AnalysisBasedWarnings.cpp revision e4e68d45f89ff4899d30cbd196603d09b7fbc150 
1//=- AnalysisBasedWarnings.cpp - Sema warnings based on libAnalysis -*- C++ -*-=//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file defines analysis_warnings::[Policy,Executor].
11// Together they are used by Sema to issue warnings based on inexpensive
12// static analysis algorithms in libAnalysis.
13//
14//===----------------------------------------------------------------------===//
15
16#include "clang/Sema/AnalysisBasedWarnings.h"
17#include "clang/Sema/SemaInternal.h"
18#include "clang/Sema/ScopeInfo.h"
19#include "clang/Basic/SourceManager.h"
20#include "clang/Basic/SourceLocation.h"
21#include "clang/Lex/Preprocessor.h"
22#include "clang/AST/DeclObjC.h"
23#include "clang/AST/DeclCXX.h"
24#include "clang/AST/ExprObjC.h"
25#include "clang/AST/ExprCXX.h"
26#include "clang/AST/StmtObjC.h"
27#include "clang/AST/StmtCXX.h"
28#include "clang/AST/EvaluatedExprVisitor.h"
29#include "clang/AST/StmtVisitor.h"
30#include "clang/Analysis/AnalysisContext.h"
31#include "clang/Analysis/CFG.h"
32#include "clang/Analysis/Analyses/ReachableCode.h"
33#include "clang/Analysis/Analyses/CFGReachabilityAnalysis.h"
34#include "clang/Analysis/Analyses/ThreadSafety.h"
35#include "clang/Analysis/CFGStmtMap.h"
36#include "clang/Analysis/Analyses/UninitializedValues.h"
37#include "llvm/ADT/BitVector.h"
38#include "llvm/ADT/FoldingSet.h"
39#include "llvm/ADT/ImmutableMap.h"
40#include "llvm/ADT/PostOrderIterator.h"
41#include "llvm/ADT/SmallVector.h"
42#include "llvm/ADT/StringRef.h"
43#include "llvm/Support/Casting.h"
44#include <algorithm>
45#include <vector>
46
47using namespace clang;
48
49//===----------------------------------------------------------------------===//
50// Unreachable code analysis.
51//===----------------------------------------------------------------------===//
52
53namespace {
54  class UnreachableCodeHandler : public reachable_code::Callback {
55    Sema &S;
56  public:
57    UnreachableCodeHandler(Sema &s) : S(s) {}
58
59    void HandleUnreachable(SourceLocation L, SourceRange R1, SourceRange R2) {
60      S.Diag(L, diag::warn_unreachable) << R1 << R2;
61    }
62  };
63}
64
65/// CheckUnreachable - Check for unreachable code.
66static void CheckUnreachable(Sema &S, AnalysisDeclContext &AC) {
67  UnreachableCodeHandler UC(S);
68  reachable_code::FindUnreachableCode(AC, UC);
69}
70
71//===----------------------------------------------------------------------===//
72// Check for missing return value.
73//===----------------------------------------------------------------------===//
74
75enum ControlFlowKind {
76  UnknownFallThrough,
77  NeverFallThrough,
78  MaybeFallThrough,
79  AlwaysFallThrough,
80  NeverFallThroughOrReturn
81};
82
83/// CheckFallThrough - Check that we don't fall off the end of a
84/// Statement that should return a value.
85///
86/// \returns AlwaysFallThrough iff we always fall off the end of the statement,
87/// MaybeFallThrough iff we might or might not fall off the end,
88/// NeverFallThroughOrReturn iff we never fall off the end of the statement or
89/// return.  We assume NeverFallThrough iff we never fall off the end of the
90/// statement but we may return.  We assume that functions not marked noreturn
91/// will return.
92static ControlFlowKind CheckFallThrough(AnalysisDeclContext &AC) {
93  CFG *cfg = AC.getCFG();
94  if (cfg == 0) return UnknownFallThrough;
95
96  // The CFG leaves in dead things, and we don't want the dead code paths to
97  // confuse us, so we mark all live things first.
98  llvm::BitVector live(cfg->getNumBlockIDs());
99  unsigned count = reachable_code::ScanReachableFromBlock(&cfg->getEntry(),
100                                                          live);
101
102  bool AddEHEdges = AC.getAddEHEdges();
103  if (!AddEHEdges && count != cfg->getNumBlockIDs())
104    // When there are things remaining dead, and we didn't add EH edges
105    // from CallExprs to the catch clauses, we have to go back and
106    // mark them as live.
107    for (CFG::iterator I = cfg->begin(), E = cfg->end(); I != E; ++I) {
108      CFGBlock &b = **I;
109      if (!live[b.getBlockID()]) {
110        if (b.pred_begin() == b.pred_end()) {
111          if (b.getTerminator() && isa<CXXTryStmt>(b.getTerminator()))
112            // When not adding EH edges from calls, catch clauses
113            // can otherwise seem dead.  Avoid noting them as dead.
114            count += reachable_code::ScanReachableFromBlock(&b, live);
115          continue;
116        }
117      }
118    }
119
120  // Now we know what is live, we check the live precessors of the exit block
121  // and look for fall through paths, being careful to ignore normal returns,
122  // and exceptional paths.
123  bool HasLiveReturn = false;
124  bool HasFakeEdge = false;
125  bool HasPlainEdge = false;
126  bool HasAbnormalEdge = false;
127
128  // Ignore default cases that aren't likely to be reachable because all
129  // enums in a switch(X) have explicit case statements.
130  CFGBlock::FilterOptions FO;
131  FO.IgnoreDefaultsWithCoveredEnums = 1;
132
133  for (CFGBlock::filtered_pred_iterator
134	 I = cfg->getExit().filtered_pred_start_end(FO); I.hasMore(); ++I) {
135    const CFGBlock& B = **I;
136    if (!live[B.getBlockID()])
137      continue;
138
139    // Skip blocks which contain an element marked as no-return. They don't
140    // represent actually viable edges into the exit block, so mark them as
141    // abnormal.
142    if (B.hasNoReturnElement()) {
143      HasAbnormalEdge = true;
144      continue;
145    }
146
147    // Destructors can appear after the 'return' in the CFG.  This is
148    // normal.  We need to look pass the destructors for the return
149    // statement (if it exists).
150    CFGBlock::const_reverse_iterator ri = B.rbegin(), re = B.rend();
151
152    for ( ; ri != re ; ++ri)
153      if (isa<CFGStmt>(*ri))
154        break;
155
156    // No more CFGElements in the block?
157    if (ri == re) {
158      if (B.getTerminator() && isa<CXXTryStmt>(B.getTerminator())) {
159        HasAbnormalEdge = true;
160        continue;
161      }
162      // A labeled empty statement, or the entry block...
163      HasPlainEdge = true;
164      continue;
165    }
166
167    CFGStmt CS = cast<CFGStmt>(*ri);
168    const Stmt *S = CS.getStmt();
169    if (isa<ReturnStmt>(S)) {
170      HasLiveReturn = true;
171      continue;
172    }
173    if (isa<ObjCAtThrowStmt>(S)) {
174      HasFakeEdge = true;
175      continue;
176    }
177    if (isa<CXXThrowExpr>(S)) {
178      HasFakeEdge = true;
179      continue;
180    }
181    if (const AsmStmt *AS = dyn_cast<AsmStmt>(S)) {
182      if (AS->isMSAsm()) {
183        HasFakeEdge = true;
184        HasLiveReturn = true;
185        continue;
186      }
187    }
188    if (isa<CXXTryStmt>(S)) {
189      HasAbnormalEdge = true;
190      continue;
191    }
192    if (std::find(B.succ_begin(), B.succ_end(), &cfg->getExit())
193        == B.succ_end()) {
194      HasAbnormalEdge = true;
195      continue;
196    }
197
198    HasPlainEdge = true;
199  }
200  if (!HasPlainEdge) {
201    if (HasLiveReturn)
202      return NeverFallThrough;
203    return NeverFallThroughOrReturn;
204  }
205  if (HasAbnormalEdge || HasFakeEdge || HasLiveReturn)
206    return MaybeFallThrough;
207  // This says AlwaysFallThrough for calls to functions that are not marked
208  // noreturn, that don't return.  If people would like this warning to be more
209  // accurate, such functions should be marked as noreturn.
210  return AlwaysFallThrough;
211}
212
213namespace {
214
215struct CheckFallThroughDiagnostics {
216  unsigned diag_MaybeFallThrough_HasNoReturn;
217  unsigned diag_MaybeFallThrough_ReturnsNonVoid;
218  unsigned diag_AlwaysFallThrough_HasNoReturn;
219  unsigned diag_AlwaysFallThrough_ReturnsNonVoid;
220  unsigned diag_NeverFallThroughOrReturn;
221  enum { Function, Block, Lambda } funMode;
222  SourceLocation FuncLoc;
223
224  static CheckFallThroughDiagnostics MakeForFunction(const Decl *Func) {
225    CheckFallThroughDiagnostics D;
226    D.FuncLoc = Func->getLocation();
227    D.diag_MaybeFallThrough_HasNoReturn =
228      diag::warn_falloff_noreturn_function;
229    D.diag_MaybeFallThrough_ReturnsNonVoid =
230      diag::warn_maybe_falloff_nonvoid_function;
231    D.diag_AlwaysFallThrough_HasNoReturn =
232      diag::warn_falloff_noreturn_function;
233    D.diag_AlwaysFallThrough_ReturnsNonVoid =
234      diag::warn_falloff_nonvoid_function;
235
236    // Don't suggest that virtual functions be marked "noreturn", since they
237    // might be overridden by non-noreturn functions.
238    bool isVirtualMethod = false;
239    if (const CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(Func))
240      isVirtualMethod = Method->isVirtual();
241
242    // Don't suggest that template instantiations be marked "noreturn"
243    bool isTemplateInstantiation = false;
244    if (const FunctionDecl *Function = dyn_cast<FunctionDecl>(Func))
245      isTemplateInstantiation = Function->isTemplateInstantiation();
246
247    if (!isVirtualMethod && !isTemplateInstantiation)
248      D.diag_NeverFallThroughOrReturn =
249        diag::warn_suggest_noreturn_function;
250    else
251      D.diag_NeverFallThroughOrReturn = 0;
252
253    D.funMode = Function;
254    return D;
255  }
256
257  static CheckFallThroughDiagnostics MakeForBlock() {
258    CheckFallThroughDiagnostics D;
259    D.diag_MaybeFallThrough_HasNoReturn =
260      diag::err_noreturn_block_has_return_expr;
261    D.diag_MaybeFallThrough_ReturnsNonVoid =
262      diag::err_maybe_falloff_nonvoid_block;
263    D.diag_AlwaysFallThrough_HasNoReturn =
264      diag::err_noreturn_block_has_return_expr;
265    D.diag_AlwaysFallThrough_ReturnsNonVoid =
266      diag::err_falloff_nonvoid_block;
267    D.diag_NeverFallThroughOrReturn =
268      diag::warn_suggest_noreturn_block;
269    D.funMode = Block;
270    return D;
271  }
272
273  static CheckFallThroughDiagnostics MakeForLambda() {
274    CheckFallThroughDiagnostics D;
275    D.diag_MaybeFallThrough_HasNoReturn =
276      diag::err_noreturn_lambda_has_return_expr;
277    D.diag_MaybeFallThrough_ReturnsNonVoid =
278      diag::warn_maybe_falloff_nonvoid_lambda;
279    D.diag_AlwaysFallThrough_HasNoReturn =
280      diag::err_noreturn_lambda_has_return_expr;
281    D.diag_AlwaysFallThrough_ReturnsNonVoid =
282      diag::warn_falloff_nonvoid_lambda;
283    D.diag_NeverFallThroughOrReturn = 0;
284    D.funMode = Lambda;
285    return D;
286  }
287
288  bool checkDiagnostics(DiagnosticsEngine &D, bool ReturnsVoid,
289                        bool HasNoReturn) const {
290    if (funMode == Function) {
291      return (ReturnsVoid ||
292              D.getDiagnosticLevel(diag::warn_maybe_falloff_nonvoid_function,
293                                   FuncLoc) == DiagnosticsEngine::Ignored)
294        && (!HasNoReturn ||
295            D.getDiagnosticLevel(diag::warn_noreturn_function_has_return_expr,
296                                 FuncLoc) == DiagnosticsEngine::Ignored)
297        && (!ReturnsVoid ||
298            D.getDiagnosticLevel(diag::warn_suggest_noreturn_block, FuncLoc)
299              == DiagnosticsEngine::Ignored);
300    }
301
302    // For blocks / lambdas.
303    return ReturnsVoid && !HasNoReturn
304            && ((funMode == Lambda) ||
305                D.getDiagnosticLevel(diag::warn_suggest_noreturn_block, FuncLoc)
306                  == DiagnosticsEngine::Ignored);
307  }
308};
309
310}
311
312/// CheckFallThroughForFunctionDef - Check that we don't fall off the end of a
313/// function that should return a value.  Check that we don't fall off the end
314/// of a noreturn function.  We assume that functions and blocks not marked
315/// noreturn will return.
316static void CheckFallThroughForBody(Sema &S, const Decl *D, const Stmt *Body,
317                                    const BlockExpr *blkExpr,
318                                    const CheckFallThroughDiagnostics& CD,
319                                    AnalysisDeclContext &AC) {
320
321  bool ReturnsVoid = false;
322  bool HasNoReturn = false;
323
324  if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
325    ReturnsVoid = FD->getResultType()->isVoidType();
326    HasNoReturn = FD->hasAttr<NoReturnAttr>() ||
327       FD->getType()->getAs<FunctionType>()->getNoReturnAttr();
328  }
329  else if (const ObjCMethodDecl *MD = dyn_cast<ObjCMethodDecl>(D)) {
330    ReturnsVoid = MD->getResultType()->isVoidType();
331    HasNoReturn = MD->hasAttr<NoReturnAttr>();
332  }
333  else if (isa<BlockDecl>(D)) {
334    QualType BlockTy = blkExpr->getType();
335    if (const FunctionType *FT =
336          BlockTy->getPointeeType()->getAs<FunctionType>()) {
337      if (FT->getResultType()->isVoidType())
338        ReturnsVoid = true;
339      if (FT->getNoReturnAttr())
340        HasNoReturn = true;
341    }
342  }
343
344  DiagnosticsEngine &Diags = S.getDiagnostics();
345
346  // Short circuit for compilation speed.
347  if (CD.checkDiagnostics(Diags, ReturnsVoid, HasNoReturn))
348      return;
349
350  // FIXME: Function try block
351  if (const CompoundStmt *Compound = dyn_cast<CompoundStmt>(Body)) {
352    switch (CheckFallThrough(AC)) {
353      case UnknownFallThrough:
354        break;
355
356      case MaybeFallThrough:
357        if (HasNoReturn)
358          S.Diag(Compound->getRBracLoc(),
359                 CD.diag_MaybeFallThrough_HasNoReturn);
360        else if (!ReturnsVoid)
361          S.Diag(Compound->getRBracLoc(),
362                 CD.diag_MaybeFallThrough_ReturnsNonVoid);
363        break;
364      case AlwaysFallThrough:
365        if (HasNoReturn)
366          S.Diag(Compound->getRBracLoc(),
367                 CD.diag_AlwaysFallThrough_HasNoReturn);
368        else if (!ReturnsVoid)
369          S.Diag(Compound->getRBracLoc(),
370                 CD.diag_AlwaysFallThrough_ReturnsNonVoid);
371        break;
372      case NeverFallThroughOrReturn:
373        if (ReturnsVoid && !HasNoReturn && CD.diag_NeverFallThroughOrReturn) {
374          if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
375            S.Diag(Compound->getLBracLoc(), CD.diag_NeverFallThroughOrReturn)
376              << 0 << FD;
377          } else if (const ObjCMethodDecl *MD = dyn_cast<ObjCMethodDecl>(D)) {
378            S.Diag(Compound->getLBracLoc(), CD.diag_NeverFallThroughOrReturn)
379              << 1 << MD;
380          } else {
381            S.Diag(Compound->getLBracLoc(), CD.diag_NeverFallThroughOrReturn);
382          }
383        }
384        break;
385      case NeverFallThrough:
386        break;
387    }
388  }
389}
390
391//===----------------------------------------------------------------------===//
392// -Wuninitialized
393//===----------------------------------------------------------------------===//
394
395namespace {
396/// ContainsReference - A visitor class to search for references to
397/// a particular declaration (the needle) within any evaluated component of an
398/// expression (recursively).
399class ContainsReference : public EvaluatedExprVisitor<ContainsReference> {
400  bool FoundReference;
401  const DeclRefExpr *Needle;
402
403public:
404  ContainsReference(ASTContext &Context, const DeclRefExpr *Needle)
405    : EvaluatedExprVisitor<ContainsReference>(Context),
406      FoundReference(false), Needle(Needle) {}
407
408  void VisitExpr(Expr *E) {
409    // Stop evaluating if we already have a reference.
410    if (FoundReference)
411      return;
412
413    EvaluatedExprVisitor<ContainsReference>::VisitExpr(E);
414  }
415
416  void VisitDeclRefExpr(DeclRefExpr *E) {
417    if (E == Needle)
418      FoundReference = true;
419    else
420      EvaluatedExprVisitor<ContainsReference>::VisitDeclRefExpr(E);
421  }
422
423  bool doesContainReference() const { return FoundReference; }
424};
425}
426
427static bool SuggestInitializationFixit(Sema &S, const VarDecl *VD) {
428  // Don't issue a fixit if there is already an initializer.
429  if (VD->getInit())
430    return false;
431
432  // Suggest possible initialization (if any).
433  QualType VariableTy = VD->getType().getCanonicalType();
434  const char *Init = S.getFixItZeroInitializerForType(VariableTy);
435  if (!Init)
436    return false;
437
438  SourceLocation Loc = S.PP.getLocForEndOfToken(VD->getLocEnd());
439  S.Diag(Loc, diag::note_var_fixit_add_initialization) << VD->getDeclName()
440    << FixItHint::CreateInsertion(Loc, Init);
441  return true;
442}
443
444/// DiagnoseUninitializedUse -- Helper function for diagnosing uses of an
445/// uninitialized variable. This manages the different forms of diagnostic
446/// emitted for particular types of uses. Returns true if the use was diagnosed
447/// as a warning. If a pariticular use is one we omit warnings for, returns
448/// false.
449static bool DiagnoseUninitializedUse(Sema &S, const VarDecl *VD,
450                                     const Expr *E, bool isAlwaysUninit,
451                                     bool alwaysReportSelfInit = false) {
452  bool isSelfInit = false;
453
454  if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E)) {
455    if (isAlwaysUninit) {
456      // Inspect the initializer of the variable declaration which is
457      // being referenced prior to its initialization. We emit
458      // specialized diagnostics for self-initialization, and we
459      // specifically avoid warning about self references which take the
460      // form of:
461      //
462      //   int x = x;
463      //
464      // This is used to indicate to GCC that 'x' is intentionally left
465      // uninitialized. Proven code paths which access 'x' in
466      // an uninitialized state after this will still warn.
467      //
468      // TODO: Should we suppress maybe-uninitialized warnings for
469      // variables initialized in this way?
470      if (const Expr *Initializer = VD->getInit()) {
471        if (!alwaysReportSelfInit && DRE == Initializer->IgnoreParenImpCasts())
472          return false;
473
474        ContainsReference CR(S.Context, DRE);
475        CR.Visit(const_cast<Expr*>(Initializer));
476        isSelfInit = CR.doesContainReference();
477      }
478      if (isSelfInit) {
479        S.Diag(DRE->getLocStart(),
480               diag::warn_uninit_self_reference_in_init)
481        << VD->getDeclName() << VD->getLocation() << DRE->getSourceRange();
482      } else {
483        S.Diag(DRE->getLocStart(), diag::warn_uninit_var)
484          << VD->getDeclName() << DRE->getSourceRange();
485      }
486    } else {
487      S.Diag(DRE->getLocStart(), diag::warn_maybe_uninit_var)
488        << VD->getDeclName() << DRE->getSourceRange();
489    }
490  } else {
491    const BlockExpr *BE = cast<BlockExpr>(E);
492    S.Diag(BE->getLocStart(),
493           isAlwaysUninit ? diag::warn_uninit_var_captured_by_block
494                          : diag::warn_maybe_uninit_var_captured_by_block)
495      << VD->getDeclName();
496  }
497
498  // Report where the variable was declared when the use wasn't within
499  // the initializer of that declaration & we didn't already suggest
500  // an initialization fixit.
501  if (!isSelfInit && !SuggestInitializationFixit(S, VD))
502    S.Diag(VD->getLocStart(), diag::note_uninit_var_def)
503      << VD->getDeclName();
504
505  return true;
506}
507
508typedef std::pair<const Expr*, bool> UninitUse;
509
510namespace {
511struct SLocSort {
512  bool operator()(const UninitUse &a, const UninitUse &b) {
513    SourceLocation aLoc = a.first->getLocStart();
514    SourceLocation bLoc = b.first->getLocStart();
515    return aLoc.getRawEncoding() < bLoc.getRawEncoding();
516  }
517};
518
519class UninitValsDiagReporter : public UninitVariablesHandler {
520  Sema &S;
521  typedef SmallVector<UninitUse, 2> UsesVec;
522  typedef llvm::DenseMap<const VarDecl *, std::pair<UsesVec*, bool> > UsesMap;
523  UsesMap *uses;
524
525public:
526  UninitValsDiagReporter(Sema &S) : S(S), uses(0) {}
527  ~UninitValsDiagReporter() {
528    flushDiagnostics();
529  }
530
531  std::pair<UsesVec*, bool> &getUses(const VarDecl *vd) {
532    if (!uses)
533      uses = new UsesMap();
534
535    UsesMap::mapped_type &V = (*uses)[vd];
536    UsesVec *&vec = V.first;
537    if (!vec)
538      vec = new UsesVec();
539
540    return V;
541  }
542
543  void handleUseOfUninitVariable(const Expr *ex, const VarDecl *vd,
544                                 bool isAlwaysUninit) {
545    getUses(vd).first->push_back(std::make_pair(ex, isAlwaysUninit));
546  }
547
548  void handleSelfInit(const VarDecl *vd) {
549    getUses(vd).second = true;
550  }
551
552  void flushDiagnostics() {
553    if (!uses)
554      return;
555
556    for (UsesMap::iterator i = uses->begin(), e = uses->end(); i != e; ++i) {
557      const VarDecl *vd = i->first;
558      const UsesMap::mapped_type &V = i->second;
559
560      UsesVec *vec = V.first;
561      bool hasSelfInit = V.second;
562
563      // Specially handle the case where we have uses of an uninitialized
564      // variable, but the root cause is an idiomatic self-init.  We want
565      // to report the diagnostic at the self-init since that is the root cause.
566      if (!vec->empty() && hasSelfInit && hasAlwaysUninitializedUse(vec))
567        DiagnoseUninitializedUse(S, vd, vd->getInit()->IgnoreParenCasts(),
568                                 /* isAlwaysUninit */ true,
569                                 /* alwaysReportSelfInit */ true);
570      else {
571        // Sort the uses by their SourceLocations.  While not strictly
572        // guaranteed to produce them in line/column order, this will provide
573        // a stable ordering.
574        std::sort(vec->begin(), vec->end(), SLocSort());
575
576        for (UsesVec::iterator vi = vec->begin(), ve = vec->end(); vi != ve;
577             ++vi) {
578          if (DiagnoseUninitializedUse(S, vd, vi->first,
579                                        /*isAlwaysUninit=*/vi->second))
580            // Skip further diagnostics for this variable. We try to warn only
581            // on the first point at which a variable is used uninitialized.
582            break;
583        }
584      }
585
586      // Release the uses vector.
587      delete vec;
588    }
589    delete uses;
590  }
591
592private:
593  static bool hasAlwaysUninitializedUse(const UsesVec* vec) {
594  for (UsesVec::const_iterator i = vec->begin(), e = vec->end(); i != e; ++i) {
595    if (i->second) {
596      return true;
597    }
598  }
599  return false;
600}
601};
602}
603
604
605//===----------------------------------------------------------------------===//
606// -Wthread-safety
607//===----------------------------------------------------------------------===//
608namespace clang {
609namespace thread_safety {
610typedef llvm::SmallVector<PartialDiagnosticAt, 1> OptionalNotes;
611typedef std::pair<PartialDiagnosticAt, OptionalNotes> DelayedDiag;
612typedef llvm::SmallVector<DelayedDiag, 4> DiagList;
613
614struct SortDiagBySourceLocation {
615  Sema &S;
616  SortDiagBySourceLocation(Sema &S) : S(S) {}
617
618  bool operator()(const DelayedDiag &left, const DelayedDiag &right) {
619    // Although this call will be slow, this is only called when outputting
620    // multiple warnings.
621    return S.getSourceManager().isBeforeInTranslationUnit(left.first.first,
622                                                          right.first.first);
623  }
624};
625
626namespace {
627class ThreadSafetyReporter : public clang::thread_safety::ThreadSafetyHandler {
628  Sema &S;
629  DiagList Warnings;
630  SourceLocation FunLocation, FunEndLocation;
631
632  // Helper functions
633  void warnLockMismatch(unsigned DiagID, Name LockName, SourceLocation Loc) {
634    // Gracefully handle rare cases when the analysis can't get a more
635    // precise source location.
636    if (!Loc.isValid())
637      Loc = FunLocation;
638    PartialDiagnosticAt Warning(Loc, S.PDiag(DiagID) << LockName);
639    Warnings.push_back(DelayedDiag(Warning, OptionalNotes()));
640  }
641
642 public:
643  ThreadSafetyReporter(Sema &S, SourceLocation FL, SourceLocation FEL)
644    : S(S), FunLocation(FL), FunEndLocation(FEL) {}
645
646  /// \brief Emit all buffered diagnostics in order of sourcelocation.
647  /// We need to output diagnostics produced while iterating through
648  /// the lockset in deterministic order, so this function orders diagnostics
649  /// and outputs them.
650  void emitDiagnostics() {
651    SortDiagBySourceLocation SortDiagBySL(S);
652    sort(Warnings.begin(), Warnings.end(), SortDiagBySL);
653    for (DiagList::iterator I = Warnings.begin(), E = Warnings.end();
654         I != E; ++I) {
655      S.Diag(I->first.first, I->first.second);
656      const OptionalNotes &Notes = I->second;
657      for (unsigned NoteI = 0, NoteN = Notes.size(); NoteI != NoteN; ++NoteI)
658        S.Diag(Notes[NoteI].first, Notes[NoteI].second);
659    }
660  }
661
662  void handleInvalidLockExp(SourceLocation Loc) {
663    PartialDiagnosticAt Warning(Loc,
664                                S.PDiag(diag::warn_cannot_resolve_lock) << Loc);
665    Warnings.push_back(DelayedDiag(Warning, OptionalNotes()));
666  }
667  void handleUnmatchedUnlock(Name LockName, SourceLocation Loc) {
668    warnLockMismatch(diag::warn_unlock_but_no_lock, LockName, Loc);
669  }
670
671  void handleDoubleLock(Name LockName, SourceLocation Loc) {
672    warnLockMismatch(diag::warn_double_lock, LockName, Loc);
673  }
674
675  void handleMutexHeldEndOfScope(Name LockName, SourceLocation LocLocked,
676                                 SourceLocation LocEndOfScope,
677                                 LockErrorKind LEK){
678    unsigned DiagID = 0;
679    switch (LEK) {
680      case LEK_LockedSomePredecessors:
681        DiagID = diag::warn_lock_some_predecessors;
682        break;
683      case LEK_LockedSomeLoopIterations:
684        DiagID = diag::warn_expecting_lock_held_on_loop;
685        break;
686      case LEK_LockedAtEndOfFunction:
687        DiagID = diag::warn_no_unlock;
688        break;
689    }
690    if (LocEndOfScope.isInvalid())
691      LocEndOfScope = FunEndLocation;
692
693    PartialDiagnosticAt Warning(LocEndOfScope, S.PDiag(DiagID) << LockName);
694    PartialDiagnosticAt Note(LocLocked, S.PDiag(diag::note_locked_here));
695    Warnings.push_back(DelayedDiag(Warning, OptionalNotes(1, Note)));
696  }
697
698
699  void handleExclusiveAndShared(Name LockName, SourceLocation Loc1,
700                                SourceLocation Loc2) {
701    PartialDiagnosticAt Warning(
702      Loc1, S.PDiag(diag::warn_lock_exclusive_and_shared) << LockName);
703    PartialDiagnosticAt Note(
704      Loc2, S.PDiag(diag::note_lock_exclusive_and_shared) << LockName);
705    Warnings.push_back(DelayedDiag(Warning, OptionalNotes(1, Note)));
706  }
707
708  void handleNoMutexHeld(const NamedDecl *D, ProtectedOperationKind POK,
709                         AccessKind AK, SourceLocation Loc) {
710    assert((POK == POK_VarAccess || POK == POK_VarDereference)
711             && "Only works for variables");
712    unsigned DiagID = POK == POK_VarAccess?
713                        diag::warn_variable_requires_any_lock:
714                        diag::warn_var_deref_requires_any_lock;
715    PartialDiagnosticAt Warning(Loc, S.PDiag(DiagID)
716      << D->getName() << getLockKindFromAccessKind(AK));
717    Warnings.push_back(DelayedDiag(Warning, OptionalNotes()));
718  }
719
720  void handleMutexNotHeld(const NamedDecl *D, ProtectedOperationKind POK,
721                          Name LockName, LockKind LK, SourceLocation Loc) {
722    unsigned DiagID = 0;
723    switch (POK) {
724      case POK_VarAccess:
725        DiagID = diag::warn_variable_requires_lock;
726        break;
727      case POK_VarDereference:
728        DiagID = diag::warn_var_deref_requires_lock;
729        break;
730      case POK_FunctionCall:
731        DiagID = diag::warn_fun_requires_lock;
732        break;
733    }
734    PartialDiagnosticAt Warning(Loc, S.PDiag(DiagID)
735      << D->getName() << LockName << LK);
736    Warnings.push_back(DelayedDiag(Warning, OptionalNotes()));
737  }
738
739  void handleFunExcludesLock(Name FunName, Name LockName, SourceLocation Loc) {
740    PartialDiagnosticAt Warning(Loc,
741      S.PDiag(diag::warn_fun_excludes_mutex) << FunName << LockName);
742    Warnings.push_back(DelayedDiag(Warning, OptionalNotes()));
743  }
744};
745}
746}
747}
748
749//===----------------------------------------------------------------------===//
750// AnalysisBasedWarnings - Worker object used by Sema to execute analysis-based
751//  warnings on a function, method, or block.
752//===----------------------------------------------------------------------===//
753
754clang::sema::AnalysisBasedWarnings::Policy::Policy() {
755  enableCheckFallThrough = 1;
756  enableCheckUnreachable = 0;
757  enableThreadSafetyAnalysis = 0;
758}
759
760clang::sema::AnalysisBasedWarnings::AnalysisBasedWarnings(Sema &s)
761  : S(s),
762    NumFunctionsAnalyzed(0),
763    NumFunctionsWithBadCFGs(0),
764    NumCFGBlocks(0),
765    MaxCFGBlocksPerFunction(0),
766    NumUninitAnalysisFunctions(0),
767    NumUninitAnalysisVariables(0),
768    MaxUninitAnalysisVariablesPerFunction(0),
769    NumUninitAnalysisBlockVisits(0),
770    MaxUninitAnalysisBlockVisitsPerFunction(0) {
771  DiagnosticsEngine &D = S.getDiagnostics();
772  DefaultPolicy.enableCheckUnreachable = (unsigned)
773    (D.getDiagnosticLevel(diag::warn_unreachable, SourceLocation()) !=
774        DiagnosticsEngine::Ignored);
775  DefaultPolicy.enableThreadSafetyAnalysis = (unsigned)
776    (D.getDiagnosticLevel(diag::warn_double_lock, SourceLocation()) !=
777     DiagnosticsEngine::Ignored);
778
779}
780
781static void flushDiagnostics(Sema &S, sema::FunctionScopeInfo *fscope) {
782  for (SmallVectorImpl<sema::PossiblyUnreachableDiag>::iterator
783       i = fscope->PossiblyUnreachableDiags.begin(),
784       e = fscope->PossiblyUnreachableDiags.end();
785       i != e; ++i) {
786    const sema::PossiblyUnreachableDiag &D = *i;
787    S.Diag(D.Loc, D.PD);
788  }
789}
790
791void clang::sema::
792AnalysisBasedWarnings::IssueWarnings(sema::AnalysisBasedWarnings::Policy P,
793                                     sema::FunctionScopeInfo *fscope,
794                                     const Decl *D, const BlockExpr *blkExpr) {
795
796  // We avoid doing analysis-based warnings when there are errors for
797  // two reasons:
798  // (1) The CFGs often can't be constructed (if the body is invalid), so
799  //     don't bother trying.
800  // (2) The code already has problems; running the analysis just takes more
801  //     time.
802  DiagnosticsEngine &Diags = S.getDiagnostics();
803
804  // Do not do any analysis for declarations in system headers if we are
805  // going to just ignore them.
806  if (Diags.getSuppressSystemWarnings() &&
807      S.SourceMgr.isInSystemHeader(D->getLocation()))
808    return;
809
810  // For code in dependent contexts, we'll do this at instantiation time.
811  if (cast<DeclContext>(D)->isDependentContext())
812    return;
813
814  if (Diags.hasErrorOccurred() || Diags.hasFatalErrorOccurred()) {
815    // Flush out any possibly unreachable diagnostics.
816    flushDiagnostics(S, fscope);
817    return;
818  }
819
820  const Stmt *Body = D->getBody();
821  assert(Body);
822
823  AnalysisDeclContext AC(/* AnalysisDeclContextManager */ 0,  D, 0);
824
825  // Don't generate EH edges for CallExprs as we'd like to avoid the n^2
826  // explosion for destrutors that can result and the compile time hit.
827  AC.getCFGBuildOptions().PruneTriviallyFalseEdges = true;
828  AC.getCFGBuildOptions().AddEHEdges = false;
829  AC.getCFGBuildOptions().AddInitializers = true;
830  AC.getCFGBuildOptions().AddImplicitDtors = true;
831
832  // Force that certain expressions appear as CFGElements in the CFG.  This
833  // is used to speed up various analyses.
834  // FIXME: This isn't the right factoring.  This is here for initial
835  // prototyping, but we need a way for analyses to say what expressions they
836  // expect to always be CFGElements and then fill in the BuildOptions
837  // appropriately.  This is essentially a layering violation.
838  if (P.enableCheckUnreachable || P.enableThreadSafetyAnalysis) {
839    // Unreachable code analysis and thread safety require a linearized CFG.
840    AC.getCFGBuildOptions().setAllAlwaysAdd();
841  }
842  else {
843    AC.getCFGBuildOptions()
844      .setAlwaysAdd(Stmt::BinaryOperatorClass)
845      .setAlwaysAdd(Stmt::BlockExprClass)
846      .setAlwaysAdd(Stmt::CStyleCastExprClass)
847      .setAlwaysAdd(Stmt::DeclRefExprClass)
848      .setAlwaysAdd(Stmt::ImplicitCastExprClass)
849      .setAlwaysAdd(Stmt::UnaryOperatorClass);
850  }
851
852  // Construct the analysis context with the specified CFG build options.
853
854  // Emit delayed diagnostics.
855  if (!fscope->PossiblyUnreachableDiags.empty()) {
856    bool analyzed = false;
857
858    // Register the expressions with the CFGBuilder.
859    for (SmallVectorImpl<sema::PossiblyUnreachableDiag>::iterator
860         i = fscope->PossiblyUnreachableDiags.begin(),
861         e = fscope->PossiblyUnreachableDiags.end();
862         i != e; ++i) {
863      if (const Stmt *stmt = i->stmt)
864        AC.registerForcedBlockExpression(stmt);
865    }
866
867    if (AC.getCFG()) {
868      analyzed = true;
869      for (SmallVectorImpl<sema::PossiblyUnreachableDiag>::iterator
870            i = fscope->PossiblyUnreachableDiags.begin(),
871            e = fscope->PossiblyUnreachableDiags.end();
872            i != e; ++i)
873      {
874        const sema::PossiblyUnreachableDiag &D = *i;
875        bool processed = false;
876        if (const Stmt *stmt = i->stmt) {
877          const CFGBlock *block = AC.getBlockForRegisteredExpression(stmt);
878          CFGReverseBlockReachabilityAnalysis *cra =
879              AC.getCFGReachablityAnalysis();
880          // FIXME: We should be able to assert that block is non-null, but
881          // the CFG analysis can skip potentially-evaluated expressions in
882          // edge cases; see test/Sema/vla-2.c.
883          if (block && cra) {
884            // Can this block be reached from the entrance?
885            if (cra->isReachable(&AC.getCFG()->getEntry(), block))
886              S.Diag(D.Loc, D.PD);
887            processed = true;
888          }
889        }
890        if (!processed) {
891          // Emit the warning anyway if we cannot map to a basic block.
892          S.Diag(D.Loc, D.PD);
893        }
894      }
895    }
896
897    if (!analyzed)
898      flushDiagnostics(S, fscope);
899  }
900
901
902  // Warning: check missing 'return'
903  if (P.enableCheckFallThrough) {
904    const CheckFallThroughDiagnostics &CD =
905      (isa<BlockDecl>(D) ? CheckFallThroughDiagnostics::MakeForBlock()
906       : (isa<CXXMethodDecl>(D) &&
907          cast<CXXMethodDecl>(D)->getOverloadedOperator() == OO_Call &&
908          cast<CXXMethodDecl>(D)->getParent()->isLambda())
909            ? CheckFallThroughDiagnostics::MakeForLambda()
910            : CheckFallThroughDiagnostics::MakeForFunction(D));
911    CheckFallThroughForBody(S, D, Body, blkExpr, CD, AC);
912  }
913
914  // Warning: check for unreachable code
915  if (P.enableCheckUnreachable) {
916    // Only check for unreachable code on non-template instantiations.
917    // Different template instantiations can effectively change the control-flow
918    // and it is very difficult to prove that a snippet of code in a template
919    // is unreachable for all instantiations.
920    bool isTemplateInstantiation = false;
921    if (const FunctionDecl *Function = dyn_cast<FunctionDecl>(D))
922      isTemplateInstantiation = Function->isTemplateInstantiation();
923    if (!isTemplateInstantiation)
924      CheckUnreachable(S, AC);
925  }
926
927  // Check for thread safety violations
928  if (P.enableThreadSafetyAnalysis) {
929    SourceLocation FL = AC.getDecl()->getLocation();
930    SourceLocation FEL = AC.getDecl()->getLocEnd();
931    thread_safety::ThreadSafetyReporter Reporter(S, FL, FEL);
932    thread_safety::runThreadSafetyAnalysis(AC, Reporter);
933    Reporter.emitDiagnostics();
934  }
935
936  if (Diags.getDiagnosticLevel(diag::warn_uninit_var, D->getLocStart())
937      != DiagnosticsEngine::Ignored ||
938      Diags.getDiagnosticLevel(diag::warn_maybe_uninit_var, D->getLocStart())
939      != DiagnosticsEngine::Ignored) {
940    if (CFG *cfg = AC.getCFG()) {
941      UninitValsDiagReporter reporter(S);
942      UninitVariablesAnalysisStats stats;
943      std::memset(&stats, 0, sizeof(UninitVariablesAnalysisStats));
944      runUninitializedVariablesAnalysis(*cast<DeclContext>(D), *cfg, AC,
945                                        reporter, stats);
946
947      if (S.CollectStats && stats.NumVariablesAnalyzed > 0) {
948        ++NumUninitAnalysisFunctions;
949        NumUninitAnalysisVariables += stats.NumVariablesAnalyzed;
950        NumUninitAnalysisBlockVisits += stats.NumBlockVisits;
951        MaxUninitAnalysisVariablesPerFunction =
952            std::max(MaxUninitAnalysisVariablesPerFunction,
953                     stats.NumVariablesAnalyzed);
954        MaxUninitAnalysisBlockVisitsPerFunction =
955            std::max(MaxUninitAnalysisBlockVisitsPerFunction,
956                     stats.NumBlockVisits);
957      }
958    }
959  }
960
961  // Collect statistics about the CFG if it was built.
962  if (S.CollectStats && AC.isCFGBuilt()) {
963    ++NumFunctionsAnalyzed;
964    if (CFG *cfg = AC.getCFG()) {
965      // If we successfully built a CFG for this context, record some more
966      // detail information about it.
967      NumCFGBlocks += cfg->getNumBlockIDs();
968      MaxCFGBlocksPerFunction = std::max(MaxCFGBlocksPerFunction,
969                                         cfg->getNumBlockIDs());
970    } else {
971      ++NumFunctionsWithBadCFGs;
972    }
973  }
974}
975
976void clang::sema::AnalysisBasedWarnings::PrintStats() const {
977  llvm::errs() << "\n*** Analysis Based Warnings Stats:\n";
978
979  unsigned NumCFGsBuilt = NumFunctionsAnalyzed - NumFunctionsWithBadCFGs;
980  unsigned AvgCFGBlocksPerFunction =
981      !NumCFGsBuilt ? 0 : NumCFGBlocks/NumCFGsBuilt;
982  llvm::errs() << NumFunctionsAnalyzed << " functions analyzed ("
983               << NumFunctionsWithBadCFGs << " w/o CFGs).\n"
984               << "  " << NumCFGBlocks << " CFG blocks built.\n"
985               << "  " << AvgCFGBlocksPerFunction
986               << " average CFG blocks per function.\n"
987               << "  " << MaxCFGBlocksPerFunction
988               << " max CFG blocks per function.\n";
989
990  unsigned AvgUninitVariablesPerFunction = !NumUninitAnalysisFunctions ? 0
991      : NumUninitAnalysisVariables/NumUninitAnalysisFunctions;
992  unsigned AvgUninitBlockVisitsPerFunction = !NumUninitAnalysisFunctions ? 0
993      : NumUninitAnalysisBlockVisits/NumUninitAnalysisFunctions;
994  llvm::errs() << NumUninitAnalysisFunctions
995               << " functions analyzed for uninitialiazed variables\n"
996               << "  " << NumUninitAnalysisVariables << " variables analyzed.\n"
997               << "  " << AvgUninitVariablesPerFunction
998               << " average variables per function.\n"
999               << "  " << MaxUninitAnalysisVariablesPerFunction
1000               << " max variables per function.\n"
1001               << "  " << NumUninitAnalysisBlockVisits << " block visits.\n"
1002               << "  " << AvgUninitBlockVisitsPerFunction
1003               << " average block visits per function.\n"
1004               << "  " << MaxUninitAnalysisBlockVisitsPerFunction
1005               << " max block visits per function.\n";
1006}
1007