1 //===- DiagnosticRenderer.cpp - Diagnostic Pretty-Printing ----------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #include "clang/Frontend/DiagnosticRenderer.h"
10 #include "clang/Basic/Diagnostic.h"
11 #include "clang/Basic/DiagnosticOptions.h"
12 #include "clang/Basic/LLVM.h"
13 #include "clang/Basic/SourceLocation.h"
14 #include "clang/Basic/SourceManager.h"
15 #include "clang/Edit/Commit.h"
16 #include "clang/Edit/EditedSource.h"
17 #include "clang/Edit/EditsReceiver.h"
18 #include "clang/Lex/Lexer.h"
19 #include "llvm/ADT/ArrayRef.h"
20 #include "llvm/ADT/DenseMap.h"
21 #include "llvm/ADT/SmallString.h"
22 #include "llvm/ADT/SmallVector.h"
23 #include "llvm/ADT/StringRef.h"
24 #include "llvm/Support/raw_ostream.h"
25 #include <algorithm>
26 #include <cassert>
27 #include <iterator>
28 #include <utility>
29 
30 using namespace clang;
31 
32 DiagnosticRenderer::DiagnosticRenderer(const LangOptions &LangOpts,
33                                        DiagnosticOptions *DiagOpts)
34     : LangOpts(LangOpts), DiagOpts(DiagOpts), LastLevel() {}
35 
36 DiagnosticRenderer::~DiagnosticRenderer() = default;
37 
38 namespace {
39 
40 class FixitReceiver : public edit::EditsReceiver {
41   SmallVectorImpl<FixItHint> &MergedFixits;
42 
43 public:
44   FixitReceiver(SmallVectorImpl<FixItHint> &MergedFixits)
45       : MergedFixits(MergedFixits) {}
46 
47   void insert(SourceLocation loc, StringRef text) override {
48     MergedFixits.push_back(FixItHint::CreateInsertion(loc, text));
49   }
50 
51   void replace(CharSourceRange range, StringRef text) override {
52     MergedFixits.push_back(FixItHint::CreateReplacement(range, text));
53   }
54 };
55 
56 } // namespace
57 
58 static void mergeFixits(ArrayRef<FixItHint> FixItHints,
59                         const SourceManager &SM, const LangOptions &LangOpts,
60                         SmallVectorImpl<FixItHint> &MergedFixits) {
61   edit::Commit commit(SM, LangOpts);
62   for (const auto &Hint : FixItHints)
63     if (Hint.CodeToInsert.empty()) {
64       if (Hint.InsertFromRange.isValid())
65         commit.insertFromRange(Hint.RemoveRange.getBegin(),
66                            Hint.InsertFromRange, /*afterToken=*/false,
67                            Hint.BeforePreviousInsertions);
68       else
69         commit.remove(Hint.RemoveRange);
70     } else {
71       if (Hint.RemoveRange.isTokenRange() ||
72           Hint.RemoveRange.getBegin() != Hint.RemoveRange.getEnd())
73         commit.replace(Hint.RemoveRange, Hint.CodeToInsert);
74       else
75         commit.insert(Hint.RemoveRange.getBegin(), Hint.CodeToInsert,
76                     /*afterToken=*/false, Hint.BeforePreviousInsertions);
77     }
78 
79   edit::EditedSource Editor(SM, LangOpts);
80   if (Editor.commit(commit)) {
81     FixitReceiver Rec(MergedFixits);
82     Editor.applyRewrites(Rec);
83   }
84 }
85 
86 void DiagnosticRenderer::emitDiagnostic(FullSourceLoc Loc,
87                                         DiagnosticsEngine::Level Level,
88                                         StringRef Message,
89                                         ArrayRef<CharSourceRange> Ranges,
90                                         ArrayRef<FixItHint> FixItHints,
91                                         DiagOrStoredDiag D) {
92   assert(Loc.hasManager() || Loc.isInvalid());
93 
94   beginDiagnostic(D, Level);
95 
96   if (!Loc.isValid())
97     // If we have no source location, just emit the diagnostic message.
98     emitDiagnosticMessage(Loc, PresumedLoc(), Level, Message, Ranges, D);
99   else {
100     // Get the ranges into a local array we can hack on.
101     SmallVector<CharSourceRange, 20> MutableRanges(Ranges.begin(),
102                                                    Ranges.end());
103 
104     SmallVector<FixItHint, 8> MergedFixits;
105     if (!FixItHints.empty()) {
106       mergeFixits(FixItHints, Loc.getManager(), LangOpts, MergedFixits);
107       FixItHints = MergedFixits;
108     }
109 
110     for (const auto &Hint : FixItHints)
111       if (Hint.RemoveRange.isValid())
112         MutableRanges.push_back(Hint.RemoveRange);
113 
114     FullSourceLoc UnexpandedLoc = Loc;
115 
116     // Find the ultimate expansion location for the diagnostic.
117     Loc = Loc.getFileLoc();
118 
119     PresumedLoc PLoc = Loc.getPresumedLoc(DiagOpts->ShowPresumedLoc);
120 
121     // First, if this diagnostic is not in the main file, print out the
122     // "included from" lines.
123     emitIncludeStack(Loc, PLoc, Level);
124 
125     // Next, emit the actual diagnostic message and caret.
126     emitDiagnosticMessage(Loc, PLoc, Level, Message, Ranges, D);
127     emitCaret(Loc, Level, MutableRanges, FixItHints);
128 
129     // If this location is within a macro, walk from UnexpandedLoc up to Loc
130     // and produce a macro backtrace.
131     if (UnexpandedLoc.isValid() && UnexpandedLoc.isMacroID()) {
132       emitMacroExpansions(UnexpandedLoc, Level, MutableRanges, FixItHints);
133     }
134   }
135 
136   LastLoc = Loc;
137   LastLevel = Level;
138 
139   endDiagnostic(D, Level);
140 }
141 
142 void DiagnosticRenderer::emitStoredDiagnostic(StoredDiagnostic &Diag) {
143   emitDiagnostic(Diag.getLocation(), Diag.getLevel(), Diag.getMessage(),
144                  Diag.getRanges(), Diag.getFixIts(),
145                  &Diag);
146 }
147 
148 void DiagnosticRenderer::emitBasicNote(StringRef Message) {
149   emitDiagnosticMessage(FullSourceLoc(), PresumedLoc(), DiagnosticsEngine::Note,
150                         Message, std::nullopt, DiagOrStoredDiag());
151 }
152 
153 /// Prints an include stack when appropriate for a particular
154 /// diagnostic level and location.
155 ///
156 /// This routine handles all the logic of suppressing particular include
157 /// stacks (such as those for notes) and duplicate include stacks when
158 /// repeated warnings occur within the same file. It also handles the logic
159 /// of customizing the formatting and display of the include stack.
160 ///
161 /// \param Loc   The diagnostic location.
162 /// \param PLoc  The presumed location of the diagnostic location.
163 /// \param Level The diagnostic level of the message this stack pertains to.
164 void DiagnosticRenderer::emitIncludeStack(FullSourceLoc Loc, PresumedLoc PLoc,
165                                           DiagnosticsEngine::Level Level) {
166   FullSourceLoc IncludeLoc =
167       PLoc.isInvalid() ? FullSourceLoc()
168                        : FullSourceLoc(PLoc.getIncludeLoc(), Loc.getManager());
169 
170   // Skip redundant include stacks altogether.
171   if (LastIncludeLoc == IncludeLoc)
172     return;
173 
174   LastIncludeLoc = IncludeLoc;
175 
176   if (!DiagOpts->ShowNoteIncludeStack && Level == DiagnosticsEngine::Note)
177     return;
178 
179   if (IncludeLoc.isValid())
180     emitIncludeStackRecursively(IncludeLoc);
181   else {
182     emitModuleBuildStack(Loc.getManager());
183     emitImportStack(Loc);
184   }
185 }
186 
187 /// Helper to recursively walk up the include stack and print each layer
188 /// on the way back down.
189 void DiagnosticRenderer::emitIncludeStackRecursively(FullSourceLoc Loc) {
190   if (Loc.isInvalid()) {
191     emitModuleBuildStack(Loc.getManager());
192     return;
193   }
194 
195   PresumedLoc PLoc = Loc.getPresumedLoc(DiagOpts->ShowPresumedLoc);
196   if (PLoc.isInvalid())
197     return;
198 
199   // If this source location was imported from a module, print the module
200   // import stack rather than the
201   // FIXME: We want submodule granularity here.
202   std::pair<FullSourceLoc, StringRef> Imported = Loc.getModuleImportLoc();
203   if (!Imported.second.empty()) {
204     // This location was imported by a module. Emit the module import stack.
205     emitImportStackRecursively(Imported.first, Imported.second);
206     return;
207   }
208 
209   // Emit the other include frames first.
210   emitIncludeStackRecursively(
211       FullSourceLoc(PLoc.getIncludeLoc(), Loc.getManager()));
212 
213   // Emit the inclusion text/note.
214   emitIncludeLocation(Loc, PLoc);
215 }
216 
217 /// Emit the module import stack associated with the current location.
218 void DiagnosticRenderer::emitImportStack(FullSourceLoc Loc) {
219   if (Loc.isInvalid()) {
220     emitModuleBuildStack(Loc.getManager());
221     return;
222   }
223 
224   std::pair<FullSourceLoc, StringRef> NextImportLoc = Loc.getModuleImportLoc();
225   emitImportStackRecursively(NextImportLoc.first, NextImportLoc.second);
226 }
227 
228 /// Helper to recursively walk up the import stack and print each layer
229 /// on the way back down.
230 void DiagnosticRenderer::emitImportStackRecursively(FullSourceLoc Loc,
231                                                     StringRef ModuleName) {
232   if (ModuleName.empty()) {
233     return;
234   }
235 
236   PresumedLoc PLoc = Loc.getPresumedLoc(DiagOpts->ShowPresumedLoc);
237 
238   // Emit the other import frames first.
239   std::pair<FullSourceLoc, StringRef> NextImportLoc = Loc.getModuleImportLoc();
240   emitImportStackRecursively(NextImportLoc.first, NextImportLoc.second);
241 
242   // Emit the inclusion text/note.
243   emitImportLocation(Loc, PLoc, ModuleName);
244 }
245 
246 /// Emit the module build stack, for cases where a module is (re-)built
247 /// on demand.
248 void DiagnosticRenderer::emitModuleBuildStack(const SourceManager &SM) {
249   ModuleBuildStack Stack = SM.getModuleBuildStack();
250   for (const auto &I : Stack) {
251     emitBuildingModuleLocation(I.second, I.second.getPresumedLoc(
252                                               DiagOpts->ShowPresumedLoc),
253                                I.first);
254   }
255 }
256 
257 /// A recursive function to trace all possible backtrace locations
258 /// to match the \p CaretLocFileID.
259 static SourceLocation
260 retrieveMacroLocation(SourceLocation Loc, FileID MacroFileID,
261                       FileID CaretFileID,
262                       const SmallVectorImpl<FileID> &CommonArgExpansions,
263                       bool IsBegin, const SourceManager *SM,
264                       bool &IsTokenRange) {
265   assert(SM->getFileID(Loc) == MacroFileID);
266   if (MacroFileID == CaretFileID)
267     return Loc;
268   if (!Loc.isMacroID())
269     return {};
270 
271   CharSourceRange MacroRange, MacroArgRange;
272 
273   if (SM->isMacroArgExpansion(Loc)) {
274     // Only look at the immediate spelling location of this macro argument if
275     // the other location in the source range is also present in that expansion.
276     if (std::binary_search(CommonArgExpansions.begin(),
277                            CommonArgExpansions.end(), MacroFileID))
278       MacroRange =
279           CharSourceRange(SM->getImmediateSpellingLoc(Loc), IsTokenRange);
280     MacroArgRange = SM->getImmediateExpansionRange(Loc);
281   } else {
282     MacroRange = SM->getImmediateExpansionRange(Loc);
283     MacroArgRange =
284         CharSourceRange(SM->getImmediateSpellingLoc(Loc), IsTokenRange);
285   }
286 
287   SourceLocation MacroLocation =
288       IsBegin ? MacroRange.getBegin() : MacroRange.getEnd();
289   if (MacroLocation.isValid()) {
290     MacroFileID = SM->getFileID(MacroLocation);
291     bool TokenRange = IsBegin ? IsTokenRange : MacroRange.isTokenRange();
292     MacroLocation =
293         retrieveMacroLocation(MacroLocation, MacroFileID, CaretFileID,
294                               CommonArgExpansions, IsBegin, SM, TokenRange);
295     if (MacroLocation.isValid()) {
296       IsTokenRange = TokenRange;
297       return MacroLocation;
298     }
299   }
300 
301   // If we moved the end of the range to an expansion location, we now have
302   // a range of the same kind as the expansion range.
303   if (!IsBegin)
304     IsTokenRange = MacroArgRange.isTokenRange();
305 
306   SourceLocation MacroArgLocation =
307       IsBegin ? MacroArgRange.getBegin() : MacroArgRange.getEnd();
308   MacroFileID = SM->getFileID(MacroArgLocation);
309   return retrieveMacroLocation(MacroArgLocation, MacroFileID, CaretFileID,
310                                CommonArgExpansions, IsBegin, SM, IsTokenRange);
311 }
312 
313 /// Walk up the chain of macro expansions and collect the FileIDs identifying the
314 /// expansions.
315 static void getMacroArgExpansionFileIDs(SourceLocation Loc,
316                                         SmallVectorImpl<FileID> &IDs,
317                                         bool IsBegin, const SourceManager *SM) {
318   while (Loc.isMacroID()) {
319     if (SM->isMacroArgExpansion(Loc)) {
320       IDs.push_back(SM->getFileID(Loc));
321       Loc = SM->getImmediateSpellingLoc(Loc);
322     } else {
323       auto ExpRange = SM->getImmediateExpansionRange(Loc);
324       Loc = IsBegin ? ExpRange.getBegin() : ExpRange.getEnd();
325     }
326   }
327 }
328 
329 /// Collect the expansions of the begin and end locations and compute the set
330 /// intersection. Produces a sorted vector of FileIDs in CommonArgExpansions.
331 static void computeCommonMacroArgExpansionFileIDs(
332     SourceLocation Begin, SourceLocation End, const SourceManager *SM,
333     SmallVectorImpl<FileID> &CommonArgExpansions) {
334   SmallVector<FileID, 4> BeginArgExpansions;
335   SmallVector<FileID, 4> EndArgExpansions;
336   getMacroArgExpansionFileIDs(Begin, BeginArgExpansions, /*IsBegin=*/true, SM);
337   getMacroArgExpansionFileIDs(End, EndArgExpansions, /*IsBegin=*/false, SM);
338   llvm::sort(BeginArgExpansions);
339   llvm::sort(EndArgExpansions);
340   std::set_intersection(BeginArgExpansions.begin(), BeginArgExpansions.end(),
341                         EndArgExpansions.begin(), EndArgExpansions.end(),
342                         std::back_inserter(CommonArgExpansions));
343 }
344 
345 // Helper function to fix up source ranges.  It takes in an array of ranges,
346 // and outputs an array of ranges where we want to draw the range highlighting
347 // around the location specified by CaretLoc.
348 //
349 // To find locations which correspond to the caret, we crawl the macro caller
350 // chain for the beginning and end of each range.  If the caret location
351 // is in a macro expansion, we search each chain for a location
352 // in the same expansion as the caret; otherwise, we crawl to the top of
353 // each chain. Two locations are part of the same macro expansion
354 // iff the FileID is the same.
355 static void
356 mapDiagnosticRanges(FullSourceLoc CaretLoc, ArrayRef<CharSourceRange> Ranges,
357                     SmallVectorImpl<CharSourceRange> &SpellingRanges) {
358   FileID CaretLocFileID = CaretLoc.getFileID();
359 
360   const SourceManager *SM = &CaretLoc.getManager();
361 
362   for (const auto &Range : Ranges) {
363     if (Range.isInvalid())
364       continue;
365 
366     SourceLocation Begin = Range.getBegin(), End = Range.getEnd();
367     bool IsTokenRange = Range.isTokenRange();
368 
369     FileID BeginFileID = SM->getFileID(Begin);
370     FileID EndFileID = SM->getFileID(End);
371 
372     // Find the common parent for the beginning and end of the range.
373 
374     // First, crawl the expansion chain for the beginning of the range.
375     llvm::SmallDenseMap<FileID, SourceLocation> BeginLocsMap;
376     while (Begin.isMacroID() && BeginFileID != EndFileID) {
377       BeginLocsMap[BeginFileID] = Begin;
378       Begin = SM->getImmediateExpansionRange(Begin).getBegin();
379       BeginFileID = SM->getFileID(Begin);
380     }
381 
382     // Then, crawl the expansion chain for the end of the range.
383     if (BeginFileID != EndFileID) {
384       while (End.isMacroID() && !BeginLocsMap.count(EndFileID)) {
385         auto Exp = SM->getImmediateExpansionRange(End);
386         IsTokenRange = Exp.isTokenRange();
387         End = Exp.getEnd();
388         EndFileID = SM->getFileID(End);
389       }
390       if (End.isMacroID()) {
391         Begin = BeginLocsMap[EndFileID];
392         BeginFileID = EndFileID;
393       }
394     }
395 
396     // There is a chance that begin or end is invalid here, for example if
397     // specific compile error is reported.
398     // It is possible that the FileID's do not match, if one comes from an
399     // included file. In this case we can not produce a meaningful source range.
400     if (Begin.isInvalid() || End.isInvalid() || BeginFileID != EndFileID)
401       continue;
402 
403     // Do the backtracking.
404     SmallVector<FileID, 4> CommonArgExpansions;
405     computeCommonMacroArgExpansionFileIDs(Begin, End, SM, CommonArgExpansions);
406     Begin = retrieveMacroLocation(Begin, BeginFileID, CaretLocFileID,
407                                   CommonArgExpansions, /*IsBegin=*/true, SM,
408                                   IsTokenRange);
409     End = retrieveMacroLocation(End, BeginFileID, CaretLocFileID,
410                                 CommonArgExpansions, /*IsBegin=*/false, SM,
411                                 IsTokenRange);
412     if (Begin.isInvalid() || End.isInvalid()) continue;
413 
414     // Return the spelling location of the beginning and end of the range.
415     Begin = SM->getSpellingLoc(Begin);
416     End = SM->getSpellingLoc(End);
417 
418     SpellingRanges.push_back(CharSourceRange(SourceRange(Begin, End),
419                                              IsTokenRange));
420   }
421 }
422 
423 void DiagnosticRenderer::emitCaret(FullSourceLoc Loc,
424                                    DiagnosticsEngine::Level Level,
425                                    ArrayRef<CharSourceRange> Ranges,
426                                    ArrayRef<FixItHint> Hints) {
427   SmallVector<CharSourceRange, 4> SpellingRanges;
428   mapDiagnosticRanges(Loc, Ranges, SpellingRanges);
429   emitCodeContext(Loc, Level, SpellingRanges, Hints);
430 }
431 
432 /// A helper function for emitMacroExpansion to print the
433 /// macro expansion message
434 void DiagnosticRenderer::emitSingleMacroExpansion(
435     FullSourceLoc Loc, DiagnosticsEngine::Level Level,
436     ArrayRef<CharSourceRange> Ranges) {
437   // Find the spelling location for the macro definition. We must use the
438   // spelling location here to avoid emitting a macro backtrace for the note.
439   FullSourceLoc SpellingLoc = Loc.getSpellingLoc();
440 
441   // Map the ranges into the FileID of the diagnostic location.
442   SmallVector<CharSourceRange, 4> SpellingRanges;
443   mapDiagnosticRanges(Loc, Ranges, SpellingRanges);
444 
445   SmallString<100> MessageStorage;
446   llvm::raw_svector_ostream Message(MessageStorage);
447   StringRef MacroName = Lexer::getImmediateMacroNameForDiagnostics(
448       Loc, Loc.getManager(), LangOpts);
449   if (MacroName.empty())
450     Message << "expanded from here";
451   else
452     Message << "expanded from macro '" << MacroName << "'";
453 
454   emitDiagnostic(SpellingLoc, DiagnosticsEngine::Note, Message.str(),
455                  SpellingRanges, std::nullopt);
456 }
457 
458 /// Check that the macro argument location of Loc starts with ArgumentLoc.
459 /// The starting location of the macro expansions is used to differeniate
460 /// different macro expansions.
461 static bool checkLocForMacroArgExpansion(SourceLocation Loc,
462                                          const SourceManager &SM,
463                                          SourceLocation ArgumentLoc) {
464   SourceLocation MacroLoc;
465   if (SM.isMacroArgExpansion(Loc, &MacroLoc)) {
466     if (ArgumentLoc == MacroLoc) return true;
467   }
468 
469   return false;
470 }
471 
472 /// Check if all the locations in the range have the same macro argument
473 /// expansion, and that the expansion starts with ArgumentLoc.
474 static bool checkRangeForMacroArgExpansion(CharSourceRange Range,
475                                            const SourceManager &SM,
476                                            SourceLocation ArgumentLoc) {
477   SourceLocation BegLoc = Range.getBegin(), EndLoc = Range.getEnd();
478   while (BegLoc != EndLoc) {
479     if (!checkLocForMacroArgExpansion(BegLoc, SM, ArgumentLoc))
480       return false;
481     BegLoc.getLocWithOffset(1);
482   }
483 
484   return checkLocForMacroArgExpansion(BegLoc, SM, ArgumentLoc);
485 }
486 
487 /// A helper function to check if the current ranges are all inside the same
488 /// macro argument expansion as Loc.
489 static bool checkRangesForMacroArgExpansion(FullSourceLoc Loc,
490                                             ArrayRef<CharSourceRange> Ranges) {
491   assert(Loc.isMacroID() && "Must be a macro expansion!");
492 
493   SmallVector<CharSourceRange, 4> SpellingRanges;
494   mapDiagnosticRanges(Loc, Ranges, SpellingRanges);
495 
496   /// Count all valid ranges.
497   unsigned ValidCount = 0;
498   for (const auto &Range : Ranges)
499     if (Range.isValid())
500       ValidCount++;
501 
502   if (ValidCount > SpellingRanges.size())
503     return false;
504 
505   /// To store the source location of the argument location.
506   FullSourceLoc ArgumentLoc;
507 
508   /// Set the ArgumentLoc to the beginning location of the expansion of Loc
509   /// so to check if the ranges expands to the same beginning location.
510   if (!Loc.isMacroArgExpansion(&ArgumentLoc))
511     return false;
512 
513   for (const auto &Range : SpellingRanges)
514     if (!checkRangeForMacroArgExpansion(Range, Loc.getManager(), ArgumentLoc))
515       return false;
516 
517   return true;
518 }
519 
520 /// Recursively emit notes for each macro expansion and caret
521 /// diagnostics where appropriate.
522 ///
523 /// Walks up the macro expansion stack printing expansion notes, the code
524 /// snippet, caret, underlines and FixItHint display as appropriate at each
525 /// level.
526 ///
527 /// \param Loc The location for this caret.
528 /// \param Level The diagnostic level currently being emitted.
529 /// \param Ranges The underlined ranges for this code snippet.
530 /// \param Hints The FixIt hints active for this diagnostic.
531 void DiagnosticRenderer::emitMacroExpansions(FullSourceLoc Loc,
532                                              DiagnosticsEngine::Level Level,
533                                              ArrayRef<CharSourceRange> Ranges,
534                                              ArrayRef<FixItHint> Hints) {
535   assert(Loc.isValid() && "must have a valid source location here");
536   const SourceManager &SM = Loc.getManager();
537   SourceLocation L = Loc;
538 
539   // Produce a stack of macro backtraces.
540   SmallVector<SourceLocation, 8> LocationStack;
541   unsigned IgnoredEnd = 0;
542   while (L.isMacroID()) {
543     // If this is the expansion of a macro argument, point the caret at the
544     // use of the argument in the definition of the macro, not the expansion.
545     if (SM.isMacroArgExpansion(L))
546       LocationStack.push_back(SM.getImmediateExpansionRange(L).getBegin());
547     else
548       LocationStack.push_back(L);
549 
550     if (checkRangesForMacroArgExpansion(FullSourceLoc(L, SM), Ranges))
551       IgnoredEnd = LocationStack.size();
552 
553     L = SM.getImmediateMacroCallerLoc(L);
554 
555     // Once the location no longer points into a macro, try stepping through
556     // the last found location.  This sometimes produces additional useful
557     // backtraces.
558     if (L.isFileID())
559       L = SM.getImmediateMacroCallerLoc(LocationStack.back());
560     assert(L.isValid() && "must have a valid source location here");
561   }
562 
563   LocationStack.erase(LocationStack.begin(),
564                       LocationStack.begin() + IgnoredEnd);
565 
566   unsigned MacroDepth = LocationStack.size();
567   unsigned MacroLimit = DiagOpts->MacroBacktraceLimit;
568   if (MacroDepth <= MacroLimit || MacroLimit == 0) {
569     for (auto I = LocationStack.rbegin(), E = LocationStack.rend();
570          I != E; ++I)
571       emitSingleMacroExpansion(FullSourceLoc(*I, SM), Level, Ranges);
572     return;
573   }
574 
575   unsigned MacroStartMessages = MacroLimit / 2;
576   unsigned MacroEndMessages = MacroLimit / 2 + MacroLimit % 2;
577 
578   for (auto I = LocationStack.rbegin(),
579             E = LocationStack.rbegin() + MacroStartMessages;
580        I != E; ++I)
581     emitSingleMacroExpansion(FullSourceLoc(*I, SM), Level, Ranges);
582 
583   SmallString<200> MessageStorage;
584   llvm::raw_svector_ostream Message(MessageStorage);
585   Message << "(skipping " << (MacroDepth - MacroLimit)
586           << " expansions in backtrace; use -fmacro-backtrace-limit=0 to "
587              "see all)";
588   emitBasicNote(Message.str());
589 
590   for (auto I = LocationStack.rend() - MacroEndMessages,
591             E = LocationStack.rend();
592        I != E; ++I)
593     emitSingleMacroExpansion(FullSourceLoc(*I, SM), Level, Ranges);
594 }
595 
596 DiagnosticNoteRenderer::~DiagnosticNoteRenderer() = default;
597 
598 void DiagnosticNoteRenderer::emitIncludeLocation(FullSourceLoc Loc,
599                                                  PresumedLoc PLoc) {
600   // Generate a note indicating the include location.
601   SmallString<200> MessageStorage;
602   llvm::raw_svector_ostream Message(MessageStorage);
603   Message << "in file included from " << PLoc.getFilename() << ':'
604           << PLoc.getLine() << ":";
605   emitNote(Loc, Message.str());
606 }
607 
608 void DiagnosticNoteRenderer::emitImportLocation(FullSourceLoc Loc,
609                                                 PresumedLoc PLoc,
610                                                 StringRef ModuleName) {
611   // Generate a note indicating the include location.
612   SmallString<200> MessageStorage;
613   llvm::raw_svector_ostream Message(MessageStorage);
614   Message << "in module '" << ModuleName;
615   if (PLoc.isValid())
616     Message << "' imported from " << PLoc.getFilename() << ':'
617             << PLoc.getLine();
618   Message << ":";
619   emitNote(Loc, Message.str());
620 }
621 
622 void DiagnosticNoteRenderer::emitBuildingModuleLocation(FullSourceLoc Loc,
623                                                         PresumedLoc PLoc,
624                                                         StringRef ModuleName) {
625   // Generate a note indicating the include location.
626   SmallString<200> MessageStorage;
627   llvm::raw_svector_ostream Message(MessageStorage);
628   if (PLoc.isValid())
629     Message << "while building module '" << ModuleName << "' imported from "
630             << PLoc.getFilename() << ':' << PLoc.getLine() << ":";
631   else
632     Message << "while building module '" << ModuleName << "':";
633   emitNote(Loc, Message.str());
634 }
635