1//===- IdentifierResolver.cpp - Lexical Scope Name lookup -----------------===//
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// This file implements the IdentifierResolver class, which is used for lexical
10// scoped lookup, based on declaration names.
11//
12//===----------------------------------------------------------------------===//
13
14#include "clang/Sema/IdentifierResolver.h"
15#include "clang/AST/Decl.h"
16#include "clang/AST/DeclBase.h"
17#include "clang/AST/DeclarationName.h"
18#include "clang/Basic/IdentifierTable.h"
19#include "clang/Basic/LangOptions.h"
20#include "clang/Lex/ExternalPreprocessorSource.h"
21#include "clang/Lex/Preprocessor.h"
22#include "clang/Sema/Scope.h"
23#include "llvm/Support/ErrorHandling.h"
24#include <cassert>
25#include <cstdint>
26
27using namespace clang;
28
29//===----------------------------------------------------------------------===//
30// IdDeclInfoMap class
31//===----------------------------------------------------------------------===//
32
33/// IdDeclInfoMap - Associates IdDeclInfos with declaration names.
34/// Allocates 'pools' (vectors of IdDeclInfos) to avoid allocating each
35/// individual IdDeclInfo to heap.
36class IdentifierResolver::IdDeclInfoMap {
37  static const unsigned int POOL_SIZE = 512;
38
39  /// We use our own linked-list implementation because it is sadly
40  /// impossible to add something to a pre-C++0x STL container without
41  /// a completely unnecessary copy.
42  struct IdDeclInfoPool {
43    IdDeclInfoPool *Next;
44    IdDeclInfo Pool[POOL_SIZE];
45
46    IdDeclInfoPool(IdDeclInfoPool *Next) : Next(Next) {}
47  };
48
49  IdDeclInfoPool *CurPool = nullptr;
50  unsigned int CurIndex = POOL_SIZE;
51
52public:
53  IdDeclInfoMap() = default;
54
55  ~IdDeclInfoMap() {
56    IdDeclInfoPool *Cur = CurPool;
57    while (IdDeclInfoPool *P = Cur) {
58      Cur = Cur->Next;
59      delete P;
60    }
61  }
62
63  /// Returns the IdDeclInfo associated to the DeclarationName.
64  /// It creates a new IdDeclInfo if one was not created before for this id.
65  IdDeclInfo &operator[](DeclarationName Name);
66};
67
68//===----------------------------------------------------------------------===//
69// IdDeclInfo Implementation
70//===----------------------------------------------------------------------===//
71
72/// RemoveDecl - Remove the decl from the scope chain.
73/// The decl must already be part of the decl chain.
74void IdentifierResolver::IdDeclInfo::RemoveDecl(NamedDecl *D) {
75  for (DeclsTy::iterator I = Decls.end(); I != Decls.begin(); --I) {
76    if (D == *(I-1)) {
77      Decls.erase(I-1);
78      return;
79    }
80  }
81
82  llvm_unreachable("Didn't find this decl on its identifier's chain!");
83}
84
85//===----------------------------------------------------------------------===//
86// IdentifierResolver Implementation
87//===----------------------------------------------------------------------===//
88
89IdentifierResolver::IdentifierResolver(Preprocessor &PP)
90    : LangOpt(PP.getLangOpts()), PP(PP), IdDeclInfos(new IdDeclInfoMap) {}
91
92IdentifierResolver::~IdentifierResolver() {
93  delete IdDeclInfos;
94}
95
96/// isDeclInScope - If 'Ctx' is a function/method, isDeclInScope returns true
97/// if 'D' is in Scope 'S', otherwise 'S' is ignored and isDeclInScope returns
98/// true if 'D' belongs to the given declaration context.
99bool IdentifierResolver::isDeclInScope(Decl *D, DeclContext *Ctx, Scope *S,
100                                       bool AllowInlineNamespace) const {
101  Ctx = Ctx->getRedeclContext();
102
103  if (Ctx->isFunctionOrMethod() || (S && S->isFunctionPrototypeScope())) {
104    // Ignore the scopes associated within transparent declaration contexts.
105    while (S->getEntity() && S->getEntity()->isTransparentContext())
106      S = S->getParent();
107
108    if (S->isDeclScope(D))
109      return true;
110    if (LangOpt.CPlusPlus) {
111      // C++ 3.3.2p3:
112      // The name declared in a catch exception-declaration is local to the
113      // handler and shall not be redeclared in the outermost block of the
114      // handler.
115      // C++ 3.3.2p4:
116      // Names declared in the for-init-statement, and in the condition of if,
117      // while, for, and switch statements are local to the if, while, for, or
118      // switch statement (including the controlled statement), and shall not be
119      // redeclared in a subsequent condition of that statement nor in the
120      // outermost block (or, for the if statement, any of the outermost blocks)
121      // of the controlled statement.
122      //
123      assert(S->getParent() && "No TUScope?");
124      if (S->getParent()->getFlags() & Scope::ControlScope) {
125        S = S->getParent();
126        if (S->isDeclScope(D))
127          return true;
128      }
129      if (S->getFlags() & Scope::FnTryCatchScope)
130        return S->getParent()->isDeclScope(D);
131    }
132    return false;
133  }
134
135  // FIXME: If D is a local extern declaration, this check doesn't make sense;
136  // we should be checking its lexical context instead in that case, because
137  // that is its scope.
138  DeclContext *DCtx = D->getDeclContext()->getRedeclContext();
139  return AllowInlineNamespace ? Ctx->InEnclosingNamespaceSetOf(DCtx)
140                              : Ctx->Equals(DCtx);
141}
142
143/// AddDecl - Link the decl to its shadowed decl chain.
144void IdentifierResolver::AddDecl(NamedDecl *D) {
145  DeclarationName Name = D->getDeclName();
146  if (IdentifierInfo *II = Name.getAsIdentifierInfo())
147    updatingIdentifier(*II);
148
149  void *Ptr = Name.getFETokenInfo();
150
151  if (!Ptr) {
152    Name.setFETokenInfo(D);
153    return;
154  }
155
156  IdDeclInfo *IDI;
157
158  if (isDeclPtr(Ptr)) {
159    Name.setFETokenInfo(nullptr);
160    IDI = &(*IdDeclInfos)[Name];
161    NamedDecl *PrevD = static_cast<NamedDecl*>(Ptr);
162    IDI->AddDecl(PrevD);
163  } else
164    IDI = toIdDeclInfo(Ptr);
165
166  IDI->AddDecl(D);
167}
168
169void IdentifierResolver::InsertDeclAfter(iterator Pos, NamedDecl *D) {
170  DeclarationName Name = D->getDeclName();
171  if (IdentifierInfo *II = Name.getAsIdentifierInfo())
172    updatingIdentifier(*II);
173
174  void *Ptr = Name.getFETokenInfo();
175
176  if (!Ptr) {
177    AddDecl(D);
178    return;
179  }
180
181  if (isDeclPtr(Ptr)) {
182    // We only have a single declaration: insert before or after it,
183    // as appropriate.
184    if (Pos == iterator()) {
185      // Add the new declaration before the existing declaration.
186      NamedDecl *PrevD = static_cast<NamedDecl*>(Ptr);
187      RemoveDecl(PrevD);
188      AddDecl(D);
189      AddDecl(PrevD);
190    } else {
191      // Add new declaration after the existing declaration.
192      AddDecl(D);
193    }
194
195    return;
196  }
197
198  // General case: insert the declaration at the appropriate point in the
199  // list, which already has at least two elements.
200  IdDeclInfo *IDI = toIdDeclInfo(Ptr);
201  if (Pos.isIterator()) {
202    IDI->InsertDecl(Pos.getIterator() + 1, D);
203  } else
204    IDI->InsertDecl(IDI->decls_begin(), D);
205}
206
207/// RemoveDecl - Unlink the decl from its shadowed decl chain.
208/// The decl must already be part of the decl chain.
209void IdentifierResolver::RemoveDecl(NamedDecl *D) {
210  assert(D && "null param passed");
211  DeclarationName Name = D->getDeclName();
212  if (IdentifierInfo *II = Name.getAsIdentifierInfo())
213    updatingIdentifier(*II);
214
215  void *Ptr = Name.getFETokenInfo();
216
217  assert(Ptr && "Didn't find this decl on its identifier's chain!");
218
219  if (isDeclPtr(Ptr)) {
220    assert(D == Ptr && "Didn't find this decl on its identifier's chain!");
221    Name.setFETokenInfo(nullptr);
222    return;
223  }
224
225  return toIdDeclInfo(Ptr)->RemoveDecl(D);
226}
227
228/// begin - Returns an iterator for decls with name 'Name'.
229IdentifierResolver::iterator
230IdentifierResolver::begin(DeclarationName Name) {
231  if (IdentifierInfo *II = Name.getAsIdentifierInfo())
232    readingIdentifier(*II);
233
234  void *Ptr = Name.getFETokenInfo();
235  if (!Ptr) return end();
236
237  if (isDeclPtr(Ptr))
238    return iterator(static_cast<NamedDecl*>(Ptr));
239
240  IdDeclInfo *IDI = toIdDeclInfo(Ptr);
241
242  IdDeclInfo::DeclsTy::iterator I = IDI->decls_end();
243  if (I != IDI->decls_begin())
244    return iterator(I-1);
245  // No decls found.
246  return end();
247}
248
249namespace {
250
251enum DeclMatchKind {
252  DMK_Different,
253  DMK_Replace,
254  DMK_Ignore
255};
256
257} // namespace
258
259/// Compare two declarations to see whether they are different or,
260/// if they are the same, whether the new declaration should replace the
261/// existing declaration.
262static DeclMatchKind compareDeclarations(NamedDecl *Existing, NamedDecl *New) {
263  // If the declarations are identical, ignore the new one.
264  if (Existing == New)
265    return DMK_Ignore;
266
267  // If the declarations have different kinds, they're obviously different.
268  if (Existing->getKind() != New->getKind())
269    return DMK_Different;
270
271  // If the declarations are redeclarations of each other, keep the newest one.
272  if (Existing->getCanonicalDecl() == New->getCanonicalDecl()) {
273    // If we're adding an imported declaration, don't replace another imported
274    // declaration.
275    if (Existing->isFromASTFile() && New->isFromASTFile())
276      return DMK_Different;
277
278    // If either of these is the most recent declaration, use it.
279    Decl *MostRecent = Existing->getMostRecentDecl();
280    if (Existing == MostRecent)
281      return DMK_Ignore;
282
283    if (New == MostRecent)
284      return DMK_Replace;
285
286    // If the existing declaration is somewhere in the previous declaration
287    // chain of the new declaration, then prefer the new declaration.
288    for (auto RD : New->redecls()) {
289      if (RD == Existing)
290        return DMK_Replace;
291
292      if (RD->isCanonicalDecl())
293        break;
294    }
295
296    return DMK_Ignore;
297  }
298
299  return DMK_Different;
300}
301
302bool IdentifierResolver::tryAddTopLevelDecl(NamedDecl *D, DeclarationName Name){
303  if (IdentifierInfo *II = Name.getAsIdentifierInfo())
304    readingIdentifier(*II);
305
306  void *Ptr = Name.getFETokenInfo();
307
308  if (!Ptr) {
309    Name.setFETokenInfo(D);
310    return true;
311  }
312
313  IdDeclInfo *IDI;
314
315  if (isDeclPtr(Ptr)) {
316    NamedDecl *PrevD = static_cast<NamedDecl*>(Ptr);
317
318    switch (compareDeclarations(PrevD, D)) {
319    case DMK_Different:
320      break;
321
322    case DMK_Ignore:
323      return false;
324
325    case DMK_Replace:
326      Name.setFETokenInfo(D);
327      return true;
328    }
329
330    Name.setFETokenInfo(nullptr);
331    IDI = &(*IdDeclInfos)[Name];
332
333    // If the existing declaration is not visible in translation unit scope,
334    // then add the new top-level declaration first.
335    if (!PrevD->getDeclContext()->getRedeclContext()->isTranslationUnit()) {
336      IDI->AddDecl(D);
337      IDI->AddDecl(PrevD);
338    } else {
339      IDI->AddDecl(PrevD);
340      IDI->AddDecl(D);
341    }
342    return true;
343  }
344
345  IDI = toIdDeclInfo(Ptr);
346
347  // See whether this declaration is identical to any existing declarations.
348  // If not, find the right place to insert it.
349  for (IdDeclInfo::DeclsTy::iterator I = IDI->decls_begin(),
350                                  IEnd = IDI->decls_end();
351       I != IEnd; ++I) {
352
353    switch (compareDeclarations(*I, D)) {
354    case DMK_Different:
355      break;
356
357    case DMK_Ignore:
358      return false;
359
360    case DMK_Replace:
361      *I = D;
362      return true;
363    }
364
365    if (!(*I)->getDeclContext()->getRedeclContext()->isTranslationUnit()) {
366      // We've found a declaration that is not visible from the translation
367      // unit (it's in an inner scope). Insert our declaration here.
368      IDI->InsertDecl(I, D);
369      return true;
370    }
371  }
372
373  // Add the declaration to the end.
374  IDI->AddDecl(D);
375  return true;
376}
377
378void IdentifierResolver::readingIdentifier(IdentifierInfo &II) {
379  if (II.isOutOfDate())
380    PP.getExternalSource()->updateOutOfDateIdentifier(II);
381}
382
383void IdentifierResolver::updatingIdentifier(IdentifierInfo &II) {
384  if (II.isOutOfDate())
385    PP.getExternalSource()->updateOutOfDateIdentifier(II);
386
387  if (II.isFromAST())
388    II.setFETokenInfoChangedSinceDeserialization();
389}
390
391//===----------------------------------------------------------------------===//
392// IdDeclInfoMap Implementation
393//===----------------------------------------------------------------------===//
394
395/// Returns the IdDeclInfo associated to the DeclarationName.
396/// It creates a new IdDeclInfo if one was not created before for this id.
397IdentifierResolver::IdDeclInfo &
398IdentifierResolver::IdDeclInfoMap::operator[](DeclarationName Name) {
399  void *Ptr = Name.getFETokenInfo();
400
401  if (Ptr) return *toIdDeclInfo(Ptr);
402
403  if (CurIndex == POOL_SIZE) {
404    CurPool = new IdDeclInfoPool(CurPool);
405    CurIndex = 0;
406  }
407  IdDeclInfo *IDI = &CurPool->Pool[CurIndex];
408  Name.setFETokenInfo(reinterpret_cast<void*>(
409                              reinterpret_cast<uintptr_t>(IDI) | 0x1)
410                                                                     );
411  ++CurIndex;
412  return *IDI;
413}
414
415void IdentifierResolver::iterator::incrementSlowCase() {
416  NamedDecl *D = **this;
417  void *InfoPtr = D->getDeclName().getFETokenInfo();
418  assert(!isDeclPtr(InfoPtr) && "Decl with wrong id ?");
419  IdDeclInfo *Info = toIdDeclInfo(InfoPtr);
420
421  BaseIter I = getIterator();
422  if (I != Info->decls_begin())
423    *this = iterator(I-1);
424  else // No more decls.
425    *this = iterator();
426}
427