited(cd))
1424             return;
1425 
1426         writeProtection(cd.visibility.kind);
1427 
1428         const classAsStruct = cd.cppmangle == CPPMANGLE.asStruct;
1429         buf.writestring(classAsStruct ? "struct " : "class ");
1430         writeIdentifier(cd);
1431 
1432         if (cd.storage_class & AST.STC.final_ || (tdparent && this.storageClass & AST.STC.final_))
1433             buf.writestring(" final");
1434 
1435         assert(cd.baseclasses);
1436 
1437         foreach (i, base; *cd.baseclasses)
1438         {
1439             buf.writestring(i == 0 ? " : public " : ", public ");
1440 
1441             // Base classes/interfaces might depend on template parameters,
1442             // e.g. class A(T) : B!T { ... }
1443             if (base.sym is null)
1444             {
1445                 base.type.accept(this);
1446             }
1447             else
1448             {
1449                 writeFullName(base.sym);
1450             }
1451         }
1452 
1453         if (!cd.members)
1454         {
1455             buf.writestring(";");
1456             buf.writenl();
1457             buf.writenl();
1458             return;
1459         }
1460 
1461         buf.writenl();
1462         buf.writestringln("{");
1463 
1464         const protStash = this.currentVisibility;
1465         this.currentVisibility = classAsStruct ? AST.Visibility.Kind.public_ : AST.Visibility.Kind.private_;
1466         scope (exit) this.currentVisibility = protStash;
1467 
1468         auto save = adparent;
1469         adparent = cd;
1470         buf.level++;
1471         foreach (m; *cd.members)
1472         {
1473             m.accept(this);
1474         }
1475         buf.level--;
1476         adparent = save;
1477 
1478         buf.writestringln("};");
1479         buf.writenl();
1480     }
1481 
1482     override void visit(AST.EnumDeclaration ed)
1483     {
1484         debug (Debug_DtoH) mixin(traceVisit!ed);
1485 
1486         if (!shouldEmitAndMarkVisited(ed))
1487             return;
1488 
1489         if (ed.isSpecial())
1490         {
1491             //ignored("%s because it is a special C++ type", ed.toPrettyChars());
1492             return;
1493         }
1494 
1495         // we need to know a bunch of stuff about the enum...
1496         bool isAnonymous = ed.ident is null;
1497         const isOpaque = !ed.members;
1498         AST.Type type = ed.memtype;
1499         if (!type && !isOpaque)
1500         {
1501             // check all keys have matching type
1502             foreach (_m; *ed.members)
1503             {
1504                 auto m = _m.isEnumMember();
1505                 if (!type)
1506                     type = m.type;
1507                 else if (m.type !is type)
1508                 {
1509                     type = null;
1510                     break;
1511                 }
1512             }
1513         }
1514         EnumKind kind = getEnumKind(type);
1515 
1516         if (isOpaque)
1517         {
1518             // Opaque enums were introduced in C++ 11 (workaround?)
1519             if (global.params.cplusplus < CppStdRevision.cpp11)
1520             {
1521                 ignored("%s because opaque enums require C++ 11", ed.toPrettyChars());
1522                 return;
1523             }
1524             // Opaque enum defaults to int but the type might not be set
1525             else if (!type)
1526             {
1527                 kind = EnumKind.Int;
1528             }
1529             // Cannot apply namespace workaround for non-integral types
1530             else if (kind != EnumKind.Int && kind != EnumKind.Numeric)
1531             {
1532                 ignored("enum %s because of its base type", ed.toPrettyChars());
1533                 return;
1534             }
1535         }
1536 
1537         // determine if this is an enum, or just a group of manifest constants
1538         bool manifestConstants = !isOpaque && (!type || (isAnonymous && kind == EnumKind.Other));
1539         assert(!manifestConstants || isAnonymous);
1540 
1541         writeProtection(ed.visibility.kind);
1542 
1543         // write the enum header
1544         if (!manifestConstants)
1545         {
1546             if (kind == EnumKind.Int || kind == EnumKind.Numeric)
1547             {
1548                 buf.writestring("enum");
1549                 // D enums are strong enums, but there exists only a direct mapping
1550                 // with 'enum class' from C++-11 onwards.
1551                 if (global.params.cplusplus >= CppStdRevision.cpp11)
1552                 {
1553                     if (!isAnonymous)
1554                     {
1555                         buf.writestring(" class ");
1556                         writeIdentifier(ed);
1557                     }
1558                     if (kind == EnumKind.Numeric)
1559                     {
1560                         buf.writestring(" : ");
1561                         determineEnumType(type).accept(this);
1562                     }
1563                 }
1564                 else if (!isAnonymous)
1565                 {
1566                     buf.writeByte(' ');
1567                     writeIdentifier(ed);
1568                 }
1569             }
1570             else
1571             {
1572                 buf.writestring("namespace");
1573                 if(!isAnonymous)
1574                 {
1575                     buf.writeByte(' ');
1576                     writeIdentifier(ed);
1577                 }
1578             }
1579             // Opaque enums have no members, hence skip the body
1580             if (isOpaque)
1581             {
1582                 buf.writestringln(";");
1583                 return;
1584             }
1585             else
1586             {
1587                 buf.writenl();
1588                 buf.writestringln("{");
1589             }
1590         }
1591 
1592         // emit constant for each member
1593         if (!manifestConstants)
1594             buf.level++;
1595 
1596         foreach (_m; *ed.members)
1597         {
1598             auto m = _m.isEnumMember();
1599             AST.Type memberType = type ? type : m.type;
1600             const EnumKind memberKind = type ? kind : getEnumKind(memberType);
1601 
1602             if (!manifestConstants && (kind == EnumKind.Int || kind == EnumKind.Numeric))
1603             {
1604                 // C++-98 compatible enums must use the typename as a prefix to avoid
1605                 // collisions with other identifiers in scope.  For consistency with D,
1606                 // the enum member `Type.member` is emitted as `Type_member` in C++-98.
1607                 if (!isAnonymous && global.params.cplusplus < CppStdRevision.cpp11)
1608                 {
1609                     writeIdentifier(ed);
1610                     buf.writeByte('_');
1611                 }
1612                 writeIdentifier(m, true);
1613                 buf.writestring(" = ");
1614 
1615                 auto ie = cast(AST.IntegerExp)m.value;
1616                 visitInteger(ie.toInteger(), memberType);
1617                 buf.writestring(",");
1618             }
1619             else if (global.params.cplusplus >= CppStdRevision.cpp11 &&
1620                      manifestConstants && (memberKind == EnumKind.Int || memberKind == EnumKind.Numeric))
1621             {
1622                 buf.writestring("enum : ");
1623                 determineEnumType(memberType).accept(this);
1624                 buf.writestring(" { ");
1625                 writeIdentifier(m, true);
1626                 buf.writestring(" = ");
1627 
1628                 auto ie = cast(AST.IntegerExp)m.value;
1629                 visitInteger(ie.toInteger(), memberType);
1630                 buf.writestring(" };");
1631             }
1632             else
1633             {
1634                 buf.writestring("static ");
1635                 auto target = determineEnumType(memberType);
1636                 target.accept(this);
1637                 buf.writestring(" const ");
1638                 writeIdentifier(m, true);
1639                 buf.writestring(" = ");
1640                 printExpressionFor(target, m.origValue);
1641                 buf.writestring(";");
1642             }
1643             buf.writenl();
1644         }
1645 
1646         if (!manifestConstants)
1647             buf.level--;
1648         // write the enum tail
1649         if (!manifestConstants)
1650             buf.writestring("};");
1651         buf.writenl();
1652         buf.writenl();
1653     }
1654 
1655     override void visit(AST.EnumMember em)
1656     {
1657         assert(em.ed);
1658 
1659         // Members of anonymous members are reachable without referencing the
1660         // EnumDeclaration, e.g. public import foo : someEnumMember;
1661         if (em.ed.isAnonymous())
1662         {
1663             visit(em.ed);
1664             return;
1665         }
1666 
1667         assert(false, "This node type should be handled in the EnumDeclaration");
1668     }
1669 
1670     /**
1671      * Prints a member/parameter/variable declaration into `buf`.
1672      *
1673      * Params:
1674      *   t        = the type (used if `this.origType` is null)
1675      *   s        = the symbol denoting the identifier
1676      *   canFixup = whether the identifier may be changed without affecting
1677      *              binary compatibility (forwarded to `writeIdentifier`)
1678      */
1679     private void typeToBuffer(AST.Type t, AST.Dsymbol s, const bool canFixup = false)
1680     {
1681         debug (Debug_DtoH)
1682         {
1683             printf("[typeToBuffer(AST.Type, AST.Dsymbol) enter] %s sym %s\n", t.toChars(), s.toChars());
1684             scope(exit) printf("[typeToBuffer(AST.Type, AST.Dsymbol) exit] %s sym %s\n", t.toChars(), s.toChars());
1685         }
1686 
1687         // The context pointer (represented as `ThisDeclaration`) is named
1688         // `this` but accessible via `outer`
1689         if (auto td = s.isThisDeclaration())
1690         {
1691             import dmd.id;
1692             this.ident = Id.outer;
1693         }
1694         else
1695             this.ident = s.ident;
1696 
1697         auto type = origType !is null ? origType : t;
1698         AST.Dsymbol customLength;
1699 
1700         // Check for quirks that are usually resolved during semantic
1701         if (tdparent)
1702         {
1703             // Declarations within template declarations might use TypeAArray
1704             // instead of TypeSArray when the length is not an IntegerExp,
1705             // e.g. int[SOME_CONSTANT]
1706             if (auto taa = type.isTypeAArray())
1707             {
1708                 // Try to resolve the symbol from the key if it's not an actual type
1709                 Identifier id;
1710                 if (auto ti = taa.index.isTypeIdentifier())
1711                     id = ti.ident;
1712 
1713                 if (id)
1714                 {
1715                     auto sym = findSymbol(id, adparent ? adparent : tdparent);
1716                     if (!sym)
1717                     {
1718                         // Couldn't resolve, assume actual AA
1719                     }
1720                     else if (AST.isType(sym))
1721                     {
1722                         // a real associative array, forward to visit
1723                     }
1724                     else if (auto vd = sym.isVarDeclaration())
1725                     {
1726                         // Actually a static array with length symbol
1727                         customLength = sym;
1728                         type = taa.next; // visit the element type, length is written below
1729                     }
1730                     else
1731                     {
1732                         printf("Resolved unexpected symbol while determining static array length: %s\n", sym.toChars());
1733                         fflush(stdout);
1734                         fatal();
1735                     }
1736                 }
1737             }
1738         }
1739         type.accept(this);
1740         if (this.ident)
1741         {
1742             buf.writeByte(' ');
1743             // Custom identifier doesn't need further checks
1744             if (this.ident !is s.ident)
1745                 buf.writestring(this.ident.toString());
1746             else
1747                 writeIdentifier(s, canFixup);
1748 
1749         }
1750         this.ident = null;
1751 
1752         // Size is either taken from the type or resolved above
1753         auto tsa = t.isTypeSArray();
1754         if (tsa || customLength)
1755         {
1756             buf.writeByte('[');
1757             if (tsa)
1758                 tsa.dim.accept(this);
1759             else
1760                 writeFullName(customLength);
1761             buf.writeByte(']');
1762         }
1763         else if (t.isTypeNoreturn())
1764             buf.writestring("[0]");
1765     }
1766 
1767     override void visit(AST.Type t)
1768     {
1769         debug (Debug_DtoH) mixin(traceVisit!t);
1770         printf("Invalid type: %s\n", t.toPrettyChars());
1771         assert(0);
1772     }
1773 
1774     override void visit(AST.TypeNoreturn t)
1775     {
1776         debug (Debug_DtoH) mixin(traceVisit!t);
1777 
1778         buf.writestring("/* noreturn */ char");
1779     }
1780 
1781     override void visit(AST.TypeIdentifier t)
1782     {
1783         debug (Debug_DtoH) mixin(traceVisit!t);
1784 
1785         // Try to resolve the referenced symbol
1786         if (auto sym = findSymbol(t.ident))
1787             ensureDeclared(outermostSymbol(sym));
1788 
1789         if (t.idents.length)
1790             buf.writestring("typename ");
1791 
1792         writeIdentifier(t.ident, t.loc, "type", tdparent !is null);
1793 
1794         foreach (arg; t.idents)
1795         {
1796             buf.writestring("::");
1797 
1798             import dmd.root.rootobject;
1799             // Is this even possible?
1800             if (arg.dyncast != DYNCAST.identifier)
1801             {
1802                 printf("arg.dyncast() = %d\n", arg.dyncast());
1803                 assert(false);
1804             }
1805             buf.writestring((cast(Identifier) arg).toChars());
1806         }
1807     }
1808 
1809     override void visit(AST.TypeNull t)
1810     {
1811         debug (Debug_DtoH) mixin(traceVisit!t);
1812 
1813         if (global.params.cplusplus >= CppStdRevision.cpp11)
1814             buf.writestring("nullptr_t");
1815         else
1816             buf.writestring("void*");
1817 
1818     }
1819 
1820     override void visit(AST.TypeTypeof t)
1821     {
1822         debug (Debug_DtoH) mixin(traceVisit!t);
1823 
1824         assert(t.exp);
1825 
1826         if (t.exp.type)
1827         {
1828             t.exp.type.accept(this);
1829         }
1830         else if (t.exp.isThisExp())
1831         {
1832             // Short circuit typeof(this) => <Aggregate name>
1833             assert(adparent);
1834             buf.writestring(adparent.ident.toChars());
1835         }
1836         else
1837         {
1838             // Relying on C++'s typeof might produce wrong results
1839             // but it's the best we've got here.
1840             buf.writestring("typeof(");
1841             t.exp.accept(this);
1842             buf.writeByte(')');
1843         }
1844     }
1845 
1846     override void visit(AST.TypeBasic t)
1847     {
1848         debug (Debug_DtoH) mixin(traceVisit!t);
1849 
1850         if (t.isConst() || t.isImmutable())
1851             buf.writestring("const ");
1852         string typeName;
1853         switch (t.ty)
1854         {
1855             case AST.Tvoid:     typeName = "void";      break;
1856             case AST.Tbool:     typeName = "bool";      break;
1857             case AST.Tchar:     typeName = "char";      break;
1858             case AST.Twchar:    typeName = "char16_t";  break;
1859             case AST.Tdchar:    typeName = "char32_t";  break;
1860             case AST.Tint8:     typeName = "int8_t";    break;
1861             case AST.Tuns8:     typeName = "uint8_t";   break;
1862             case AST.Tint16:    typeName = "int16_t";   break;
1863             case AST.Tuns16:    typeName = "uint16_t";  break;
1864             case AST.Tint32:    typeName = "int32_t";   break;
1865             case AST.Tuns32:    typeName = "uint32_t";  break;
1866             case AST.Tint64:    typeName = "int64_t";   break;
1867             case AST.Tuns64:    typeName = "uint64_t";  break;
1868             case AST.Tfloat32:  typeName = "float";     break;
1869             case AST.Tfloat64:  typeName = "double";    break;
1870             case AST.Tfloat80:
1871                 typeName = "_d_real";
1872                 hasReal = true;
1873                 break;
1874             case AST.Tcomplex32:  typeName = "_Complex float";  break;
1875             case AST.Tcomplex64:  typeName = "_Complex double"; break;
1876             case AST.Tcomplex80:
1877                 typeName = "_Complex _d_real";
1878                 hasReal = true;
1879                 break;
1880             // ???: This is not strictly correct, but it should be ignored
1881             // in all places where it matters most (variables, functions, ...).
1882             case AST.Timaginary32: typeName = "float";  break;
1883             case AST.Timaginary64: typeName = "double"; break;
1884             case AST.Timaginary80:
1885                 typeName = "_d_real";
1886                 hasReal = true;
1887                 break;
1888             default:
1889                 //t.print();
1890                 assert(0);
1891         }
1892         buf.writestring(typeName);
1893     }
1894 
1895     override void visit(AST.TypePointer t)
1896     {
1897         debug (Debug_DtoH) mixin(traceVisit!t);
1898 
1899         auto ts = t.next.isTypeStruct();
1900         if (ts && !strcmp(ts.sym.ident.toChars(), "__va_list_tag"))
1901         {
1902             buf.writestring("va_list");
1903             return;
1904         }
1905 
1906         // Pointer targets can be forward referenced
1907         const fwdSave = forwarding;
1908         forwarding = true;
1909         scope (exit) forwarding = fwdSave;
1910 
1911         t.next.accept(this);
1912         if (t.next.ty != AST.Tfunction)
1913             buf.writeByte('*');
1914         if (t.isConst() || t.isImmutable())
1915             buf.writestring(" const");
1916     }
1917 
1918     override void visit(AST.TypeSArray t)
1919     {
1920         debug (Debug_DtoH) mixin(traceVisit!t);
1921         t.next.accept(this);
1922     }
1923 
1924     override void visit(AST.TypeAArray t)
1925     {
1926         debug (Debug_DtoH) mixin(traceVisit!t);
1927         AST.Type.tvoidptr.accept(this);
1928     }
1929 
1930     override void visit(AST.TypeFunction tf)
1931     {
1932         debug (Debug_DtoH) mixin(traceVisit!tf);
1933 
1934         tf.next.accept(this);
1935         buf.writeByte('(');
1936         buf.writeByte('*');
1937         if (ident)
1938             buf.writestring(ident.toChars());
1939         ident = null;
1940         buf.writeByte(')');
1941         buf.writeByte('(');
1942         foreach (i, fparam; tf.parameterList)
1943         {
1944             if (i)
1945                 buf.writestring(", ");
1946             fparam.accept(this);
1947         }
1948         if (tf.parameterList.varargs)
1949         {
1950             if (tf.parameterList.parameters.dim && tf.parameterList.varargs == 1)
1951                 buf.writestring(", ");
1952             buf.writestring("...");
1953         }
1954         buf.writeByte(')');
1955     }
1956 
1957     ///  Writes the type that represents `ed` into `buf`.
1958     /// (Might not be `ed` for special enums or enums that were emitted as namespaces)
1959     private void enumToBuffer(AST.EnumDeclaration ed)
1960     {
1961         debug (Debug_DtoH) mixin(traceVisit!ed);
1962 
1963         if (ed.isSpecial())
1964         {
1965             if (ed.ident == DMDType.c_long)
1966                 buf.writestring("long");
1967             else if (ed.ident == DMDType.c_ulong)
1968                 buf.writestring("unsigned long");
1969             else if (ed.ident == DMDType.c_longlong)
1970                 buf.writestring("long long");
1971             else if (ed.ident == DMDType.c_ulonglong)
1972                 buf.writestring("unsigned long long");
1973             else if (ed.ident == DMDType.c_long_double)
1974                 buf.writestring("long double");
1975             else if (ed.ident == DMDType.c_char)
1976                 buf.writestring("char");
1977             else if (ed.ident == DMDType.c_wchar_t)
1978                 buf.writestring("wchar_t");
1979             else if (ed.ident == DMDType.c_complex_float)
1980                 buf.writestring("_Complex float");
1981             else if (ed.ident == DMDType.c_complex_double)
1982                 buf.writestring("_Complex double");
1983             else if (ed.ident == DMDType.c_complex_real)
1984                 buf.writestring("_Complex long double");
1985             else
1986             {
1987                 //ed.print();
1988                 assert(0);
1989             }
1990             return;
1991         }
1992 
1993         const kind = getEnumKind(ed.memtype);
1994 
1995         // Check if the enum was emitted as a real enum
1996         if (kind == EnumKind.Int || kind == EnumKind.Numeric)
1997         {
1998             writeFullName(ed);
1999         }
2000         else
2001         {
2002             // Use the base type if the enum was emitted as a namespace
2003             buf.printf("/* %s */ ", ed.ident.toChars());
2004             ed.memtype.accept(this);
2005         }
2006     }
2007 
2008     override void visit(AST.TypeEnum t)
2009     {
2010         debug (Debug_DtoH) mixin(traceVisit!t);
2011 
2012         if (t.isConst() || t.isImmutable())
2013             buf.writestring("const ");
2014         enumToBuffer(t.sym);
2015     }
2016 
2017     override void visit(AST.TypeStruct t)
2018     {
2019         debug (Debug_DtoH) mixin(traceVisit!t);
2020 
2021         if (t.isConst() || t.isImmutable())
2022             buf.writestring("const ");
2023         writeFullName(t.sym);
2024     }
2025 
2026     override void visit(AST.TypeDArray t)
2027     {
2028         debug (Debug_DtoH) mixin(traceVisit!t);
2029 
2030         if (t.isConst() || t.isImmutable())
2031             buf.writestring("const ");
2032         buf.writestring("_d_dynamicArray< ");
2033         t.next.accept(this);
2034         buf.writestring(" >");
2035     }
2036 
2037     override void visit(AST.TypeInstance t)
2038     {
2039         visitTi(t.tempinst);
2040     }
2041 
2042     private void visitTi(AST.TemplateInstance ti)
2043     {
2044         debug (Debug_DtoH) mixin(traceVisit!ti);
2045 
2046         // Ensure that the TD appears before the instance
2047         if (auto td = findTemplateDeclaration(ti))
2048             ensureDeclared(td);
2049 
2050         foreach (o; *ti.tiargs)
2051         {
2052             if (!AST.isType(o))
2053                 return;
2054         }
2055         buf.writestring(ti.name.toChars());
2056         buf.writeByte('<');
2057         foreach (i, o; *ti.tiargs)
2058         {
2059             if (i)
2060                 buf.writestring(", ");
2061             if (auto tt = AST.isType(o))
2062             {
2063                 tt.accept(this);
2064             }
2065             else
2066             {
2067                 //ti.print();
2068                 //o.print();
2069                 assert(0);
2070             }
2071         }
2072         buf.writestring(" >");
2073     }
2074 
2075     override void visit(AST.TemplateDeclaration td)
2076     {
2077         debug (Debug_DtoH) mixin(traceVisit!td);
2078 
2079         if (!shouldEmitAndMarkVisited(td))
2080             return;
2081 
2082         if (!td.parameters || !td.onemember || (!td.onemember.isStructDeclaration && !td.onemember.isClassDeclaration && !td.onemember.isFuncDeclaration))
2083         {
2084             visit(cast(AST.Dsymbol)td);
2085             return;
2086         }
2087 
2088         // Explicitly disallow templates with non-type parameters or specialization.
2089         foreach (p; *td.parameters)
2090         {
2091             if (!p.isTemplateTypeParameter() || p.specialization())
2092             {
2093                 visit(cast(AST.Dsymbol)td);
2094                 return;
2095             }
2096         }
2097 
2098         auto save = tdparent;
2099         tdparent = td;
2100         const bookmark = buf.length;
2101         printTemplateParams(td);
2102 
2103         const oldIgnored = this.ignoredCounter;
2104         td.onemember.accept(this);
2105 
2106         // Remove "template<...>" if the symbol could not be emitted
2107         if (oldIgnored != this.ignoredCounter)
2108             buf.setsize(bookmark);
2109 
2110         tdparent = save;
2111     }
2112 
2113     /// Writes the template<...> header for the supplied template declaration
2114     private void printTemplateParams(const AST.TemplateDeclaration td)
2115     {
2116         buf.writestring("template <");
2117         bool first = true;
2118         foreach (p; *td.parameters)
2119         {
2120             if (first)
2121                 first = false;
2122             else
2123                 buf.writestring(", ");
2124             buf.writestring("typename ");
2125             writeIdentifier(p.ident, p.loc, "template parameter", true);
2126         }
2127         buf.writestringln(">");
2128     }
2129 
2130     /// Emit declarations of the TemplateMixin in the current scope
2131     override void visit(AST.TemplateMixin tm)
2132     {
2133         debug (Debug_DtoH) mixin(traceVisit!tm);
2134 
2135         auto members = tm.members;
2136 
2137         // members are missing for instances inside of TemplateDeclarations, e.g.
2138         // template Foo(T) { mixin Bar!T; }
2139         if (!members)
2140         {
2141             if (auto td = findTemplateDeclaration(tm))
2142                 members = td.members; // Emit members of the template
2143             else
2144                 return; // Cannot emit mixin
2145         }
2146 
2147         foreach (s; *members)
2148         {
2149             // kind is undefined without semantic
2150             const kind = s.visible().kind;
2151             if (kind == AST.Visibility.Kind.public_ || kind == AST.Visibility.Kind.undefined)
2152                 s.accept(this);
2153         }
2154     }
2155 
2156     /**
2157      * Finds a symbol with the identifier `name` by iterating the linked list of parent
2158      * symbols, starting from `context`.
2159      *
2160      * Returns: the symbol or `null` if missing
2161      */
2162     private AST.Dsymbol findSymbol(Identifier name, AST.Dsymbol context)
2163     {
2164         // Follow the declaration context
2165         for (auto par = context; par; par = par.toParentDecl())
2166         {
2167             // Check that `name` doesn't refer to a template parameter
2168             if (auto td = par.isTemplateDeclaration())
2169             {
2170                 foreach (const p; *td.parameters)
2171                 {
2172                     if (p.ident == name)
2173                         return null;
2174                 }
2175             }
2176 
2177             if (auto mem = findMember(par, name))
2178             {
2179                 return mem;
2180             }
2181         }
2182         return null;
2183     }
2184 
2185     /// ditto
2186     private AST.Dsymbol findSymbol(Identifier name)
2187     {
2188         AST.Dsymbol sym;
2189         if (adparent)
2190             sym = findSymbol(name, adparent);
2191 
2192         if (!sym && tdparent)
2193             sym = findSymbol(name, tdparent);
2194 
2195         return sym;
2196     }
2197 
2198     /// Finds the template declaration for instance `ti`
2199     private AST.TemplateDeclaration findTemplateDeclaration(AST.TemplateInstance ti)
2200     {
2201         if (ti.tempdecl)
2202             return ti.tempdecl.isTemplateDeclaration();
2203 
2204         assert(tdparent); // Only missing inside of templates
2205 
2206         // Search for the TemplateDeclaration, starting from the enclosing scope
2207         // if known or the enclosing template.
2208         auto sym = findSymbol(ti.name, ti.parent ? ti.parent : tdparent);
2209         return sym ? sym.isTemplateDeclaration() : null;
2210     }
2211 
2212     override void visit(AST.TypeClass t)
2213     {
2214         debug (Debug_DtoH) mixin(traceVisit!t);
2215 
2216         // Classes are emitted as pointer and hence can be forwarded
2217         const fwdSave = forwarding;
2218         forwarding = true;
2219         scope (exit) forwarding = fwdSave;
2220 
2221         if (t.isConst() || t.isImmutable())
2222             buf.writestring("const ");
2223         writeFullName(t.sym);
2224         buf.writeByte('*');
2225         if (t.isConst() || t.isImmutable())
2226             buf.writestring(" const");
2227     }
2228 
2229     /**
2230      * Writes the function signature to `buf`.
2231      *
2232      * Params:
2233      *   fd     = the function to print
2234      *   tf     = fd's type
2235      */
2236     private void funcToBuffer(AST.TypeFunction tf, AST.FuncDeclaration fd)
2237     {
2238         debug (Debug_DtoH)
2239         {
2240             printf("[funcToBuffer(AST.TypeFunction) enter] %s\n", fd.toChars());
2241             scope(exit) printf("[funcToBuffer(AST.TypeFunction) exit] %s\n", fd.toChars());
2242         }
2243 
2244         auto originalType = cast(AST.TypeFunction)fd.originalType;
2245 
2246         if (fd.isCtorDeclaration() || fd.isDtorDeclaration())
2247         {
2248             if (fd.isDtorDeclaration())
2249             {
2250                 buf.writeByte('~');
2251             }
2252             buf.writestring(adparent.toChars());
2253             if (!tf)
2254             {
2255                 assert(fd.isDtorDeclaration());
2256                 buf.writestring("()");
2257                 return;
2258             }
2259         }
2260         else
2261         {
2262             import dmd.root.string : toDString;
2263             assert(tf.next, fd.loc.toChars().toDString());
2264 
2265             tf.next == AST.Type.tsize_t ? originalType.next.accept(this) : tf.next.accept(this);
2266             if (tf.isref)
2267                 buf.writeByte('&');
2268             buf.writeByte(' ');
2269             writeIdentifier(fd);
2270         }
2271 
2272         buf.writeByte('(');
2273         foreach (i, fparam; tf.parameterList)
2274         {
2275             if (i)
2276                 buf.writestring(", ");
2277             if (fparam.type == AST.Type.tsize_t && originalType)
2278             {
2279                 fparam = originalType.parameterList[i];
2280             }
2281             fparam.accept(this);
2282         }
2283         if (tf.parameterList.varargs)
2284         {
2285             if (tf.parameterList.parameters.dim && tf.parameterList.varargs == 1)
2286                 buf.writestring(", ");
2287             buf.writestring("...");
2288         }
2289         buf.writeByte(')');
2290     }
2291 
2292     override void visit(AST.Parameter p)
2293     {
2294         debug (Debug_DtoH) mixin(traceVisit!p);
2295 
2296         ident = p.ident;
2297 
2298         {
2299             // Reference parameters can be forwarded
2300             const fwdStash = this.forwarding;
2301             this.forwarding = !!(p.storageClass & AST.STC.ref_);
2302             p.type.accept(this);
2303             this.forwarding = fwdStash;
2304         }
2305 
2306         if (p.storageClass & AST.STC.ref_)
2307             buf.writeByte('&');
2308         buf.writeByte(' ');
2309         if (ident)
2310             // FIXME: Parameter is missing a Loc
2311             writeIdentifier(ident, Loc.initial, "parameter", true);
2312         ident = null;
2313 
2314         if (p.defaultArg)
2315         {
2316             //printf("%s %d\n", p.defaultArg.toChars, p.defaultArg.op);
2317             buf.writestring(" = ");
2318             printExpressionFor(p.type, p.defaultArg);
2319         }
2320     }
2321 
2322     /**
2323      * Prints `exp` as an expression of type `target` while inserting
2324      * appropriate code when implicit conversion does not translate
2325      * directly to C++, e.g. from an enum to its base type.
2326      *
2327      * Params:
2328      *   target = the type `exp` is converted to
2329      *   exp    = the expression to print
2330      *   isCtor = if `exp` is a ctor argument
2331      */
2332     private void printExpressionFor(AST.Type target, AST.Expression exp, const bool isCtor = false)
2333     {
2334         /// Determines if a static_cast is required
2335         static bool needsCast(AST.Type target, AST.Expression exp)
2336         {
2337             // import std.stdio;
2338             // writefln("%s:%s: target = %s, type = %s (%s)", exp.loc.linnum, exp.loc.charnum, target, exp.type, exp.op);
2339 
2340             auto source = exp.type;
2341 
2342             // DotVarExp resolve conversions, e.g from an enum to its base type
2343             if (auto dve = exp.isDotVarExp())
2344                 source = dve.var.type;
2345 
2346             if (!source)
2347                 // Defensively assume that the cast is required
2348                 return true;
2349 
2350             // Conversions from enum class to base type require static_cast
2351             if (global.params.cplusplus >= CppStdRevision.cpp11 &&
2352                 source.isTypeEnum && !target.isTypeEnum)
2353                 return true;
2354 
2355             return false;
2356         }
2357 
2358         // Slices are emitted as a special struct, hence we need to fix up
2359         // any expression initialising a slice variable/member
2360         if (auto ta = target.isTypeDArray())
2361         {
2362             if (exp.isNullExp())
2363             {
2364                 if (isCtor)
2365                 {
2366                     // Don't emit, use default ctor
2367                 }
2368                 else if (global.params.cplusplus >= CppStdRevision.cpp11)
2369                 {
2370                     // Prefer initializer list
2371                     buf.writestring("{}");
2372                 }
2373                 else
2374                 {
2375                     // Write __d_dynamic_array<TYPE>()
2376                     visit(ta);
2377                     buf.writestring("()");
2378                 }
2379                 return;
2380             }
2381 
2382             if (auto se = exp.isStringExp())
2383             {
2384                 // Rewrite as <length> + <literal> pair optionally
2385                 // wrapped in a initializer list/ctor call
2386 
2387                 const initList = global.params.cplusplus >= CppStdRevision.cpp11;
2388                 if (!isCtor)
2389                 {
2390                     if (initList)
2391                         buf.writestring("{ ");
2392                     else
2393                     {
2394                         visit(ta);
2395                         buf.writestring("( ");
2396                     }
2397                 }
2398 
2399                 buf.printf("%zu, ", se.len);
2400                 visit(se);
2401 
2402                 if (!isCtor)
2403                     buf.writestring(initList ? " }" : " )");
2404 
2405                 return;
2406             }
2407         }
2408         else if (auto ce = exp.isCastExp())
2409         {
2410             buf.writeByte('(');
2411             if (ce.to)
2412                 ce.to.accept(this);
2413             else if (ce.e1.type)
2414                 // Try the expression type with modifiers in case of cast(const) in templates
2415                 ce.e1.type.castMod(ce.mod).accept(this);
2416             else
2417                 // Fallback, not necessarily correct but the best we've got here
2418                 target.accept(this);
2419             buf.writestring(") ");
2420             ce.e1.accept(this);
2421         }
2422         else if (needsCast(target, exp))
2423         {
2424             buf.writestring("static_cast<");
2425             target.accept(this);
2426             buf.writestring(">(");
2427             exp.accept(this);
2428             buf.writeByte(')');
2429         }
2430         else
2431         {
2432             exp.accept(this);
2433         }
2434     }
2435 
2436     override void visit(AST.Expression e)
2437     {
2438         debug (Debug_DtoH) mixin(traceVisit!e);
2439 
2440         // Valid in most cases, others should be overriden below
2441         // to use the appropriate operators  (:: and ->)
2442         buf.writestring(e.toString());
2443     }
2444 
2445     override void visit(AST.UnaExp e)
2446     {
2447         debug (Debug_DtoH) mixin(traceVisit!e);
2448 
2449         buf.writestring(expToString(e.op));
2450         e.e1.accept(this);
2451     }
2452 
2453     override void visit(AST.BinExp e)
2454     {
2455         debug (Debug_DtoH) mixin(traceVisit!e);
2456 
2457         e.e1.accept(this);
2458         buf.writeByte(' ');
2459         buf.writestring(expToString(e.op));
2460         buf.writeByte(' ');
2461         e.e2.accept(this);
2462     }
2463 
2464     /// Translates operator `op` into the C++ representation
2465     private extern(D) static string expToString(const EXP op)
2466     {
2467         switch (op) with (EXP)
2468         {
2469             case identity:      return "==";
2470             case notIdentity:   return "!=";
2471             default:
2472                 return EXPtoString(op);
2473         }
2474     }
2475 
2476     override void visit(AST.VarExp e)
2477     {
2478         debug (Debug_DtoH) mixin(traceVisit!e);
2479 
2480         // Local members don't need another prefix and might've been renamed
2481         if (e.var.isThis())
2482         {
2483             includeSymbol(e.var);
2484             writeIdentifier(e.var, true);
2485         }
2486         else
2487             writeFullName(e.var);
2488     }
2489 
2490     /// Partially prints the FQN including parent aggregates
2491     private void printPrefix(AST.Dsymbol var)
2492     {
2493         if (!var || var is adparent || var.isModule())
2494             return;
2495 
2496         writeFullName(var);
2497         buf.writestring("::");
2498     }
2499 
2500     override void visit(AST.CallExp e)
2501     {
2502         debug (Debug_DtoH) mixin(traceVisit!e);
2503 
2504         // Dereferencing function pointers requires additional braces: (*f)(args)
2505         const isFp = e.e1.isPtrExp();
2506         if (isFp)
2507             buf.writeByte('(');
2508         else if (e.f)
2509             includeSymbol(outermostSymbol(e.f));
2510 
2511         e.e1.accept(this);
2512 
2513         if (isFp) buf.writeByte(')');
2514 
2515         assert(e.arguments);
2516         buf.writeByte('(');
2517         foreach (i, arg; *e.arguments)
2518         {
2519             if (i)
2520                 buf.writestring(", ");
2521             arg.accept(this);
2522         }
2523         buf.writeByte(')');
2524     }
2525 
2526     override void visit(AST.DotVarExp e)
2527     {
2528         debug (Debug_DtoH) mixin(traceVisit!e);
2529 
2530         if (auto sym = symbolFromType(e.e1.type))
2531             includeSymbol(outermostSymbol(sym));
2532 
2533         // Accessing members through a pointer?
2534         if (auto pe = e.e1.isPtrExp)
2535         {
2536             pe.e1.accept(this);
2537             buf.writestring("->");
2538         }
2539         else
2540         {
2541             e.e1.accept(this);
2542             buf.writeByte('.');
2543         }
2544 
2545         // Should only be used to access non-static members
2546         assert(e.var.isThis());
2547 
2548         writeIdentifier(e.var, true);
2549     }
2550 
2551     override void visit(AST.DotIdExp e)
2552     {
2553         debug (Debug_DtoH) mixin(traceVisit!e);
2554 
2555         e.e1.accept(this);
2556         buf.writestring("::");
2557         buf.writestring(e.ident.toChars());
2558     }
2559 
2560     override void visit(AST.ScopeExp e)
2561     {
2562         debug (Debug_DtoH) mixin(traceVisit!e);
2563 
2564         // Usually a template instance in a TemplateDeclaration
2565         if (auto ti = e.sds.isTemplateInstance())
2566             visitTi(ti);
2567         else
2568             writeFullName(e.sds);
2569     }
2570 
2571     override void visit(AST.NullExp e)
2572     {
2573         debug (Debug_DtoH) mixin(traceVisit!e);
2574 
2575         if (global.params.cplusplus >= CppStdRevision.cpp11)
2576             buf.writestring("nullptr");
2577         else
2578             buf.writestring("NULL");
2579     }
2580 
2581     override void visit(AST.ArrayLiteralExp e)
2582     {
2583         debug (Debug_DtoH) mixin(traceVisit!e);
2584         buf.writestring("arrayliteral");
2585     }
2586 
2587     override void visit(AST.StringExp e)
2588     {
2589         debug (Debug_DtoH) mixin(traceVisit!e);
2590 
2591         if (e.sz == 2)
2592             buf.writeByte('u');
2593         else if (e.sz == 4)
2594             buf.writeByte('U');
2595         buf.writeByte('"');
2596 
2597         foreach (i; 0 .. e.len)
2598         {
2599             writeCharLiteral(*buf, e.getCodeUnit(i));
2600         }
2601         buf.writeByte('"');
2602     }
2603 
2604     override void visit(AST.RealExp e)
2605     {
2606         debug (Debug_DtoH) mixin(traceVisit!e);
2607 
2608         import dmd.root.ctfloat : CTFloat;
2609 
2610         // Special case NaN and Infinity because floatToBuffer
2611         // uses D literals (`nan` and `infinity`)
2612         if (CTFloat.isNaN(e.value))
2613         {
2614             buf.writestring("NAN");
2615         }
2616         else if (CTFloat.isInfinity(e.value))
2617         {
2618             if (e.value < CTFloat.zero)
2619                 buf.writeByte('-');
2620             buf.writestring("INFINITY");
2621         }
2622         else
2623         {
2624             import dmd.hdrgen;
2625             // Hex floating point literals were introduced in C++ 17
2626             const allowHex = global.params.cplusplus >= CppStdRevision.cpp17;
2627             floatToBuffer(e.type, e.value, buf, allowHex);
2628         }
2629     }
2630 
2631     override void visit(AST.IntegerExp e)
2632     {
2633         debug (Debug_DtoH) mixin(traceVisit!e);
2634         visitInteger(e.toInteger, e.type);
2635     }
2636 
2637     /// Writes `v` as type `t` into `buf`
2638     private void visitInteger(dinteger_t v, AST.Type t)
2639     {
2640         debug (Debug_DtoH) mixin(traceVisit!t);
2641 
2642         switch (t.ty)
2643         {
2644             case AST.Tenum:
2645                 auto te = cast(AST.TypeEnum)t;
2646                 buf.writestring("(");
2647                 enumToBuffer(te.sym);
2648                 buf.writestring(")");
2649                 visitInteger(v, te.sym.memtype);
2650                 break;
2651             case AST.Tbool:
2652                 buf.writestring(v ? "true" : "false");
2653                 break;
2654             case AST.Tint8:
2655                 buf.printf("%d", cast(byte)v);
2656                 break;
2657             case AST.Tuns8:
2658                 buf.printf("%uu", cast(ubyte)v);
2659                 break;
2660             case AST.Tint16:
2661                 buf.printf("%d", cast(short)v);
2662                 break;
2663             case AST.Tuns16:
2664             case AST.Twchar:
2665                 buf.printf("%uu", cast(ushort)v);
2666                 break;
2667             case AST.Tint32:
2668             case AST.Tdchar:
2669                 buf.printf("%d", cast(int)v);
2670                 break;
2671             case AST.Tuns32:
2672                 buf.printf("%uu", cast(uint)v);
2673                 break;
2674             case AST.Tint64:
2675                 buf.printf("%lldLL", v);
2676                 break;
2677             case AST.Tuns64:
2678                 buf.printf("%lluLLU", v);
2679                 break;
2680             case AST.Tchar:
2681                 if (v > 0x20 && v < 0x80)
2682                     buf.printf("'%c'", cast(int)v);
2683                 else
2684                     buf.printf("%uu", cast(ubyte)v);
2685                 break;
2686             default:
2687                 //t.print();
2688                 assert(0);
2689         }
2690     }
2691 
2692     override void visit(AST.StructLiteralExp sle)
2693     {
2694         debug (Debug_DtoH) mixin(traceVisit!sle);
2695 
2696         const isUnion = sle.sd.isUnionDeclaration();
2697         sle.sd.type.accept(this);
2698         buf.writeByte('(');
2699         foreach(i, e; *sle.elements)
2700         {
2701             if (i)
2702                 buf.writestring(", ");
2703 
2704             auto vd = sle.sd.fields[i];
2705 
2706             // Expression may be null for unspecified elements
2707             if (!e)
2708                 e = findDefaultInitializer(vd);
2709 
2710             printExpressionFor(vd.type, e);
2711 
2712             // Only emit the initializer of the first union member
2713             if (isUnion)
2714                 break;
2715         }
2716         buf.writeByte(')');
2717     }
2718 
2719     /// Finds the default initializer for the given VarDeclaration
2720     private static AST.Expression findDefaultInitializer(AST.VarDeclaration vd)
2721     {
2722         if (vd._init && !vd._init.isVoidInitializer())
2723             return AST.initializerToExpression(vd._init);
2724         else if (auto ts = vd.type.isTypeStruct())
2725         {
2726             if (!ts.sym.noDefaultCtor && !ts.sym.isUnionDeclaration())
2727             {
2728                 // Generate a call to the default constructor that we've generated.
2729                 auto sle = new AST.StructLiteralExp(Loc.initial, ts.sym, new AST.Expressions(0));
2730                 sle.type = vd.type;
2731                 return sle;
2732             }
2733             else
2734                 return vd.type.defaultInitLiteral(Loc.initial);
2735         }
2736         else
2737             return vd.type.defaultInitLiteral(Loc.initial);
2738     }
2739 
2740     static if (__VERSION__ < 2092)
2741     {
2742         private void ignored(const char* format, ...) nothrow
2743         {
2744             this.ignoredCounter++;
2745 
2746             import core.stdc.stdarg;
2747             if (!printIgnored)
2748                 return;
2749 
2750             va_list ap;
2751             va_start(ap, format);
2752             buf.writestring("// Ignored ");
2753             buf.vprintf(format, ap);
2754             buf.writenl();
2755             va_end(ap);
2756         }
2757     }
2758     else
2759     {
2760         /// Writes a formatted message into `buf` if `printIgnored` is true
2761         /// and increments `ignoredCounter`
2762         pragma(printf)
2763         private void ignored(const char* format, ...) nothrow
2764         {
2765             this.ignoredCounter++;
2766 
2767             import core.stdc.stdarg;
2768             if (!printIgnored)
2769                 return;
2770 
2771             va_list ap;
2772             va_start(ap, format);
2773             buf.writestring("// Ignored ");
2774             buf.vprintf(format, ap);
2775             buf.writenl();
2776             va_end(ap);
2777         }
2778     }
2779 
2780     /**
2781      * Determines whether `s` should be emitted. This requires that `sym`
2782      * - is `extern(C[++]`)
2783      * - is not instantiated from a template (visits the `TemplateDeclaration` instead)
2784      *
2785      * Params:
2786      *   sym = the symbol
2787      *
2788      * Returns: whether `sym` should be emitted
2789      */
2790     private bool shouldEmit(AST.Dsymbol sym)
2791     {
2792         import dmd.aggregate : ClassKind;
2793         debug (Debug_DtoH)
2794         {
2795             printf("[shouldEmitAndMarkVisited enter] %s\n", sym.toPrettyChars());
2796             scope(exit) printf("[shouldEmitAndMarkVisited exit] %s\n", sym.toPrettyChars());
2797         }
2798 
2799         // Template *instances* should not be emitted
2800         if (sym.isInstantiated())
2801             return false;
2802 
2803         // Matching linkage (except extern(C) classes which don't make sense)
2804         if (linkage == LINK.cpp || (linkage == LINK.c && !sym.isClassDeclaration()))
2805             return true;
2806 
2807         // Check against the internal information which might be missing, e.g. inside of template declarations
2808         if (auto dec = sym.isDeclaration())
2809         {
2810             const l = dec.resolvedLinkage();
2811             return l == LINK.cpp || l == LINK.c;
2812         }
2813 
2814         if (auto ad = sym.isAggregateDeclaration())
2815             return ad.classKind == ClassKind.cpp;
2816 
2817         return false;
2818     }
2819 
2820     /**
2821      * Determines whether `s` should be emitted. This requires that `sym`
2822      * - was not visited before
2823      * - is `extern(C[++]`)
2824      * - is not instantiated from a template (visits the `TemplateDeclaration` instead)
2825      * The result is cached in the visited nodes array.
2826      *
2827      * Params:
2828      *   sym = the symbol
2829      *
2830      * Returns: whether `sym` should be emitted
2831      **/
2832     private bool shouldEmitAndMarkVisited(AST.Dsymbol sym)
2833     {
2834         debug (Debug_DtoH)
2835         {
2836             printf("[shouldEmitAndMarkVisited enter] %s\n", sym.toPrettyChars());
2837             scope(exit) printf("[shouldEmitAndMarkVisited exit] %s\n", sym.toPrettyChars());
2838         }
2839 
2840         auto statePtr = (cast(void*) sym) in visited;
2841 
2842          // `sym` was already emitted or skipped and isn't required
2843         if (statePtr && (*statePtr || !mustEmit))
2844             return false;
2845 
2846         // Template *instances* should not be emitted, forward to the declaration
2847         if (auto ti = sym.isInstantiated())
2848         {
2849             auto td = findTemplateDeclaration(ti);
2850             assert(td);
2851             visit(td);
2852             return false;
2853         }
2854 
2855         // Required or matching linkage (except extern(C) classes which don't make sense)
2856         bool res = mustEmit || linkage == LINK.cpp || (linkage == LINK.c && !sym.isClassDeclaration());
2857         if (!res)
2858         {
2859             // Check against the internal information which might be missing, e.g. inside of template declarations
2860             if (auto dec = sym.isDeclaration())
2861             {
2862                 const l = dec.resolvedLinkage();
2863                 res = (l == LINK.cpp || l == LINK.c);
2864             }
2865         }
2866 
2867         // Remember result for later calls
2868         if (statePtr)
2869             *statePtr = res;
2870         else
2871             visited[(cast(void*) sym)] = res;
2872 
2873         // Print a warning when the symbol is ignored for the first time
2874         // Might not be correct if it is required by symbol the is visited
2875         // AFTER the current node
2876         if (!statePtr && !res)
2877             ignored("%s %s because of linkage", sym.kind(), sym.toPrettyChars());
2878 
2879         return res;
2880     }
2881 
2882     /**
2883      * Ensures that `sym` is declared before the current position in `buf` by
2884      * either creating a forward reference in `fwdbuf` if possible or
2885      * calling `includeSymbol` to emit the entire declaration into `donebuf`.
2886      */
2887     private void ensureDeclared(AST.Dsymbol sym)
2888     {
2889         auto par = sym.toParent2();
2890         auto ed = sym.isEnumDeclaration();
2891 
2892         // Eagerly include the symbol if we cannot create a valid forward declaration
2893         // Forwarding of scoped enums requires C++11 or above
2894         if (!forwarding || (par && !par.isModule()) || (ed && global.params.cplusplus < CppStdRevision.cpp11))
2895         {
2896             // Emit the entire enclosing declaration if any
2897             includeSymbol(outermostSymbol(sym));
2898             return;
2899         }
2900 
2901         auto ti = sym.isInstantiated();
2902         auto td = ti ? findTemplateDeclaration(ti) : null;
2903         auto check = cast(void*) (td ? td : sym);
2904 
2905         // Omit redundant fwd-declaration if we already emitted the entire declaration
2906         if (visited.get(check, false))
2907             return;
2908 
2909         // Already created a fwd-declaration?
2910         if (check in forwarded)
2911             return;
2912         forwarded[check] = true;
2913 
2914         // Print template<...>
2915         if (ti)
2916         {
2917             auto bufSave = buf;
2918             buf = fwdbuf;
2919             printTemplateParams(td);
2920             buf = bufSave;
2921         }
2922 
2923         // Determine the kind of symbol that is forwared: struct, ...
2924         const(char)* kind;
2925 
2926         if (auto ad = sym.isAggregateDeclaration())
2927         {
2928             // Look for extern(C++, class) <some aggregate>
2929             if (ad.cppmangle == CPPMANGLE.def)
2930                 kind = ad.kind();
2931             else if (ad.cppmangle == CPPMANGLE.asStruct)
2932                 kind =  "struct";
2933             else
2934                 kind = "class";
2935         }
2936         else if (ed)
2937         {
2938             // Only called from enumToBuffer, so should always be emitted as an actual enum
2939             kind = "enum class";
2940         }
2941         else
2942             kind = sym.kind(); // Should be unreachable but just to be sure
2943 
2944         fwdbuf.writestring(kind);
2945         fwdbuf.writeByte(' ');
2946         fwdbuf.writestring(sym.toChars());
2947         fwdbuf.writestringln(";");
2948     }
2949 
2950     /**
2951      * Writes the qualified name of `sym` into `buf` including parent
2952      * symbols and template parameters.
2953      *
2954      * Params:
2955      *   sym         = the symbol
2956      *   mustInclude = whether sym may not be forward declared
2957      */
2958     private void writeFullName(AST.Dsymbol sym, const bool mustInclude = false)
2959     in
2960     {
2961         assert(sym);
2962         assert(sym.ident, sym.toString());
2963         // Should never be called directly with a TI, only onemember
2964         assert(!sym.isTemplateInstance(), sym.toString());
2965     }
2966     do
2967     {
2968         debug (Debug_DtoH)
2969         {
2970             printf("[writeFullName enter] %s\n", sym.toPrettyChars());
2971             scope(exit) printf("[writeFullName exit] %s\n", sym.toPrettyChars());
2972         }
2973 
2974         // Explicit `pragma(mangle, "<some string>` overrides the declared name
2975         if (auto mn = getMangleOverride(sym))
2976             return buf.writestring(mn);
2977 
2978         /// Checks whether `sym` is nested in `par` and hence doesn't need the FQN
2979         static bool isNestedIn(AST.Dsymbol sym, AST.Dsymbol par)
2980         {
2981             while (par)
2982             {
2983                 if (sym is par)
2984                     return true;
2985                 par = par.toParent();
2986             }
2987             return false;
2988         }
2989         AST.TemplateInstance ti;
2990         bool nested;
2991 
2992         // Check if the `sym` is nested into another symbol and hence requires `Parent::sym`
2993         if (auto par = sym.toParent())
2994         {
2995             // toParent() yields the template instance if `sym` is the onemember of a TI
2996             ti = par.isTemplateInstance();
2997 
2998             // Skip the TI because Foo!int.Foo is folded into Foo<int>
2999             if (ti) par = ti.toParent();
3000 
3001             // Prefix the name with any enclosing declaration
3002             // Stop at either module or enclosing aggregate
3003             nested = !par.isModule();
3004             if (nested && !isNestedIn(par, adparent))
3005             {
3006                 writeFullName(par, true);
3007                 buf.writestring("::");
3008             }
3009         }
3010 
3011         if (!nested)
3012         {
3013             // Cannot forward the symbol when called recursively
3014             // for a nested symbol
3015             if (mustInclude)
3016                 includeSymbol(sym);
3017             else
3018                 ensureDeclared(sym);
3019         }
3020 
3021         if (ti)
3022             visitTi(ti);
3023         else
3024             buf.writestring(sym.ident.toString());
3025     }
3026 
3027     /// Returns: Explicit mangling for `sym` if present
3028     extern(D) static const(char)[] getMangleOverride(const AST.Dsymbol sym)
3029     {
3030         if (auto decl = sym.isDeclaration())
3031             return decl.mangleOverride;
3032 
3033         return null;
3034     }
3035 }
3036 
3037 /// Namespace for identifiers used to represent special enums in C++
3038 struct DMDType
3039 {
3040     __gshared Identifier c_long;
3041     __gshared Identifier c_ulong;
3042     __gshared Identifier c_longlong;
3043     __gshared Identifier c_ulonglong;
3044     __gshared Identifier c_long_double;
3045     __gshared Identifier c_char;
3046     __gshared Identifier c_wchar_t;
3047     __gshared Identifier c_complex_float;
3048     __gshared Identifier c_complex_double;
3049     __gshared Identifier c_complex_real;
3050 
3051     static void _init()
3052     {
3053         c_long          = Identifier.idPool("__c_long");
3054         c_ulong         = Identifier.idPool("__c_ulong");
3055         c_longlong      = Identifier.idPool("__c_longlong");
3056         c_ulonglong     = Identifier.idPool("__c_ulonglong");
3057         c_long_double   = Identifier.idPool("__c_long_double");
3058         c_wchar_t       = Identifier.idPool("__c_wchar_t");
3059         c_char          = Identifier.idPool("__c_char");
3060         c_complex_float  = Identifier.idPool("__c_complex_float");
3061         c_complex_double = Identifier.idPool("__c_complex_double");
3062         c_complex_real = Identifier.idPool("__c_complex_real");
3063     }
3064 }
3065 
3066 /// Initializes all data structures used by the header generator
3067 void initialize()
3068 {
3069     __gshared bool initialized;
3070 
3071     if (!initialized)
3072     {
3073         initialized = true;
3074 
3075         DMDType._init();
3076     }
3077 }
3078 
3079 /// Writes `#if <content>` into the supplied buffer
3080 void hashIf(ref OutBuffer buf, string content)
3081 {
3082     buf.writestring("#if ");
3083     buf.writestringln(content);
3084 }
3085 
3086 /// Writes `#elif <content>` into the supplied buffer
3087 void hashElIf(ref OutBuffer buf, string content)
3088 {
3089     buf.writestring("#elif ");
3090     buf.writestringln(content);
3091 }
3092 
3093 /// Writes `#endif` into the supplied buffer
3094 void hashEndIf(ref OutBuffer buf)
3095 {
3096     buf.writestringln("#endif");
3097 }
3098 
3099 /// Writes `#define <content>` into the supplied buffer
3100 void hashDefine(ref OutBuffer buf, string content)
3101 {
3102     buf.writestring("#define ");
3103     buf.writestringln(content);
3104 }
3105 
3106 /// Writes `#include <content>` into the supplied buffer
3107 void hashInclude(ref OutBuffer buf, string content)
3108 {
3109     buf.writestring("#include ");
3110     buf.writestringln(content);
3111 }
3112 
3113 /// Determines whether `ident` is a reserved keyword in C++
3114 /// Returns: the kind of keyword or `null`
3115 const(char*) keywordClass(const Identifier ident)
3116 {
3117     if (!ident)
3118         return null;
3119 
3120     const name = ident.toString();
3121     switch (name)
3122     {
3123         // C++ operators
3124         case "and":
3125         case "and_eq":
3126         case "bitand":
3127         case "bitor":
3128         case "compl":
3129         case "not":
3130         case "not_eq":
3131         case "or":
3132         case "or_eq":
3133         case "xor":
3134         case "xor_eq":
3135             return "special operator in C++";
3136 
3137         // C++ keywords
3138         case "_Complex":
3139         case "const_cast":
3140         case "delete":
3141         case "dynamic_cast":
3142         case "explicit":
3143         case "friend":
3144         case "inline":
3145         case "mutable":
3146         case "namespace":
3147         case "operator":
3148         case "register":
3149         case "reinterpret_cast":
3150         case "signed":
3151         case "static_cast":
3152         case "typedef":
3153         case "typename":
3154         case "unsigned":
3155         case "using":
3156         case "virtual":
3157         case "volatile":
3158             return "keyword in C++";
3159 
3160         // Common macros imported by this header
3161         // stddef.h
3162         case "offsetof":
3163         case "NULL":
3164             return "default macro in C++";
3165 
3166         // C++11 keywords
3167         case "alignas":
3168         case "alignof":
3169         case "char16_t":
3170         case "char32_t":
3171         case "constexpr":
3172         case "decltype":
3173         case "noexcept":
3174         case "nullptr":
3175         case "static_assert":
3176         case "thread_local":
3177         case "wchar_t":
3178             if (global.params.cplusplus >= CppStdRevision.cpp11)
3179                 return "keyword in C++11";
3180             return null;
3181 
3182         // C++20 keywords
3183         case "char8_t":
3184         case "consteval":
3185         case "constinit":
3186         // Concepts-related keywords
3187         case "concept":
3188         case "requires":
3189         // Coroutines-related keywords
3190         case "co_await":
3191         case "co_yield":
3192         case "co_return":
3193             if (global.params.cplusplus >= CppStdRevision.cpp20)
3194                 return "keyword in C++20";
3195             return null;
3196 
3197         default:
3198             // Identifiers starting with __ are reserved
3199             if (name.length >= 2 && name[0..2] == "__")
3200                 return "reserved identifier in C++";
3201 
3202             return null;
3203     }
3204 }
3205 
3206 /// Finds the outermost symbol if `sym` is nested.
3207 /// Returns `sym` if it appears at module scope
3208 ASTCodegen.Dsymbol outermostSymbol(ASTCodegen.Dsymbol sym)
3209 {
3210     assert(sym);
3211     while (true)
3212     {
3213         auto par = sym.toParent();
3214         if (!par || par.isModule())
3215             return sym;
3216         sym = par;
3217     }
3218 }
3219 
3220 /// Fetches the symbol for user-defined types from the type `t`
3221 /// if `t` is either `TypeClass`, `TypeStruct` or `TypeEnum`
3222 ASTCodegen.Dsymbol symbolFromType(ASTCodegen.Type t)
3223 {
3224     if (auto tc = t.isTypeClass())
3225         return tc.sym;
3226     if (auto ts = t.isTypeStruct())
3227         return ts.sym;
3228     if (auto te = t.isTypeEnum())
3229         return te.sym;
3230     return null;
3231 }
3232 
3233 /**
3234  * Searches `sym` for a member with the given name.
3235  *
3236  * This method usually delegates to `Dsymbol.search` but might also
3237  * manually check the members if the symbol did not receive semantic
3238  * analysis.
3239  *
3240  * Params:
3241  *   sym  = symbol to search
3242  *   name = identifier of the requested symbol
3243  *
3244  * Returns: the symbol or `null` if not found
3245  */
3246 ASTCodegen.Dsymbol findMember(ASTCodegen.Dsymbol sym, Identifier name)
3247 {
3248     if (auto mem = sym.search(Loc.initial, name, ASTCodegen.IgnoreErrors))
3249         return mem;
3250 
3251     // search doesn't work for declarations inside of uninstantiated
3252     // `TemplateDeclaration`s due to the missing symtab.
3253     if (sym.semanticRun >= ASTCodegen.PASS.semanticdone)
3254         return null;
3255 
3256     // Manually check the members if present
3257     auto sds = sym.isScopeDsymbol();
3258     if (!sds || !sds.members)
3259         return null;
3260 
3261     /// Recursively searches for `name` without entering nested aggregates, ...
3262     static ASTCodegen.Dsymbol search(ASTCodegen.Dsymbols* members, Identifier name)
3263     {
3264         foreach (mem; *members)
3265         {
3266             if (mem.ident == name)
3267                 return mem;
3268 
3269             // Look inside of private:, ...
3270             if (auto ad = mem.isAttribDeclaration())
3271             {
3272                 if (auto s = search(ad.decl, name))
3273                     return s;
3274             }
3275         }
3276         return null;
3277     }
3278 
3279     return search(sds.members, name);
3280 }
3281 
3282 debug (Debug_DtoH)
3283 {
3284     /// Generates code to trace the entry and exit of the enclosing `visit` function
3285     string traceVisit(alias node)()
3286     {
3287         const type = typeof(node).stringof;
3288         const method = __traits(hasMember, node, "toPrettyChars") ? "toPrettyChars" : "toChars";
3289         const arg = __traits(identifier, node) ~ '.' ~ method;
3290 
3291         return `printf("[` ~ type ~  ` enter] %s\n", ` ~ arg ~ `());
3292                 scope(exit) printf("[` ~ type ~ ` exit] %s\n", ` ~ arg ~ `());`;
3293     }
3294 }
3295