AnalysisBasedWarnings.cpp revision 2e5156274b8051217565b557bfa14c80f7990e9c 
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  bool 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 = true;
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 = false;
270    return D;
271  }
272
273  bool checkDiagnostics(DiagnosticsEngine &D, bool ReturnsVoid,
274                        bool HasNoReturn) const {
275    if (funMode) {
276      return (ReturnsVoid ||
277              D.getDiagnosticLevel(diag::warn_maybe_falloff_nonvoid_function,
278                                   FuncLoc) == DiagnosticsEngine::Ignored)
279        && (!HasNoReturn ||
280            D.getDiagnosticLevel(diag::warn_noreturn_function_has_return_expr,
281                                 FuncLoc) == DiagnosticsEngine::Ignored)
282        && (!ReturnsVoid ||
283            D.getDiagnosticLevel(diag::warn_suggest_noreturn_block, FuncLoc)
284              == DiagnosticsEngine::Ignored);
285    }
286
287    // For blocks.
288    return  ReturnsVoid && !HasNoReturn
289            && (!ReturnsVoid ||
290                D.getDiagnosticLevel(diag::warn_suggest_noreturn_block, FuncLoc)
291                  == DiagnosticsEngine::Ignored);
292  }
293};
294
295}
296
297/// CheckFallThroughForFunctionDef - Check that we don't fall off the end of a
298/// function that should return a value.  Check that we don't fall off the end
299/// of a noreturn function.  We assume that functions and blocks not marked
300/// noreturn will return.
301static void CheckFallThroughForBody(Sema &S, const Decl *D, const Stmt *Body,
302                                    const BlockExpr *blkExpr,
303                                    const CheckFallThroughDiagnostics& CD,
304                                    AnalysisDeclContext &AC) {
305
306  bool ReturnsVoid = false;
307  bool HasNoReturn = false;
308
309  if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
310    ReturnsVoid = FD->getResultType()->isVoidType();
311    HasNoReturn = FD->hasAttr<NoReturnAttr>() ||
312       FD->getType()->getAs<FunctionType>()->getNoReturnAttr();
313  }
314  else if (const ObjCMethodDecl *MD = dyn_cast<ObjCMethodDecl>(D)) {
315    ReturnsVoid = MD->getResultType()->isVoidType();
316    HasNoReturn = MD->hasAttr<NoReturnAttr>();
317  }
318  else if (isa<BlockDecl>(D)) {
319    QualType BlockTy = blkExpr->getType();
320    if (const FunctionType *FT =
321          BlockTy->getPointeeType()->getAs<FunctionType>()) {
322      if (FT->getResultType()->isVoidType())
323        ReturnsVoid = true;
324      if (FT->getNoReturnAttr())
325        HasNoReturn = true;
326    }
327  }
328
329  DiagnosticsEngine &Diags = S.getDiagnostics();
330
331  // Short circuit for compilation speed.
332  if (CD.checkDiagnostics(Diags, ReturnsVoid, HasNoReturn))
333      return;
334
335  // FIXME: Function try block
336  if (const CompoundStmt *Compound = dyn_cast<CompoundStmt>(Body)) {
337    switch (CheckFallThrough(AC)) {
338      case UnknownFallThrough:
339        break;
340
341      case MaybeFallThrough:
342        if (HasNoReturn)
343          S.Diag(Compound->getRBracLoc(),
344                 CD.diag_MaybeFallThrough_HasNoReturn);
345        else if (!ReturnsVoid)
346          S.Diag(Compound->getRBracLoc(),
347                 CD.diag_MaybeFallThrough_ReturnsNonVoid);
348        break;
349      case AlwaysFallThrough:
350        if (HasNoReturn)
351          S.Diag(Compound->getRBracLoc(),
352                 CD.diag_AlwaysFallThrough_HasNoReturn);
353        else if (!ReturnsVoid)
354          S.Diag(Compound->getRBracLoc(),
355                 CD.diag_AlwaysFallThrough_ReturnsNonVoid);
356        break;
357      case NeverFallThroughOrReturn:
358        if (ReturnsVoid && !HasNoReturn && CD.diag_NeverFallThroughOrReturn) {
359          if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
360            S.Diag(Compound->getLBracLoc(), CD.diag_NeverFallThroughOrReturn)
361              << 0 << FD;
362          } else if (const ObjCMethodDecl *MD = dyn_cast<ObjCMethodDecl>(D)) {
363            S.Diag(Compound->getLBracLoc(), CD.diag_NeverFallThroughOrReturn)
364              << 1 << MD;
365          } else {
366            S.Diag(Compound->getLBracLoc(), CD.diag_NeverFallThroughOrReturn);
367          }
368        }
369        break;
370      case NeverFallThrough:
371        break;
372    }
373  }
374}
375
376//===----------------------------------------------------------------------===//
377// -Wuninitialized
378//===----------------------------------------------------------------------===//
379
380namespace {
381/// ContainsReference - A visitor class to search for references to
382/// a particular declaration (the needle) within any evaluated component of an
383/// expression (recursively).
384class ContainsReference : public EvaluatedExprVisitor<ContainsReference> {
385  bool FoundReference;
386  const DeclRefExpr *Needle;
387
388public:
389  ContainsReference(ASTContext &Context, const DeclRefExpr *Needle)
390    : EvaluatedExprVisitor<ContainsReference>(Context),
391      FoundReference(false), Needle(Needle) {}
392
393  void VisitExpr(Expr *E) {
394    // Stop evaluating if we already have a reference.
395    if (FoundReference)
396      return;
397
398    EvaluatedExprVisitor<ContainsReference>::VisitExpr(E);
399  }
400
401  void VisitDeclRefExpr(DeclRefExpr *E) {
402    if (E == Needle)
403      FoundReference = true;
404    else
405      EvaluatedExprVisitor<ContainsReference>::VisitDeclRefExpr(E);
406  }
407
408  bool doesContainReference() const { return FoundReference; }
409};
410}
411
412static bool SuggestInitializationFixit(Sema &S, const VarDecl *VD) {
413  // Don't issue a fixit if there is already an initializer.
414  if (VD->getInit())
415    return false;
416
417  // Suggest possible initialization (if any).
418  QualType VariableTy = VD->getType().getCanonicalType();
419  const char *Init = S.getFixItZeroInitializerForType(VariableTy);
420  if (!Init)
421    return false;
422
423  SourceLocation Loc = S.PP.getLocForEndOfToken(VD->getLocEnd());
424  S.Diag(Loc, diag::note_var_fixit_add_initialization) << VD->getDeclName()
425    << FixItHint::CreateInsertion(Loc, Init);
426  return true;
427}
428
429/// DiagnoseUninitializedUse -- Helper function for diagnosing uses of an
430/// uninitialized variable. This manages the different forms of diagnostic
431/// emitted for particular types of uses. Returns true if the use was diagnosed
432/// as a warning. If a pariticular use is one we omit warnings for, returns
433/// false.
434static bool DiagnoseUninitializedUse(Sema &S, const VarDecl *VD,
435                                     const Expr *E, bool isAlwaysUninit,
436                                     bool alwaysReportSelfInit = false) {
437  bool isSelfInit = false;
438
439  if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E)) {
440    if (isAlwaysUninit) {
441      // Inspect the initializer of the variable declaration which is
442      // being referenced prior to its initialization. We emit
443      // specialized diagnostics for self-initialization, and we
444      // specifically avoid warning about self references which take the
445      // form of:
446      //
447      //   int x = x;
448      //
449      // This is used to indicate to GCC that 'x' is intentionally left
450      // uninitialized. Proven code paths which access 'x' in
451      // an uninitialized state after this will still warn.
452      //
453      // TODO: Should we suppress maybe-uninitialized warnings for
454      // variables initialized in this way?
455      if (const Expr *Initializer = VD->getInit()) {
456        if (!alwaysReportSelfInit && DRE == Initializer->IgnoreParenImpCasts())
457          return false;
458
459        ContainsReference CR(S.Context, DRE);
460        CR.Visit(const_cast<Expr*>(Initializer));
461        isSelfInit = CR.doesContainReference();
462      }
463      if (isSelfInit) {
464        S.Diag(DRE->getLocStart(),
465               diag::warn_uninit_self_reference_in_init)
466        << VD->getDeclName() << VD->getLocation() << DRE->getSourceRange();
467      } else {
468        S.Diag(DRE->getLocStart(), diag::warn_uninit_var)
469          << VD->getDeclName() << DRE->getSourceRange();
470      }
471    } else {
472      S.Diag(DRE->getLocStart(), diag::warn_maybe_uninit_var)
473        << VD->getDeclName() << DRE->getSourceRange();
474    }
475  } else {
476    const BlockExpr *BE = cast<BlockExpr>(E);
477    S.Diag(BE->getLocStart(),
478           isAlwaysUninit ? diag::warn_uninit_var_captured_by_block
479                          : diag::warn_maybe_uninit_var_captured_by_block)
480      << VD->getDeclName();
481  }
482
483  // Report where the variable was declared when the use wasn't within
484  // the initializer of that declaration & we didn't already suggest
485  // an initialization fixit.
486  if (!isSelfInit && !SuggestInitializationFixit(S, VD))
487    S.Diag(VD->getLocStart(), diag::note_uninit_var_def)
488      << VD->getDeclName();
489
490  return true;
491}
492
493typedef std::pair<const Expr*, bool> UninitUse;
494
495namespace {
496struct SLocSort {
497  bool operator()(const UninitUse &a, const UninitUse &b) {
498    SourceLocation aLoc = a.first->getLocStart();
499    SourceLocation bLoc = b.first->getLocStart();
500    return aLoc.getRawEncoding() < bLoc.getRawEncoding();
501  }
502};
503
504class UninitValsDiagReporter : public UninitVariablesHandler {
505  Sema &S;
506  typedef SmallVector<UninitUse, 2> UsesVec;
507  typedef llvm::DenseMap<const VarDecl *, std::pair<UsesVec*, bool> > UsesMap;
508  UsesMap *uses;
509
510public:
511  UninitValsDiagReporter(Sema &S) : S(S), uses(0) {}
512  ~UninitValsDiagReporter() {
513    flushDiagnostics();
514  }
515
516  std::pair<UsesVec*, bool> &getUses(const VarDecl *vd) {
517    if (!uses)
518      uses = new UsesMap();
519
520    UsesMap::mapped_type &V = (*uses)[vd];
521    UsesVec *&vec = V.first;
522    if (!vec)
523      vec = new UsesVec();
524
525    return V;
526  }
527
528  void handleUseOfUninitVariable(const Expr *ex, const VarDecl *vd,
529                                 bool isAlwaysUninit) {
530    getUses(vd).first->push_back(std::make_pair(ex, isAlwaysUninit));
531  }
532
533  void handleSelfInit(const VarDecl *vd) {
534    getUses(vd).second = true;
535  }
536
537  void flushDiagnostics() {
538    if (!uses)
539      return;
540
541    for (UsesMap::iterator i = uses->begin(), e = uses->end(); i != e; ++i) {
542      const VarDecl *vd = i->first;
543      const UsesMap::mapped_type &V = i->second;
544
545      UsesVec *vec = V.first;
546      bool hasSelfInit = V.second;
547
548      // Specially handle the case where we have uses of an uninitialized
549      // variable, but the root cause is an idiomatic self-init.  We want
550      // to report the diagnostic at the self-init since that is the root cause.
551      if (!vec->empty() && hasSelfInit && hasAlwaysUninitializedUse(vec))
552        DiagnoseUninitializedUse(S, vd, vd->getInit()->IgnoreParenCasts(),
553                                 /* isAlwaysUninit */ true,
554                                 /* alwaysReportSelfInit */ true);
555      else {
556        // Sort the uses by their SourceLocations.  While not strictly
557        // guaranteed to produce them in line/column order, this will provide
558        // a stable ordering.
559        std::sort(vec->begin(), vec->end(), SLocSort());
560
561        for (UsesVec::iterator vi = vec->begin(), ve = vec->end(); vi != ve;
562             ++vi) {
563          if (DiagnoseUninitializedUse(S, vd, vi->first,
564                                        /*isAlwaysUninit=*/vi->second))
565            // Skip further diagnostics for this variable. We try to warn only
566            // on the first point at which a variable is used uninitialized.
567            break;
568        }
569      }
570
571      // Release the uses vector.
572      delete vec;
573    }
574    delete uses;
575  }
576
577private:
578  static bool hasAlwaysUninitializedUse(const UsesVec* vec) {
579  for (UsesVec::const_iterator i = vec->begin(), e = vec->end(); i != e; ++i) {
580    if (i->second) {
581      return true;
582    }
583  }
584  return false;
585}
586};
587}
588
589
590//===----------------------------------------------------------------------===//
591// -Wthread-safety
592//===----------------------------------------------------------------------===//
593namespace clang {
594namespace thread_safety {
595typedef llvm::SmallVector<PartialDiagnosticAt, 1> OptionalNotes;
596typedef std::pair<PartialDiagnosticAt, OptionalNotes> DelayedDiag;
597typedef llvm::SmallVector<DelayedDiag, 4> DiagList;
598
599struct SortDiagBySourceLocation {
600  Sema &S;
601  SortDiagBySourceLocation(Sema &S) : S(S) {}
602
603  bool operator()(const DelayedDiag &left, const DelayedDiag &right) {
604    // Although this call will be slow, this is only called when outputting
605    // multiple warnings.
606    return S.getSourceManager().isBeforeInTranslationUnit(left.first.first,
607                                                          right.first.first);
608  }
609};
610
611namespace {
612class ThreadSafetyReporter : public clang::thread_safety::ThreadSafetyHandler {
613  Sema &S;
614  DiagList Warnings;
615  SourceLocation FunLocation, FunEndLocation;
616
617  // Helper functions
618  void warnLockMismatch(unsigned DiagID, Name LockName, SourceLocation Loc) {
619    // Gracefully handle rare cases when the analysis can't get a more
620    // precise source location.
621    if (!Loc.isValid())
622      Loc = FunLocation;
623    PartialDiagnosticAt Warning(Loc, S.PDiag(DiagID) << LockName);
624    Warnings.push_back(DelayedDiag(Warning, OptionalNotes()));
625  }
626
627 public:
628  ThreadSafetyReporter(Sema &S, SourceLocation FL, SourceLocation FEL)
629    : S(S), FunLocation(FL), FunEndLocation(FEL) {}
630
631  /// \brief Emit all buffered diagnostics in order of sourcelocation.
632  /// We need to output diagnostics produced while iterating through
633  /// the lockset in deterministic order, so this function orders diagnostics
634  /// and outputs them.
635  void emitDiagnostics() {
636    SortDiagBySourceLocation SortDiagBySL(S);
637    sort(Warnings.begin(), Warnings.end(), SortDiagBySL);
638    for (DiagList::iterator I = Warnings.begin(), E = Warnings.end();
639         I != E; ++I) {
640      S.Diag(I->first.first, I->first.second);
641      const OptionalNotes &Notes = I->second;
642      for (unsigned NoteI = 0, NoteN = Notes.size(); NoteI != NoteN; ++NoteI)
643        S.Diag(Notes[NoteI].first, Notes[NoteI].second);
644    }
645  }
646
647  void handleInvalidLockExp(SourceLocation Loc) {
648    PartialDiagnosticAt Warning(Loc,
649                                S.PDiag(diag::warn_cannot_resolve_lock) << Loc);
650    Warnings.push_back(DelayedDiag(Warning, OptionalNotes()));
651  }
652  void handleUnmatchedUnlock(Name LockName, SourceLocation Loc) {
653    warnLockMismatch(diag::warn_unlock_but_no_lock, LockName, Loc);
654  }
655
656  void handleDoubleLock(Name LockName, SourceLocation Loc) {
657    warnLockMismatch(diag::warn_double_lock, LockName, Loc);
658  }
659
660  void handleMutexHeldEndOfScope(Name LockName, SourceLocation LocLocked,
661                                 SourceLocation LocEndOfScope,
662                                 LockErrorKind LEK){
663    unsigned DiagID = 0;
664    switch (LEK) {
665      case LEK_LockedSomePredecessors:
666        DiagID = diag::warn_lock_some_predecessors;
667        break;
668      case LEK_LockedSomeLoopIterations:
669        DiagID = diag::warn_expecting_lock_held_on_loop;
670        break;
671      case LEK_LockedAtEndOfFunction:
672        DiagID = diag::warn_no_unlock;
673        break;
674    }
675    if (LocEndOfScope.isInvalid())
676      LocEndOfScope = FunEndLocation;
677
678    PartialDiagnosticAt Warning(LocEndOfScope, S.PDiag(DiagID) << LockName);
679    PartialDiagnosticAt Note(LocLocked, S.PDiag(diag::note_locked_here));
680    Warnings.push_back(DelayedDiag(Warning, OptionalNotes(1, Note)));
681  }
682
683
684  void handleExclusiveAndShared(Name LockName, SourceLocation Loc1,
685                                SourceLocation Loc2) {
686    PartialDiagnosticAt Warning(
687      Loc1, S.PDiag(diag::warn_lock_exclusive_and_shared) << LockName);
688    PartialDiagnosticAt Note(
689      Loc2, S.PDiag(diag::note_lock_exclusive_and_shared) << LockName);
690    Warnings.push_back(DelayedDiag(Warning, OptionalNotes(1, Note)));
691  }
692
693  void handleNoMutexHeld(const NamedDecl *D, ProtectedOperationKind POK,
694                         AccessKind AK, SourceLocation Loc) {
695    assert((POK == POK_VarAccess || POK == POK_VarDereference)
696             && "Only works for variables");
697    unsigned DiagID = POK == POK_VarAccess?
698                        diag::warn_variable_requires_any_lock:
699                        diag::warn_var_deref_requires_any_lock;
700    PartialDiagnosticAt Warning(Loc, S.PDiag(DiagID)
701      << D->getName() << getLockKindFromAccessKind(AK));
702    Warnings.push_back(DelayedDiag(Warning, OptionalNotes()));
703  }
704
705  void handleMutexNotHeld(const NamedDecl *D, ProtectedOperationKind POK,
706                          Name LockName, LockKind LK, SourceLocation Loc) {
707    unsigned DiagID = 0;
708    switch (POK) {
709      case POK_VarAccess:
710        DiagID = diag::warn_variable_requires_lock;
711        break;
712      case POK_VarDereference:
713        DiagID = diag::warn_var_deref_requires_lock;
714        break;
715      case POK_FunctionCall:
716        DiagID = diag::warn_fun_requires_lock;
717        break;
718    }
719    PartialDiagnosticAt Warning(Loc, S.PDiag(DiagID)
720      << D->getName() << LockName << LK);
721    Warnings.push_back(DelayedDiag(Warning, OptionalNotes()));
722  }
723
724  void handleFunExcludesLock(Name FunName, Name LockName, SourceLocation Loc) {
725    PartialDiagnosticAt Warning(Loc,
726      S.PDiag(diag::warn_fun_excludes_mutex) << FunName << LockName);
727    Warnings.push_back(DelayedDiag(Warning, OptionalNotes()));
728  }
729};
730}
731}
732}
733
734//===----------------------------------------------------------------------===//
735// AnalysisBasedWarnings - Worker object used by Sema to execute analysis-based
736//  warnings on a function, method, or block.
737//===----------------------------------------------------------------------===//
738
739clang::sema::AnalysisBasedWarnings::Policy::Policy() {
740  enableCheckFallThrough = 1;
741  enableCheckUnreachable = 0;
742  enableThreadSafetyAnalysis = 0;
743}
744
745clang::sema::AnalysisBasedWarnings::AnalysisBasedWarnings(Sema &s)
746  : S(s),
747    NumFunctionsAnalyzed(0),
748    NumFunctionsWithBadCFGs(0),
749    NumCFGBlocks(0),
750    MaxCFGBlocksPerFunction(0),
751    NumUninitAnalysisFunctions(0),
752    NumUninitAnalysisVariables(0),
753    MaxUninitAnalysisVariablesPerFunction(0),
754    NumUninitAnalysisBlockVisits(0),
755    MaxUninitAnalysisBlockVisitsPerFunction(0) {
756  DiagnosticsEngine &D = S.getDiagnostics();
757  DefaultPolicy.enableCheckUnreachable = (unsigned)
758    (D.getDiagnosticLevel(diag::warn_unreachable, SourceLocation()) !=
759        DiagnosticsEngine::Ignored);
760  DefaultPolicy.enableThreadSafetyAnalysis = (unsigned)
761    (D.getDiagnosticLevel(diag::warn_double_lock, SourceLocation()) !=
762     DiagnosticsEngine::Ignored);
763
764}
765
766static void flushDiagnostics(Sema &S, sema::FunctionScopeInfo *fscope) {
767  for (SmallVectorImpl<sema::PossiblyUnreachableDiag>::iterator
768       i = fscope->PossiblyUnreachableDiags.begin(),
769       e = fscope->PossiblyUnreachableDiags.end();
770       i != e; ++i) {
771    const sema::PossiblyUnreachableDiag &D = *i;
772    S.Diag(D.Loc, D.PD);
773  }
774}
775
776void clang::sema::
777AnalysisBasedWarnings::IssueWarnings(sema::AnalysisBasedWarnings::Policy P,
778                                     sema::FunctionScopeInfo *fscope,
779                                     const Decl *D, const BlockExpr *blkExpr) {
780
781  // We avoid doing analysis-based warnings when there are errors for
782  // two reasons:
783  // (1) The CFGs often can't be constructed (if the body is invalid), so
784  //     don't bother trying.
785  // (2) The code already has problems; running the analysis just takes more
786  //     time.
787  DiagnosticsEngine &Diags = S.getDiagnostics();
788
789  // Do not do any analysis for declarations in system headers if we are
790  // going to just ignore them.
791  if (Diags.getSuppressSystemWarnings() &&
792      S.SourceMgr.isInSystemHeader(D->getLocation()))
793    return;
794
795  // For code in dependent contexts, we'll do this at instantiation time.
796  if (cast<DeclContext>(D)->isDependentContext())
797    return;
798
799  if (Diags.hasErrorOccurred() || Diags.hasFatalErrorOccurred()) {
800    // Flush out any possibly unreachable diagnostics.
801    flushDiagnostics(S, fscope);
802    return;
803  }
804
805  const Stmt *Body = D->getBody();
806  assert(Body);
807
808  AnalysisDeclContext AC(/* AnalysisDeclContextManager */ 0,  D, 0);
809
810  // Don't generate EH edges for CallExprs as we'd like to avoid the n^2
811  // explosion for destrutors that can result and the compile time hit.
812  AC.getCFGBuildOptions().PruneTriviallyFalseEdges = true;
813  AC.getCFGBuildOptions().AddEHEdges = false;
814  AC.getCFGBuildOptions().AddInitializers = true;
815  AC.getCFGBuildOptions().AddImplicitDtors = true;
816
817  // Force that certain expressions appear as CFGElements in the CFG.  This
818  // is used to speed up various analyses.
819  // FIXME: This isn't the right factoring.  This is here for initial
820  // prototyping, but we need a way for analyses to say what expressions they
821  // expect to always be CFGElements and then fill in the BuildOptions
822  // appropriately.  This is essentially a layering violation.
823  if (P.enableCheckUnreachable || P.enableThreadSafetyAnalysis) {
824    // Unreachable code analysis and thread safety require a linearized CFG.
825    AC.getCFGBuildOptions().setAllAlwaysAdd();
826  }
827  else {
828    AC.getCFGBuildOptions()
829      .setAlwaysAdd(Stmt::BinaryOperatorClass)
830      .setAlwaysAdd(Stmt::BlockExprClass)
831      .setAlwaysAdd(Stmt::CStyleCastExprClass)
832      .setAlwaysAdd(Stmt::DeclRefExprClass)
833      .setAlwaysAdd(Stmt::ImplicitCastExprClass)
834      .setAlwaysAdd(Stmt::UnaryOperatorClass);
835  }
836
837  // Construct the analysis context with the specified CFG build options.
838
839  // Emit delayed diagnostics.
840  if (!fscope->PossiblyUnreachableDiags.empty()) {
841    bool analyzed = false;
842
843    // Register the expressions with the CFGBuilder.
844    for (SmallVectorImpl<sema::PossiblyUnreachableDiag>::iterator
845         i = fscope->PossiblyUnreachableDiags.begin(),
846         e = fscope->PossiblyUnreachableDiags.end();
847         i != e; ++i) {
848      if (const Stmt *stmt = i->stmt)
849        AC.registerForcedBlockExpression(stmt);
850    }
851
852    if (AC.getCFG()) {
853      analyzed = true;
854      for (SmallVectorImpl<sema::PossiblyUnreachableDiag>::iterator
855            i = fscope->PossiblyUnreachableDiags.begin(),
856            e = fscope->PossiblyUnreachableDiags.end();
857            i != e; ++i)
858      {
859        const sema::PossiblyUnreachableDiag &D = *i;
860        bool processed = false;
861        if (const Stmt *stmt = i->stmt) {
862          const CFGBlock *block = AC.getBlockForRegisteredExpression(stmt);
863          CFGReverseBlockReachabilityAnalysis *cra =
864              AC.getCFGReachablityAnalysis();
865          // FIXME: We should be able to assert that block is non-null, but
866          // the CFG analysis can skip potentially-evaluated expressions in
867          // edge cases; see test/Sema/vla-2.c.
868          if (block && cra) {
869            // Can this block be reached from the entrance?
870            if (cra->isReachable(&AC.getCFG()->getEntry(), block))
871              S.Diag(D.Loc, D.PD);
872            processed = true;
873          }
874        }
875        if (!processed) {
876          // Emit the warning anyway if we cannot map to a basic block.
877          S.Diag(D.Loc, D.PD);
878        }
879      }
880    }
881
882    if (!analyzed)
883      flushDiagnostics(S, fscope);
884  }
885
886
887  // Warning: check missing 'return'
888  if (P.enableCheckFallThrough) {
889    const CheckFallThroughDiagnostics &CD =
890      (isa<BlockDecl>(D) ? CheckFallThroughDiagnostics::MakeForBlock()
891                         : CheckFallThroughDiagnostics::MakeForFunction(D));
892    CheckFallThroughForBody(S, D, Body, blkExpr, CD, AC);
893  }
894
895  // Warning: check for unreachable code
896  if (P.enableCheckUnreachable) {
897    // Only check for unreachable code on non-template instantiations.
898    // Different template instantiations can effectively change the control-flow
899    // and it is very difficult to prove that a snippet of code in a template
900    // is unreachable for all instantiations.
901    bool isTemplateInstantiation = false;
902    if (const FunctionDecl *Function = dyn_cast<FunctionDecl>(D))
903      isTemplateInstantiation = Function->isTemplateInstantiation();
904    if (!isTemplateInstantiation)
905      CheckUnreachable(S, AC);
906  }
907
908  // Check for thread safety violations
909  if (P.enableThreadSafetyAnalysis) {
910    SourceLocation FL = AC.getDecl()->getLocation();
911    SourceLocation FEL = AC.getDecl()->getLocEnd();
912    thread_safety::ThreadSafetyReporter Reporter(S, FL, FEL);
913    thread_safety::runThreadSafetyAnalysis(AC, Reporter);
914    Reporter.emitDiagnostics();
915  }
916
917  if (Diags.getDiagnosticLevel(diag::warn_uninit_var, D->getLocStart())
918      != DiagnosticsEngine::Ignored ||
919      Diags.getDiagnosticLevel(diag::warn_maybe_uninit_var, D->getLocStart())
920      != DiagnosticsEngine::Ignored) {
921    if (CFG *cfg = AC.getCFG()) {
922      UninitValsDiagReporter reporter(S);
923      UninitVariablesAnalysisStats stats;
924      std::memset(&stats, 0, sizeof(UninitVariablesAnalysisStats));
925      runUninitializedVariablesAnalysis(*cast<DeclContext>(D), *cfg, AC,
926                                        reporter, stats);
927
928      if (S.CollectStats && stats.NumVariablesAnalyzed > 0) {
929        ++NumUninitAnalysisFunctions;
930        NumUninitAnalysisVariables += stats.NumVariablesAnalyzed;
931        NumUninitAnalysisBlockVisits += stats.NumBlockVisits;
932        MaxUninitAnalysisVariablesPerFunction =
933            std::max(MaxUninitAnalysisVariablesPerFunction,
934                     stats.NumVariablesAnalyzed);
935        MaxUninitAnalysisBlockVisitsPerFunction =
936            std::max(MaxUninitAnalysisBlockVisitsPerFunction,
937                     stats.NumBlockVisits);
938      }
939    }
940  }
941
942  // Collect statistics about the CFG if it was built.
943  if (S.CollectStats && AC.isCFGBuilt()) {
944    ++NumFunctionsAnalyzed;
945    if (CFG *cfg = AC.getCFG()) {
946      // If we successfully built a CFG for this context, record some more
947      // detail information about it.
948      NumCFGBlocks += cfg->getNumBlockIDs();
949      MaxCFGBlocksPerFunction = std::max(MaxCFGBlocksPerFunction,
950                                         cfg->getNumBlockIDs());
951    } else {
952      ++NumFunctionsWithBadCFGs;
953    }
954  }
955}
956
957void clang::sema::AnalysisBasedWarnings::PrintStats() const {
958  llvm::errs() << "\n*** Analysis Based Warnings Stats:\n";
959
960  unsigned NumCFGsBuilt = NumFunctionsAnalyzed - NumFunctionsWithBadCFGs;
961  unsigned AvgCFGBlocksPerFunction =
962      !NumCFGsBuilt ? 0 : NumCFGBlocks/NumCFGsBuilt;
963  llvm::errs() << NumFunctionsAnalyzed << " functions analyzed ("
964               << NumFunctionsWithBadCFGs << " w/o CFGs).\n"
965               << "  " << NumCFGBlocks << " CFG blocks built.\n"
966               << "  " << AvgCFGBlocksPerFunction
967               << " average CFG blocks per function.\n"
968               << "  " << MaxCFGBlocksPerFunction
969               << " max CFG blocks per function.\n";
970
971  unsigned AvgUninitVariablesPerFunction = !NumUninitAnalysisFunctions ? 0
972      : NumUninitAnalysisVariables/NumUninitAnalysisFunctions;
973  unsigned AvgUninitBlockVisitsPerFunction = !NumUninitAnalysisFunctions ? 0
974      : NumUninitAnalysisBlockVisits/NumUninitAnalysisFunctions;
975  llvm::errs() << NumUninitAnalysisFunctions
976               << " functions analyzed for uninitialiazed variables\n"
977               << "  " << NumUninitAnalysisVariables << " variables analyzed.\n"
978               << "  " << AvgUninitVariablesPerFunction
979               << " average variables per function.\n"
980               << "  " << MaxUninitAnalysisVariablesPerFunction
981               << " max variables per function.\n"
982               << "  " << NumUninitAnalysisBlockVisits << " block visits.\n"
983               << "  " << AvgUninitBlockVisitsPerFunction
984               << " average block visits per function.\n"
985               << "  " << MaxUninitAnalysisBlockVisitsPerFunction
986               << " max block visits per function.\n";
987}
988