1------------------------------------------------------------------------------ 2-- -- 3-- GNAT COMPILER COMPONENTS -- 4-- -- 5-- S E M -- 6-- -- 7-- S p e c -- 8-- -- 9-- Copyright (C) 1992-2019, Free Software Foundation, Inc. -- 10-- -- 11-- GNAT is free software; you can redistribute it and/or modify it under -- 12-- terms of the GNU General Public License as published by the Free Soft- -- 13-- ware Foundation; either version 3, or (at your option) any later ver- -- 14-- sion. GNAT is distributed in the hope that it will be useful, but WITH- -- 15-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY -- 16-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License -- 17-- for more details. You should have received a copy of the GNU General -- 18-- Public License distributed with GNAT; see file COPYING3. If not, go to -- 19-- http://www.gnu.org/licenses for a complete copy of the license. -- 20-- -- 21-- GNAT was originally developed by the GNAT team at New York University. -- 22-- Extensive contributions were provided by Ada Core Technologies Inc. -- 23-- -- 24------------------------------------------------------------------------------ 25 26-------------------------------------- 27-- Semantic Analysis: General Model -- 28-------------------------------------- 29 30-- Semantic processing involves 3 phases which are highly intertwined 31-- (i.e. mutually recursive): 32 33-- Analysis implements the bulk of semantic analysis such as 34-- name analysis and type resolution for declarations, 35-- instructions and expressions. The main routine 36-- driving this process is procedure Analyze given below. 37-- This analysis phase is really a bottom up pass that is 38-- achieved during the recursive traversal performed by the 39-- Analyze_... procedures implemented in the sem_* packages. 40-- For expressions this phase determines unambiguous types 41-- and collects sets of possible types where the 42-- interpretation is potentially ambiguous. 43 44-- Resolution is carried out only for expressions to finish type 45-- resolution that was initiated but not necessarily 46-- completed during analysis (because of overloading 47-- ambiguities). Specifically, after completing the bottom 48-- up pass carried out during analysis for expressions, the 49-- Resolve routine (see the spec of sem_res for more info) 50-- is called to perform a top down resolution with 51-- recursive calls to itself to resolve operands. 52 53-- Expansion if we are not generating code this phase is a no-op. 54-- otherwise this phase expands, i.e. transforms, original 55-- declaration, expressions or instructions into simpler 56-- structures that can be handled by the back-end. This 57-- phase is also in charge of generating code which is 58-- implicit in the original source (for instance for 59-- default initializations, controlled types, etc.) 60-- There are two separate instances where expansion is 61-- invoked. For declarations and instructions, expansion is 62-- invoked just after analysis since no resolution needs 63-- to be performed. For expressions, expansion is done just 64-- after resolution. In both cases expansion is done from the 65-- bottom up just before the end of Analyze for instructions 66-- and declarations or the call to Resolve for expressions. 67-- The main routine driving expansion is Expand. 68-- See the spec of Expander for more details. 69 70-- To summarize, in normal code generation mode we recursively traverse the 71-- abstract syntax tree top-down performing semantic analysis bottom 72-- up. For instructions and declarations, before the call to the Analyze 73-- routine completes we perform expansion since at that point we have all 74-- semantic information needed. For expression nodes, after the call to 75-- Analysis terminates we invoke the Resolve routine to transmit top-down 76-- the type that was gathered by Analyze which will resolve possible 77-- ambiguities in the expression. Just before the call to Resolve 78-- terminates, the expression can be expanded since all the semantic 79-- information is available at that point. 80 81-- If we are not generating code then the expansion phase is a no-op 82 83-- When generating code there are a number of exceptions to the basic 84-- Analysis-Resolution-Expansion model for expressions. The most prominent 85-- examples are the handling of default expressions and aggregates. 86 87----------------------------------------------------------------------- 88-- Handling of Default and Per-Object Expressions (Spec-Expressions) -- 89----------------------------------------------------------------------- 90 91-- The default expressions in component declarations and in procedure 92-- specifications (but not the ones in object declarations) are quite tricky 93-- to handle. The problem is that some processing is required at the point 94-- where the expression appears: 95 96-- visibility analysis (including user defined operators) 97-- freezing of static expressions 98 99-- but other processing must be deferred until the enclosing entity (record or 100-- procedure specification) is frozen: 101 102-- freezing of any other types in the expression expansion 103-- generation of code 104 105-- A similar situation occurs with the argument of priority and interrupt 106-- priority pragmas that appear in task and protected definition specs and 107-- other cases of per-object expressions (see RM 3.8(18)). 108 109-- Another similar case is the conditions in precondition and postcondition 110-- pragmas that appear with subprogram specifications rather than in the body. 111 112-- Collectively we call these Spec_Expressions. The routine that performs the 113-- special analysis is called Analyze_Spec_Expression. 114 115-- Expansion has to be deferred since you can't generate code for expressions 116-- that reference types that have not been frozen yet. As an example, consider 117-- the following: 118 119-- type x is delta 0.5 range -10.0 .. +10.0; 120-- ... 121-- type q is record 122-- xx : x := y * z; 123-- end record; 124 125-- for x'small use 0.25; 126 127-- The expander is in charge of dealing with fixed-point, and of course the 128-- small declaration, which is not too late, since the declaration of type q 129-- does *not* freeze type x, definitely affects the expanded code. 130 131-- Another reason that we cannot expand early is that expansion can generate 132-- range checks. These range checks need to be inserted not at the point of 133-- definition but at the point of use. The whole point here is that the value 134-- of the expression cannot be obtained at the point of declaration, only at 135-- the point of use. 136 137-- Generally our model is to combine analysis resolution and expansion, but 138-- this is the one case where this model falls down. Here is how we patch 139-- it up without causing too much distortion to our basic model. 140 141-- A switch (In_Spec_Expression) is set to show that we are in the initial 142-- occurrence of a default expression. The analyzer is then called on this 143-- expression with the switch set true. Analysis and resolution proceed almost 144-- as usual, except that Freeze_Expression will not freeze non-static 145-- expressions if this switch is set, and the call to Expand at the end of 146-- resolution is skipped. This also skips the code that normally sets the 147-- Analyzed flag to True. The result is that when we are done the tree is 148-- still marked as unanalyzed, but all types for static expressions are frozen 149-- as required, and all entities of variables have been recorded. We then turn 150-- off the switch, and later on reanalyze the expression with the switch off. 151-- The effect is that this second analysis freezes the rest of the types as 152-- required, and generates code but visibility analysis is not repeated since 153-- all the entities are marked. 154 155-- The second analysis (the one that generates code) is in the context 156-- where the code is required. For a record field default, this is in the 157-- initialization procedure for the record and for a subprogram default 158-- parameter, it is at the point the subprogram is frozen. For a priority or 159-- storage size pragma it is in the context of the Init_Proc for the task or 160-- protected object. For a pre/postcondition pragma it is in the body when 161-- code for the pragma is generated. 162 163------------------ 164-- Preanalysis -- 165------------------ 166 167-- For certain kind of expressions, such as aggregates, we need to defer 168-- expansion of the aggregate and its inner expressions until after the whole 169-- set of expressions appearing inside the aggregate have been analyzed. 170-- Consider, for instance the following example: 171-- 172-- (1 .. 100 => new Thing (Function_Call)) 173-- 174-- The normal Analysis-Resolution-Expansion mechanism where expansion of the 175-- children is performed before expansion of the parent does not work if the 176-- code generated for the children by the expander needs to be evaluated 177-- repeatedly (for instance in the above aggregate "new Thing (Function_Call)" 178-- needs to be called 100 times.) 179 180-- The reason this mechanism does not work is that the expanded code for the 181-- children is typically inserted above the parent and thus when the father 182-- gets expanded no re-evaluation takes place. For instance in the case of 183-- aggregates if "new Thing (Function_Call)" is expanded before the aggregate 184-- the expanded code will be placed outside of the aggregate and when 185-- expanding the aggregate the loop from 1 to 100 will not surround the 186-- expanded code for "new Thing (Function_Call)". 187 188-- To remedy this situation we introduce a flag that signals whether we want a 189-- full analysis (i.e. expansion is enabled) or a preanalysis which performs 190-- Analysis and Resolution but no expansion. 191 192-- After the complete preanalysis of an expression has been carried out we 193-- can transform the expression and then carry out the full three stage 194-- (Analyze-Resolve-Expand) cycle on the transformed expression top-down so 195-- that the expansion of inner expressions happens inside the newly generated 196-- node for the parent expression. 197 198-- Note that the difference between processing of default expressions and 199-- preanalysis of other expressions is that we do carry out freezing in 200-- the latter but not in the former (except for static scalar expressions). 201-- The routine that performs preanalysis and corresponding resolution is 202-- called Preanalyze_And_Resolve and is in Sem_Res. 203 204with Alloc; 205with Einfo; use Einfo; 206with Opt; use Opt; 207with Table; 208with Types; use Types; 209 210package Sem is 211 212 ----------------------------- 213 -- Semantic Analysis Flags -- 214 ----------------------------- 215 216 Full_Analysis : Boolean := True; 217 -- Switch to indicate if we are doing a full analysis or a preanalysis. 218 -- In normal analysis mode (Analysis-Expansion for instructions or 219 -- declarations) or (Analysis-Resolution-Expansion for expressions) this 220 -- flag is set. Note that if we are not generating code the expansion phase 221 -- merely sets the Analyzed flag to True in this case. If we are in 222 -- Preanalysis mode (see above) this flag is set to False then the 223 -- expansion phase is skipped. 224 -- 225 -- When this flag is False the flag Expander_Active is also False (the 226 -- Expander_Active flag defined in the spec of package Expander tells you 227 -- whether expansion is currently enabled). You should really regard this 228 -- as a read only flag. 229 230 In_Spec_Expression : Boolean := False; 231 -- Switch to indicate that we are in a spec-expression, as described 232 -- above. Note that this must be recursively saved on a Semantics call 233 -- since it is possible for the analysis of an expression to result in a 234 -- recursive call (e.g. to get the entity for System.Address as part of the 235 -- processing of an Address attribute reference). When this switch is True 236 -- then Full_Analysis above must be False. You should really regard this as 237 -- a read only flag. 238 239 In_Deleted_Code : Boolean := False; 240 -- If the condition in an if-statement is statically known, the branch 241 -- that is not taken is analyzed with expansion disabled, and the tree 242 -- is deleted after analysis. Itypes generated in deleted code must be 243 -- frozen from start, because the tree on which they depend will not 244 -- be available at the freeze point. 245 246 In_Assertion_Expr : Nat := 0; 247 -- This is set non-zero if we are within the expression of an assertion 248 -- pragma or aspect. It is a counter which is incremented at the start of 249 -- expanding such an expression, and decremented on completion of expanding 250 -- that expression. Probably a boolean would be good enough, since we think 251 -- that such expressions cannot nest, but that might not be true in the 252 -- future (e.g. if let expressions are added to Ada) so we prepare for that 253 -- future possibility by making it a counter. As with In_Spec_Expression, 254 -- it must be recursively saved and restored for a Semantics call. 255 256 In_Compile_Time_Warning_Or_Error : Boolean := False; 257 -- Switch to indicate that we are validating a pragma Compile_Time_Warning 258 -- or Compile_Time_Error after the back end has been called (to check these 259 -- pragmas for size and alignment appropriateness). 260 261 In_Default_Expr : Boolean := False; 262 -- Switch to indicate that we are analyzing a default component expression. 263 -- As with In_Spec_Expression, it must be recursively saved and restored 264 -- for a Semantics call. 265 266 In_Inlined_Body : Boolean := False; 267 -- Switch to indicate that we are analyzing and resolving an inlined body. 268 -- Type checking is disabled in this context, because types are known to be 269 -- compatible. This avoids problems with private types whose full view is 270 -- derived from private types. 271 272 Inside_A_Generic : Boolean := False; 273 -- This flag is set if we are processing a generic specification, generic 274 -- definition, or generic body. When this flag is True the Expander_Active 275 -- flag is False to disable any code expansion (see package Expander). Only 276 -- the generic processing can modify the status of this flag, any other 277 -- client should regard it as read-only. 278 -- Probably should be called Inside_A_Generic_Template ??? 279 280 Inside_Freezing_Actions : Nat := 0; 281 -- Flag indicating whether we are within a call to Expand_N_Freeze_Actions. 282 -- Non-zero means we are inside (it is actually a level counter to deal 283 -- with nested calls). Used to avoid traversing the tree each time a 284 -- subprogram call is processed to know if we must not clear all constant 285 -- indications from entities in the current scope. Only the expansion of 286 -- freezing nodes can modify the status of this flag, any other client 287 -- should regard it as read-only. 288 289 Inside_Preanalysis_Without_Freezing : Nat := 0; 290 -- Flag indicating whether we are preanalyzing an expression performing no 291 -- freezing. Non-zero means we are inside (it is actually a level counter 292 -- to deal with nested calls). 293 294 Unloaded_Subunits : Boolean := False; 295 -- This flag is set True if we have subunits that are not loaded. This 296 -- occurs when the main unit is a subunit, and contains lower level 297 -- subunits that are not loaded. We use this flag to suppress warnings 298 -- about unused variables, since these warnings are unreliable in this 299 -- case. We could perhaps do a more accurate job and retain some of the 300 -- warnings, but it is quite a tricky job. 301 302 ----------------------------------- 303 -- Handling of Check Suppression -- 304 ----------------------------------- 305 306 -- There are two kinds of suppress checks: scope based suppress checks, 307 -- and entity based suppress checks. 308 309 -- Scope based suppress checks for the predefined checks (from initial 310 -- command line arguments, or from Suppress pragmas not including an entity 311 -- name) are recorded in the Sem.Scope_Suppress variable, and all that 312 -- is necessary is to save the state of this variable on scope entry, and 313 -- restore it on scope exit. This mechanism allows for fast checking of the 314 -- scope suppress state without needing complex data structures. 315 316 -- Entity based checks, from Suppress/Unsuppress pragmas giving an 317 -- Entity_Id and scope based checks for non-predefined checks (introduced 318 -- using pragma Check_Name), are handled as follows. If a suppress or 319 -- unsuppress pragma is encountered for a given entity, then the flag 320 -- Checks_May_Be_Suppressed is set in the entity and an entry is made in 321 -- either the Local_Entity_Suppress stack (case of pragma that appears in 322 -- other than a package spec), or in the Global_Entity_Suppress stack (case 323 -- of pragma that appears in a package spec, which is by the rule of RM 324 -- 11.5(7) applicable throughout the life of the entity). Similarly, a 325 -- Suppress/Unsuppress pragma for a non-predefined check which does not 326 -- specify an entity is also stored in one of these stacks. 327 328 -- If the Checks_May_Be_Suppressed flag is set in an entity then the 329 -- procedure is to search first the local and then the global suppress 330 -- stacks (we search these in reverse order, top element first). The only 331 -- other point is that we have to make sure that we have proper nested 332 -- interaction between such specific pragmas and locally applied general 333 -- pragmas applying to all entities. This is achieved by including in the 334 -- Local_Entity_Suppress table dummy entries with an empty Entity field 335 -- that are applicable to all entities. A similar search is needed for any 336 -- non-predefined check even if no specific entity is involved. 337 338 Scope_Suppress : Suppress_Record; 339 -- This variable contains the current scope based settings of the suppress 340 -- switches. It is initialized from Suppress_Options in Gnat1drv, and then 341 -- modified by pragma Suppress. On entry to each scope, the current setting 342 -- is saved on the scope stack, and then restored on exit from the scope. 343 -- This record may be rapidly checked to determine the current status of 344 -- a check if no specific entity is involved or if the specific entity 345 -- involved is one for which no specific Suppress/Unsuppress pragma has 346 -- been set (as indicated by the Checks_May_Be_Suppressed flag being set). 347 348 -- This scheme is a little complex, but serves the purpose of enabling 349 -- a very rapid check in the common case where no entity specific pragma 350 -- applies, and gives the right result when such pragmas are used even 351 -- in complex cases of nested Suppress and Unsuppress pragmas. 352 353 -- The Local_Entity_Suppress and Global_Entity_Suppress stacks are handled 354 -- using dynamic allocation and linked lists. We do not often use this 355 -- approach in the compiler (preferring to use extensible tables instead). 356 -- The reason we do it here is that scope stack entries save a pointer to 357 -- the current local stack top, which is also saved and restored on scope 358 -- exit. Furthermore for processing of generics we save pointers to the 359 -- top of the stack, so that the local stack is actually a tree of stacks 360 -- rather than a single stack, a structure that is easy to represent using 361 -- linked lists, but impossible to represent using a single table. Note 362 -- that because of the generic issue, we never release entries in these 363 -- stacks, but that's no big deal, since we are unlikely to have a huge 364 -- number of Suppress/Unsuppress entries in a single compilation. 365 366 type Suppress_Stack_Entry; 367 type Suppress_Stack_Entry_Ptr is access all Suppress_Stack_Entry; 368 369 type Suppress_Stack_Entry is record 370 Entity : Entity_Id; 371 -- Entity to which the check applies, or Empty for a check that has 372 -- no entity name (and thus applies to all entities). 373 374 Check : Check_Id; 375 -- Check which is set (can be All_Checks for the All_Checks case) 376 377 Suppress : Boolean; 378 -- Set True for Suppress, and False for Unsuppress 379 380 Prev : Suppress_Stack_Entry_Ptr; 381 -- Pointer to previous entry on stack 382 383 Next : Suppress_Stack_Entry_Ptr; 384 -- All allocated Suppress_Stack_Entry records are chained together in 385 -- a linked list whose head is Suppress_Stack_Entries, and the Next 386 -- field is used as a forward pointer (null ends the list). This is 387 -- used to free all entries in Sem.Init (which will be important if 388 -- we ever setup the compiler to be reused). 389 end record; 390 391 Suppress_Stack_Entries : Suppress_Stack_Entry_Ptr := null; 392 -- Pointer to linked list of records (see comments for Next above) 393 394 Local_Suppress_Stack_Top : Suppress_Stack_Entry_Ptr; 395 -- Pointer to top element of local suppress stack. This is the entry that 396 -- is saved and restored in the scope stack, and also saved for generic 397 -- body expansion. 398 399 Global_Suppress_Stack_Top : Suppress_Stack_Entry_Ptr; 400 -- Pointer to top element of global suppress stack 401 402 procedure Push_Local_Suppress_Stack_Entry 403 (Entity : Entity_Id; 404 Check : Check_Id; 405 Suppress : Boolean); 406 -- Push a new entry on to the top of the local suppress stack, updating 407 -- the value in Local_Suppress_Stack_Top; 408 409 procedure Push_Global_Suppress_Stack_Entry 410 (Entity : Entity_Id; 411 Check : Check_Id; 412 Suppress : Boolean); 413 -- Push a new entry on to the top of the global suppress stack, updating 414 -- the value in Global_Suppress_Stack_Top; 415 416 ----------------- 417 -- Scope Stack -- 418 ----------------- 419 420 -- The scope stack indicates the declarative regions that are currently 421 -- being processed (analyzed and/or expanded). The scope stack is one of 422 -- the basic visibility structures in the compiler: entities that are 423 -- declared in a scope that is currently on the scope stack are immediately 424 -- visible (leaving aside issues of hiding and overloading). 425 426 -- Initially, the scope stack only contains an entry for package Standard. 427 -- When a compilation unit, subprogram unit, block or declarative region 428 -- is being processed, the corresponding entity is pushed on the scope 429 -- stack. It is removed after the processing step is completed. A given 430 -- entity can be placed several times on the scope stack, for example 431 -- when processing derived type declarations, freeze nodes, etc. The top 432 -- of the scope stack is the innermost scope currently being processed. 433 -- It is obtained through function Current_Scope. After a compilation unit 434 -- has been processed, the scope stack must contain only Standard. 435 -- The predicate In_Open_Scopes specifies whether a scope is currently 436 -- on the scope stack. 437 438 -- This model is complicated by the need to compile units on the fly, in 439 -- the middle of the compilation of other units. This arises when compiling 440 -- instantiations, and when compiling run-time packages obtained through 441 -- rtsfind. Given that the scope stack is a single static and global 442 -- structure (not originally designed for the recursive processing required 443 -- by rtsfind for example) additional machinery is needed to indicate what 444 -- is currently being compiled. As a result, the scope stack holds several 445 -- contiguous sections that correspond to the compilation of a given 446 -- compilation unit. These sections are separated by distinct occurrences 447 -- of package Standard. The currently active section of the scope stack 448 -- goes from the current scope to the first (innermost) occurrence of 449 -- Standard, which is additionally marked with flag Is_Active_Stack_Base. 450 -- The basic visibility routine (Find_Direct_Name, in Sem_Ch8) uses this 451 -- contiguous section of the scope stack to determine whether a given 452 -- entity is or is not visible at a point. In_Open_Scopes only examines 453 -- the currently active section of the scope stack. 454 455 -- Similar complications arise when processing child instances. These 456 -- must be compiled in the context of parent instances, and therefore the 457 -- parents must be pushed on the stack before compiling the child, and 458 -- removed afterwards. Routines Save_Scope_Stack and Restore_Scope_Stack 459 -- are used to set/reset the visibility of entities declared in scopes 460 -- that are currently on the scope stack, and are used when compiling 461 -- instance bodies on the fly. 462 463 -- It is clear in retrospect that all semantic processing and visibility 464 -- structures should have been fully recursive. The rtsfind mechanism, 465 -- and the complexities brought about by subunits and by generic child 466 -- units and their instantiations, have led to a hybrid model that carries 467 -- more state than one would wish. 468 469 type Scope_Action_Kind is (Before, After, Cleanup); 470 type Scope_Actions is array (Scope_Action_Kind) of List_Id; 471 -- Transient blocks have three associated actions list, to be inserted 472 -- before and after the block's statements, and as cleanup actions. 473 474 Configuration_Component_Alignment : Component_Alignment_Kind := 475 Calign_Default; 476 -- Used for handling the pragma Component_Alignment in the context of a 477 -- configuration file. 478 479 type Scope_Stack_Entry is record 480 Entity : Entity_Id; 481 -- Entity representing the scope 482 483 Last_Subprogram_Name : String_Ptr; 484 -- Pointer to name of last subprogram body in this scope. Used for 485 -- testing proper alpha ordering of subprogram bodies in scope. 486 487 Save_Scope_Suppress : Suppress_Record; 488 -- Save contents of Scope_Suppress on entry 489 490 Save_Local_Suppress_Stack_Top : Suppress_Stack_Entry_Ptr; 491 -- Save contents of Local_Suppress_Stack on entry to restore on exit 492 493 Save_Check_Policy_List : Node_Id; 494 -- Save contents of Check_Policy_List on entry to restore on exit. The 495 -- Check_Policy pragmas are chained with Check_Policy_List pointing to 496 -- the most recent entry. This list is searched starting here, so that 497 -- the search finds the most recent appicable entry. When we restore 498 -- Check_Policy_List on exit from the scope, the effect is to remove 499 -- all entries set in the scope being exited. 500 501 Save_Default_Storage_Pool : Node_Id; 502 -- Save contents of Default_Storage_Pool on entry to restore on exit 503 504 Save_SPARK_Mode : SPARK_Mode_Type; 505 -- Setting of SPARK_Mode on entry to restore on exit 506 507 Save_SPARK_Mode_Pragma : Node_Id; 508 -- Setting of SPARK_Mode_Pragma on entry to restore on exit 509 510 Save_No_Tagged_Streams : Node_Id; 511 -- Setting of No_Tagged_Streams to restore on exit 512 513 Save_Default_SSO : Character; 514 -- Setting of Default_SSO on entry to restore on exit 515 516 Save_Uneval_Old : Character; 517 -- Setting of Uneval_Old on entry to restore on exit 518 519 Is_Transient : Boolean; 520 -- Marks transient scopes (see Exp_Ch7 body for details) 521 522 Previous_Visibility : Boolean; 523 -- Used when installing the parent(s) of the current compilation unit. 524 -- The parent may already be visible because of an ongoing compilation, 525 -- and the proper visibility must be restored on exit. The flag is 526 -- typically needed when the context of a child unit requires 527 -- compilation of a sibling. In other cases the flag is set to False. 528 -- See Sem_Ch10 (Install_Parents, Remove_Parents). 529 530 Node_To_Be_Wrapped : Node_Id; 531 -- Only used in transient scopes. Records the node which will be wrapped 532 -- by the transient block. 533 534 Actions_To_Be_Wrapped : Scope_Actions; 535 -- Actions that have to be inserted at the start, at the end, or as 536 -- cleanup actions of a transient block. Used to temporarily hold these 537 -- actions until the block is created, at which time the actions are 538 -- moved to the block. 539 540 Pending_Freeze_Actions : List_Id; 541 -- Used to collect freeze entity nodes and associated actions that are 542 -- generated in an inner context but need to be analyzed outside, such 543 -- as records and initialization procedures. On exit from the scope, 544 -- this list of actions is inserted before the scope construct and 545 -- analyzed to generate the corresponding freeze processing and 546 -- elaboration of other associated actions. 547 548 First_Use_Clause : Node_Id; 549 -- Head of list of Use_Clauses in current scope. The list is built when 550 -- the declarations in the scope are processed. The list is traversed 551 -- on scope exit to undo the effect of the use clauses. 552 553 Component_Alignment_Default : Component_Alignment_Kind; 554 -- Component alignment to be applied to any record or array types that 555 -- are declared for which a specific component alignment pragma does not 556 -- set the alignment. 557 558 Is_Active_Stack_Base : Boolean; 559 -- Set to true only when entering the scope for Standard_Standard from 560 -- from within procedure Semantics. Indicates the base of the current 561 -- active set of scopes. Needed by In_Open_Scopes to handle cases where 562 -- Standard_Standard can be pushed anew on the scope stack to start a 563 -- new active section (see comment above). 564 565 Locked_Shared_Objects : Elist_Id; 566 -- List of shared passive protected objects that have been locked in 567 -- this transient scope (always No_Elist for non-transient scopes). 568 end record; 569 570 package Scope_Stack is new Table.Table ( 571 Table_Component_Type => Scope_Stack_Entry, 572 Table_Index_Type => Int, 573 Table_Low_Bound => 0, 574 Table_Initial => Alloc.Scope_Stack_Initial, 575 Table_Increment => Alloc.Scope_Stack_Increment, 576 Table_Name => "Sem.Scope_Stack"); 577 578 ----------------- 579 -- Subprograms -- 580 ----------------- 581 582 procedure Initialize; 583 -- Initialize internal tables 584 585 procedure Lock; 586 -- Lock internal tables before calling back end 587 588 procedure Unlock; 589 -- Unlock internal tables 590 591 procedure Semantics (Comp_Unit : Node_Id); 592 -- This procedure is called to perform semantic analysis on the specified 593 -- node which is the N_Compilation_Unit node for the unit. 594 595 procedure Analyze (N : Node_Id); 596 procedure Analyze (N : Node_Id; Suppress : Check_Id); 597 -- This is the recursive procedure that is applied to individual nodes of 598 -- the tree, starting at the top level node (compilation unit node) and 599 -- then moving down the tree in a top down traversal. It calls individual 600 -- routines with names Analyze_xxx to analyze node xxx. Each of these 601 -- routines is responsible for calling Analyze on the components of the 602 -- subtree. 603 -- 604 -- Note: In the case of expression components (nodes whose Nkind is in 605 -- N_Subexpr), the call to Analyze does not complete the semantic analysis 606 -- of the node, since the type resolution cannot be completed until the 607 -- complete context is analyzed. The completion of the type analysis occurs 608 -- in the corresponding Resolve routine (see Sem_Res). 609 -- 610 -- Note: for integer and real literals, the analyzer sets the flag to 611 -- indicate that the result is a static expression. If the expander 612 -- generates a literal that does NOT correspond to a static expression, 613 -- e.g. by folding an expression whose value is known at compile time, 614 -- but is not technically static, then the caller should reset the 615 -- Is_Static_Expression flag after analyzing but before resolving. 616 -- 617 -- If the Suppress argument is present, then the analysis is done 618 -- with the specified check suppressed (can be All_Checks to suppress 619 -- all checks). 620 621 procedure Analyze_List (L : List_Id); 622 procedure Analyze_List (L : List_Id; Suppress : Check_Id); 623 -- Analyzes each element of a list. If the Suppress argument is present, 624 -- then the analysis is done with the specified check suppressed (can 625 -- be All_Checks to suppress all checks). 626 627 procedure Copy_Suppress_Status 628 (C : Check_Id; 629 From : Entity_Id; 630 To : Entity_Id); 631 -- If From is an entity for which check C is explicitly suppressed 632 -- then also explicitly suppress the corresponding check in To. 633 634 procedure Insert_List_After_And_Analyze 635 (N : Node_Id; L : List_Id); 636 -- Inserts list L after node N using Nlists.Insert_List_After, and then, 637 -- after this insertion is complete, analyzes all the nodes in the list, 638 -- including any additional nodes generated by this analysis. If the list 639 -- is empty or No_List, the call has no effect. 640 641 procedure Insert_List_Before_And_Analyze 642 (N : Node_Id; L : List_Id); 643 -- Inserts list L before node N using Nlists.Insert_List_Before, and then, 644 -- after this insertion is complete, analyzes all the nodes in the list, 645 -- including any additional nodes generated by this analysis. If the list 646 -- is empty or No_List, the call has no effect. 647 648 procedure Insert_After_And_Analyze 649 (N : Node_Id; M : Node_Id); 650 procedure Insert_After_And_Analyze 651 (N : Node_Id; M : Node_Id; Suppress : Check_Id); 652 -- Inserts node M after node N and then after the insertion is complete, 653 -- analyzes the inserted node and all nodes that are generated by 654 -- this analysis. If the node is empty, the call has no effect. If the 655 -- Suppress argument is present, then the analysis is done with the 656 -- specified check suppressed (can be All_Checks to suppress all checks). 657 658 procedure Insert_Before_And_Analyze 659 (N : Node_Id; M : Node_Id); 660 procedure Insert_Before_And_Analyze 661 (N : Node_Id; M : Node_Id; Suppress : Check_Id); 662 -- Inserts node M before node N and then after the insertion is complete, 663 -- analyzes the inserted node and all nodes that could be generated by 664 -- this analysis. If the node is empty, the call has no effect. If the 665 -- Suppress argument is present, then the analysis is done with the 666 -- specified check suppressed (can be All_Checks to suppress all checks). 667 668 function External_Ref_In_Generic (E : Entity_Id) return Boolean; 669 -- Return True if we are in the context of a generic and E is 670 -- external (more global) to it. 671 672 procedure Enter_Generic_Scope (S : Entity_Id); 673 -- Called each time a Generic subprogram or package scope is entered. S is 674 -- the entity of the scope. 675 -- 676 -- ??? At the moment, only called for package specs because this mechanism 677 -- is only used for avoiding freezing of external references in generics 678 -- and this can only be an issue if the outer generic scope is a package 679 -- spec (otherwise all external entities are already frozen) 680 681 procedure Exit_Generic_Scope (S : Entity_Id); 682 -- Called each time a Generic subprogram or package scope is exited. S is 683 -- the entity of the scope. 684 -- 685 -- ??? At the moment, only called for package specs exit. 686 687 function Explicit_Suppress (E : Entity_Id; C : Check_Id) return Boolean; 688 -- This function returns True if an explicit pragma Suppress for check C 689 -- is present in the package defining E. 690 691 function Preanalysis_Active return Boolean; 692 pragma Inline (Preanalysis_Active); 693 -- Determine whether preanalysis is active at the point of invocation 694 695 procedure Preanalyze (N : Node_Id); 696 -- Performs a preanalysis of node N. During preanalysis no expansion is 697 -- carried out for N or its children. See above for more info on 698 -- preanalysis. 699 700 generic 701 with procedure Action (Item : Node_Id); 702 procedure Walk_Library_Items; 703 -- Primarily for use by CodePeer and GNATprove. Must be called after 704 -- semantic analysis (and expansion in the case of CodePeer) are complete. 705 -- Walks each relevant library item, calling Action for each, in an order 706 -- such that one will not run across forward references. Each Item passed 707 -- to Action is the declaration or body of a library unit, including 708 -- generics and renamings. The first item is the N_Package_Declaration node 709 -- for package Standard. Bodies are not included, except for the main unit 710 -- itself, which always comes last. 711 -- 712 -- Item is never a subunit 713 -- 714 -- Item is never an instantiation. Instead, the instance declaration is 715 -- passed, and (if the instantiation is the main unit), the instance body. 716 717 ------------------------ 718 -- Debugging Routines -- 719 ------------------------ 720 721 function ss (Index : Int) return Scope_Stack_Entry; 722 pragma Export (Ada, ss); 723 -- "ss" = "scope stack"; returns the Index'th entry in the Scope_Stack 724 725 function sst return Scope_Stack_Entry; 726 pragma Export (Ada, sst); 727 -- "sst" = "scope stack top"; same as ss(Scope_Stack.Last) 728 729end Sem; 730