1//===- SymbolManager.h - Management of Symbolic Values --------------------===//
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 defines SymbolManager, a class that manages symbolic values
10//  created for use by ExprEngine and related classes.
11//
12//===----------------------------------------------------------------------===//
13
14#include "clang/StaticAnalyzer/Core/PathSensitive/SymbolManager.h"
15#include "clang/AST/ASTContext.h"
16#include "clang/AST/Expr.h"
17#include "clang/Analysis/Analyses/LiveVariables.h"
18#include "clang/Analysis/AnalysisDeclContext.h"
19#include "clang/Basic/LLVM.h"
20#include "clang/StaticAnalyzer/Core/PathSensitive/MemRegion.h"
21#include "clang/StaticAnalyzer/Core/PathSensitive/SVals.h"
22#include "clang/StaticAnalyzer/Core/PathSensitive/Store.h"
23#include "clang/StaticAnalyzer/Core/PathSensitive/SymExpr.h"
24#include "llvm/ADT/FoldingSet.h"
25#include "llvm/ADT/STLExtras.h"
26#include "llvm/Support/Casting.h"
27#include "llvm/Support/Compiler.h"
28#include "llvm/Support/ErrorHandling.h"
29#include "llvm/Support/raw_ostream.h"
30#include <cassert>
31
32using namespace clang;
33using namespace ento;
34
35void SymExpr::anchor() {}
36
37LLVM_DUMP_METHOD void SymExpr::dump() const { dumpToStream(llvm::errs()); }
38
39void BinarySymExpr::dumpToStreamImpl(raw_ostream &OS, const SymExpr *Sym) {
40  OS << '(';
41  Sym->dumpToStream(OS);
42  OS << ')';
43}
44
45void BinarySymExpr::dumpToStreamImpl(raw_ostream &OS,
46                                     const llvm::APSInt &Value) {
47  if (Value.isUnsigned())
48    OS << Value.getZExtValue();
49  else
50    OS << Value.getSExtValue();
51  if (Value.isUnsigned())
52    OS << 'U';
53}
54
55void BinarySymExpr::dumpToStreamImpl(raw_ostream &OS,
56                                     BinaryOperator::Opcode Op) {
57  OS << ' ' << BinaryOperator::getOpcodeStr(Op) << ' ';
58}
59
60void SymbolCast::dumpToStream(raw_ostream &os) const {
61  os << '(' << ToTy.getAsString() << ") (";
62  Operand->dumpToStream(os);
63  os << ')';
64}
65
66void SymbolConjured::dumpToStream(raw_ostream &os) const {
67  os << "conj_$" << getSymbolID() << '{' << T.getAsString() << ", LC"
68     << LCtx->getID();
69  if (S)
70    os << ", S" << S->getID(LCtx->getDecl()->getASTContext());
71  else
72    os << ", no stmt";
73  os << ", #" << Count << '}';
74}
75
76void SymbolDerived::dumpToStream(raw_ostream &os) const {
77  os << "derived_$" << getSymbolID() << '{'
78     << getParentSymbol() << ',' << getRegion() << '}';
79}
80
81void SymbolExtent::dumpToStream(raw_ostream &os) const {
82  os << "extent_$" << getSymbolID() << '{' << getRegion() << '}';
83}
84
85void SymbolMetadata::dumpToStream(raw_ostream &os) const {
86  os << "meta_$" << getSymbolID() << '{'
87     << getRegion() << ',' << T.getAsString() << '}';
88}
89
90void SymbolData::anchor() {}
91
92void SymbolRegionValue::dumpToStream(raw_ostream &os) const {
93  os << "reg_$" << getSymbolID()
94     << '<' << getType().getAsString() << ' ' << R << '>';
95}
96
97bool SymExpr::symbol_iterator::operator==(const symbol_iterator &X) const {
98  return itr == X.itr;
99}
100
101bool SymExpr::symbol_iterator::operator!=(const symbol_iterator &X) const {
102  return itr != X.itr;
103}
104
105SymExpr::symbol_iterator::symbol_iterator(const SymExpr *SE) {
106  itr.push_back(SE);
107}
108
109SymExpr::symbol_iterator &SymExpr::symbol_iterator::operator++() {
110  assert(!itr.empty() && "attempting to iterate on an 'end' iterator");
111  expand();
112  return *this;
113}
114
115SymbolRef SymExpr::symbol_iterator::operator*() {
116  assert(!itr.empty() && "attempting to dereference an 'end' iterator");
117  return itr.back();
118}
119
120void SymExpr::symbol_iterator::expand() {
121  const SymExpr *SE = itr.pop_back_val();
122
123  switch (SE->getKind()) {
124    case SymExpr::SymbolRegionValueKind:
125    case SymExpr::SymbolConjuredKind:
126    case SymExpr::SymbolDerivedKind:
127    case SymExpr::SymbolExtentKind:
128    case SymExpr::SymbolMetadataKind:
129      return;
130    case SymExpr::SymbolCastKind:
131      itr.push_back(cast<SymbolCast>(SE)->getOperand());
132      return;
133    case SymExpr::SymIntExprKind:
134      itr.push_back(cast<SymIntExpr>(SE)->getLHS());
135      return;
136    case SymExpr::IntSymExprKind:
137      itr.push_back(cast<IntSymExpr>(SE)->getRHS());
138      return;
139    case SymExpr::SymSymExprKind: {
140      const auto *x = cast<SymSymExpr>(SE);
141      itr.push_back(x->getLHS());
142      itr.push_back(x->getRHS());
143      return;
144    }
145  }
146  llvm_unreachable("unhandled expansion case");
147}
148
149const SymbolRegionValue*
150SymbolManager::getRegionValueSymbol(const TypedValueRegion* R) {
151  llvm::FoldingSetNodeID profile;
152  SymbolRegionValue::Profile(profile, R);
153  void *InsertPos;
154  SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
155  if (!SD) {
156    SD = (SymExpr*) BPAlloc.Allocate<SymbolRegionValue>();
157    new (SD) SymbolRegionValue(SymbolCounter, R);
158    DataSet.InsertNode(SD, InsertPos);
159    ++SymbolCounter;
160  }
161
162  return cast<SymbolRegionValue>(SD);
163}
164
165const SymbolConjured* SymbolManager::conjureSymbol(const Stmt *E,
166                                                   const LocationContext *LCtx,
167                                                   QualType T,
168                                                   unsigned Count,
169                                                   const void *SymbolTag) {
170  llvm::FoldingSetNodeID profile;
171  SymbolConjured::Profile(profile, E, T, Count, LCtx, SymbolTag);
172  void *InsertPos;
173  SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
174  if (!SD) {
175    SD = (SymExpr*) BPAlloc.Allocate<SymbolConjured>();
176    new (SD) SymbolConjured(SymbolCounter, E, LCtx, T, Count, SymbolTag);
177    DataSet.InsertNode(SD, InsertPos);
178    ++SymbolCounter;
179  }
180
181  return cast<SymbolConjured>(SD);
182}
183
184const SymbolDerived*
185SymbolManager::getDerivedSymbol(SymbolRef parentSymbol,
186                                const TypedValueRegion *R) {
187  llvm::FoldingSetNodeID profile;
188  SymbolDerived::Profile(profile, parentSymbol, R);
189  void *InsertPos;
190  SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
191  if (!SD) {
192    SD = (SymExpr*) BPAlloc.Allocate<SymbolDerived>();
193    new (SD) SymbolDerived(SymbolCounter, parentSymbol, R);
194    DataSet.InsertNode(SD, InsertPos);
195    ++SymbolCounter;
196  }
197
198  return cast<SymbolDerived>(SD);
199}
200
201const SymbolExtent*
202SymbolManager::getExtentSymbol(const SubRegion *R) {
203  llvm::FoldingSetNodeID profile;
204  SymbolExtent::Profile(profile, R);
205  void *InsertPos;
206  SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
207  if (!SD) {
208    SD = (SymExpr*) BPAlloc.Allocate<SymbolExtent>();
209    new (SD) SymbolExtent(SymbolCounter, R);
210    DataSet.InsertNode(SD, InsertPos);
211    ++SymbolCounter;
212  }
213
214  return cast<SymbolExtent>(SD);
215}
216
217const SymbolMetadata *
218SymbolManager::getMetadataSymbol(const MemRegion* R, const Stmt *S, QualType T,
219                                 const LocationContext *LCtx,
220                                 unsigned Count, const void *SymbolTag) {
221  llvm::FoldingSetNodeID profile;
222  SymbolMetadata::Profile(profile, R, S, T, LCtx, Count, SymbolTag);
223  void *InsertPos;
224  SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
225  if (!SD) {
226    SD = (SymExpr*) BPAlloc.Allocate<SymbolMetadata>();
227    new (SD) SymbolMetadata(SymbolCounter, R, S, T, LCtx, Count, SymbolTag);
228    DataSet.InsertNode(SD, InsertPos);
229    ++SymbolCounter;
230  }
231
232  return cast<SymbolMetadata>(SD);
233}
234
235const SymbolCast*
236SymbolManager::getCastSymbol(const SymExpr *Op,
237                             QualType From, QualType To) {
238  llvm::FoldingSetNodeID ID;
239  SymbolCast::Profile(ID, Op, From, To);
240  void *InsertPos;
241  SymExpr *data = DataSet.FindNodeOrInsertPos(ID, InsertPos);
242  if (!data) {
243    data = (SymbolCast*) BPAlloc.Allocate<SymbolCast>();
244    new (data) SymbolCast(Op, From, To);
245    DataSet.InsertNode(data, InsertPos);
246  }
247
248  return cast<SymbolCast>(data);
249}
250
251const SymIntExpr *SymbolManager::getSymIntExpr(const SymExpr *lhs,
252                                               BinaryOperator::Opcode op,
253                                               const llvm::APSInt& v,
254                                               QualType t) {
255  llvm::FoldingSetNodeID ID;
256  SymIntExpr::Profile(ID, lhs, op, v, t);
257  void *InsertPos;
258  SymExpr *data = DataSet.FindNodeOrInsertPos(ID, InsertPos);
259
260  if (!data) {
261    data = (SymIntExpr*) BPAlloc.Allocate<SymIntExpr>();
262    new (data) SymIntExpr(lhs, op, v, t);
263    DataSet.InsertNode(data, InsertPos);
264  }
265
266  return cast<SymIntExpr>(data);
267}
268
269const IntSymExpr *SymbolManager::getIntSymExpr(const llvm::APSInt& lhs,
270                                               BinaryOperator::Opcode op,
271                                               const SymExpr *rhs,
272                                               QualType t) {
273  llvm::FoldingSetNodeID ID;
274  IntSymExpr::Profile(ID, lhs, op, rhs, t);
275  void *InsertPos;
276  SymExpr *data = DataSet.FindNodeOrInsertPos(ID, InsertPos);
277
278  if (!data) {
279    data = (IntSymExpr*) BPAlloc.Allocate<IntSymExpr>();
280    new (data) IntSymExpr(lhs, op, rhs, t);
281    DataSet.InsertNode(data, InsertPos);
282  }
283
284  return cast<IntSymExpr>(data);
285}
286
287const SymSymExpr *SymbolManager::getSymSymExpr(const SymExpr *lhs,
288                                               BinaryOperator::Opcode op,
289                                               const SymExpr *rhs,
290                                               QualType t) {
291  llvm::FoldingSetNodeID ID;
292  SymSymExpr::Profile(ID, lhs, op, rhs, t);
293  void *InsertPos;
294  SymExpr *data = DataSet.FindNodeOrInsertPos(ID, InsertPos);
295
296  if (!data) {
297    data = (SymSymExpr*) BPAlloc.Allocate<SymSymExpr>();
298    new (data) SymSymExpr(lhs, op, rhs, t);
299    DataSet.InsertNode(data, InsertPos);
300  }
301
302  return cast<SymSymExpr>(data);
303}
304
305QualType SymbolConjured::getType() const {
306  return T;
307}
308
309QualType SymbolDerived::getType() const {
310  return R->getValueType();
311}
312
313QualType SymbolExtent::getType() const {
314  ASTContext &Ctx = R->getMemRegionManager().getContext();
315  return Ctx.getSizeType();
316}
317
318QualType SymbolMetadata::getType() const {
319  return T;
320}
321
322QualType SymbolRegionValue::getType() const {
323  return R->getValueType();
324}
325
326bool SymbolManager::canSymbolicate(QualType T) {
327  T = T.getCanonicalType();
328
329  if (Loc::isLocType(T))
330    return true;
331
332  if (T->isIntegralOrEnumerationType())
333    return true;
334
335  if (T->isRecordType() && !T->isUnionType())
336    return true;
337
338  return false;
339}
340
341void SymbolManager::addSymbolDependency(const SymbolRef Primary,
342                                        const SymbolRef Dependent) {
343  auto &dependencies = SymbolDependencies[Primary];
344  if (!dependencies) {
345    dependencies = std::make_unique<SymbolRefSmallVectorTy>();
346  }
347  dependencies->push_back(Dependent);
348}
349
350const SymbolRefSmallVectorTy *SymbolManager::getDependentSymbols(
351                                                     const SymbolRef Primary) {
352  SymbolDependTy::const_iterator I = SymbolDependencies.find(Primary);
353  if (I == SymbolDependencies.end())
354    return nullptr;
355  return I->second.get();
356}
357
358void SymbolReaper::markDependentsLive(SymbolRef sym) {
359  // Do not mark dependents more then once.
360  SymbolMapTy::iterator LI = TheLiving.find(sym);
361  assert(LI != TheLiving.end() && "The primary symbol is not live.");
362  if (LI->second == HaveMarkedDependents)
363    return;
364  LI->second = HaveMarkedDependents;
365
366  if (const SymbolRefSmallVectorTy *Deps = SymMgr.getDependentSymbols(sym)) {
367    for (const auto I : *Deps) {
368      if (TheLiving.find(I) != TheLiving.end())
369        continue;
370      markLive(I);
371    }
372  }
373}
374
375void SymbolReaper::markLive(SymbolRef sym) {
376  TheLiving[sym] = NotProcessed;
377  markDependentsLive(sym);
378}
379
380void SymbolReaper::markLive(const MemRegion *region) {
381  RegionRoots.insert(region->getBaseRegion());
382  markElementIndicesLive(region);
383}
384
385void SymbolReaper::markElementIndicesLive(const MemRegion *region) {
386  for (auto SR = dyn_cast<SubRegion>(region); SR;
387       SR = dyn_cast<SubRegion>(SR->getSuperRegion())) {
388    if (const auto ER = dyn_cast<ElementRegion>(SR)) {
389      SVal Idx = ER->getIndex();
390      for (auto SI = Idx.symbol_begin(), SE = Idx.symbol_end(); SI != SE; ++SI)
391        markLive(*SI);
392    }
393  }
394}
395
396void SymbolReaper::markInUse(SymbolRef sym) {
397  if (isa<SymbolMetadata>(sym))
398    MetadataInUse.insert(sym);
399}
400
401bool SymbolReaper::isLiveRegion(const MemRegion *MR) {
402  // TODO: For now, liveness of a memory region is equivalent to liveness of its
403  // base region. In fact we can do a bit better: say, if a particular FieldDecl
404  // is not used later in the path, we can diagnose a leak of a value within
405  // that field earlier than, say, the variable that contains the field dies.
406  MR = MR->getBaseRegion();
407
408  if (RegionRoots.count(MR))
409    return true;
410
411  if (const auto *SR = dyn_cast<SymbolicRegion>(MR))
412    return isLive(SR->getSymbol());
413
414  if (const auto *VR = dyn_cast<VarRegion>(MR))
415    return isLive(VR, true);
416
417  // FIXME: This is a gross over-approximation. What we really need is a way to
418  // tell if anything still refers to this region. Unlike SymbolicRegions,
419  // AllocaRegions don't have associated symbols, though, so we don't actually
420  // have a way to track their liveness.
421  if (isa<AllocaRegion>(MR))
422    return true;
423
424  if (isa<CXXThisRegion>(MR))
425    return true;
426
427  if (isa<MemSpaceRegion>(MR))
428    return true;
429
430  if (isa<CodeTextRegion>(MR))
431    return true;
432
433  return false;
434}
435
436bool SymbolReaper::isLive(SymbolRef sym) {
437  if (TheLiving.count(sym)) {
438    markDependentsLive(sym);
439    return true;
440  }
441
442  bool KnownLive;
443
444  switch (sym->getKind()) {
445  case SymExpr::SymbolRegionValueKind:
446    KnownLive = isLiveRegion(cast<SymbolRegionValue>(sym)->getRegion());
447    break;
448  case SymExpr::SymbolConjuredKind:
449    KnownLive = false;
450    break;
451  case SymExpr::SymbolDerivedKind:
452    KnownLive = isLive(cast<SymbolDerived>(sym)->getParentSymbol());
453    break;
454  case SymExpr::SymbolExtentKind:
455    KnownLive = isLiveRegion(cast<SymbolExtent>(sym)->getRegion());
456    break;
457  case SymExpr::SymbolMetadataKind:
458    KnownLive = MetadataInUse.count(sym) &&
459                isLiveRegion(cast<SymbolMetadata>(sym)->getRegion());
460    if (KnownLive)
461      MetadataInUse.erase(sym);
462    break;
463  case SymExpr::SymIntExprKind:
464    KnownLive = isLive(cast<SymIntExpr>(sym)->getLHS());
465    break;
466  case SymExpr::IntSymExprKind:
467    KnownLive = isLive(cast<IntSymExpr>(sym)->getRHS());
468    break;
469  case SymExpr::SymSymExprKind:
470    KnownLive = isLive(cast<SymSymExpr>(sym)->getLHS()) &&
471                isLive(cast<SymSymExpr>(sym)->getRHS());
472    break;
473  case SymExpr::SymbolCastKind:
474    KnownLive = isLive(cast<SymbolCast>(sym)->getOperand());
475    break;
476  }
477
478  if (KnownLive)
479    markLive(sym);
480
481  return KnownLive;
482}
483
484bool
485SymbolReaper::isLive(const Stmt *ExprVal, const LocationContext *ELCtx) const {
486  if (LCtx == nullptr)
487    return false;
488
489  if (LCtx != ELCtx) {
490    // If the reaper's location context is a parent of the expression's
491    // location context, then the expression value is now "out of scope".
492    if (LCtx->isParentOf(ELCtx))
493      return false;
494    return true;
495  }
496
497  // If no statement is provided, everything is this and parent contexts is live.
498  if (!Loc)
499    return true;
500
501  return LCtx->getAnalysis<RelaxedLiveVariables>()->isLive(Loc, ExprVal);
502}
503
504bool SymbolReaper::isLive(const VarRegion *VR, bool includeStoreBindings) const{
505  const StackFrameContext *VarContext = VR->getStackFrame();
506
507  if (!VarContext)
508    return true;
509
510  if (!LCtx)
511    return false;
512  const StackFrameContext *CurrentContext = LCtx->getStackFrame();
513
514  if (VarContext == CurrentContext) {
515    // If no statement is provided, everything is live.
516    if (!Loc)
517      return true;
518
519    // Anonymous parameters of an inheriting constructor are live for the entire
520    // duration of the constructor.
521    if (isa<CXXInheritedCtorInitExpr>(Loc))
522      return true;
523
524    if (LCtx->getAnalysis<RelaxedLiveVariables>()->isLive(Loc, VR->getDecl()))
525      return true;
526
527    if (!includeStoreBindings)
528      return false;
529
530    unsigned &cachedQuery =
531      const_cast<SymbolReaper *>(this)->includedRegionCache[VR];
532
533    if (cachedQuery) {
534      return cachedQuery == 1;
535    }
536
537    // Query the store to see if the region occurs in any live bindings.
538    if (Store store = reapedStore.getStore()) {
539      bool hasRegion =
540        reapedStore.getStoreManager().includedInBindings(store, VR);
541      cachedQuery = hasRegion ? 1 : 2;
542      return hasRegion;
543    }
544
545    return false;
546  }
547
548  return VarContext->isParentOf(CurrentContext);
549}
550