AnalysisBasedWarnings.cpp revision b1b5daf30d2597e066936772bd206500232d7d65 
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, AnalysisContext &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(AnalysisContext &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      switch (Function->getTemplateSpecializationKind()) {
246      case TSK_Undeclared:
247      case TSK_ExplicitSpecialization:
248        break;
249
250      case TSK_ImplicitInstantiation:
251      case TSK_ExplicitInstantiationDeclaration:
252      case TSK_ExplicitInstantiationDefinition:
253        isTemplateInstantiation = true;
254        break;
255      }
256    }
257
258    if (!isVirtualMethod && !isTemplateInstantiation)
259      D.diag_NeverFallThroughOrReturn =
260        diag::warn_suggest_noreturn_function;
261    else
262      D.diag_NeverFallThroughOrReturn = 0;
263
264    D.funMode = true;
265    return D;
266  }
267
268  static CheckFallThroughDiagnostics MakeForBlock() {
269    CheckFallThroughDiagnostics D;
270    D.diag_MaybeFallThrough_HasNoReturn =
271      diag::err_noreturn_block_has_return_expr;
272    D.diag_MaybeFallThrough_ReturnsNonVoid =
273      diag::err_maybe_falloff_nonvoid_block;
274    D.diag_AlwaysFallThrough_HasNoReturn =
275      diag::err_noreturn_block_has_return_expr;
276    D.diag_AlwaysFallThrough_ReturnsNonVoid =
277      diag::err_falloff_nonvoid_block;
278    D.diag_NeverFallThroughOrReturn =
279      diag::warn_suggest_noreturn_block;
280    D.funMode = false;
281    return D;
282  }
283
284  bool checkDiagnostics(DiagnosticsEngine &D, bool ReturnsVoid,
285                        bool HasNoReturn) const {
286    if (funMode) {
287      return (ReturnsVoid ||
288              D.getDiagnosticLevel(diag::warn_maybe_falloff_nonvoid_function,
289                                   FuncLoc) == DiagnosticsEngine::Ignored)
290        && (!HasNoReturn ||
291            D.getDiagnosticLevel(diag::warn_noreturn_function_has_return_expr,
292                                 FuncLoc) == DiagnosticsEngine::Ignored)
293        && (!ReturnsVoid ||
294            D.getDiagnosticLevel(diag::warn_suggest_noreturn_block, FuncLoc)
295              == DiagnosticsEngine::Ignored);
296    }
297
298    // For blocks.
299    return  ReturnsVoid && !HasNoReturn
300            && (!ReturnsVoid ||
301                D.getDiagnosticLevel(diag::warn_suggest_noreturn_block, FuncLoc)
302                  == DiagnosticsEngine::Ignored);
303  }
304};
305
306}
307
308/// CheckFallThroughForFunctionDef - Check that we don't fall off the end of a
309/// function that should return a value.  Check that we don't fall off the end
310/// of a noreturn function.  We assume that functions and blocks not marked
311/// noreturn will return.
312static void CheckFallThroughForBody(Sema &S, const Decl *D, const Stmt *Body,
313                                    const BlockExpr *blkExpr,
314                                    const CheckFallThroughDiagnostics& CD,
315                                    AnalysisContext &AC) {
316
317  bool ReturnsVoid = false;
318  bool HasNoReturn = false;
319
320  if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
321    ReturnsVoid = FD->getResultType()->isVoidType();
322    HasNoReturn = FD->hasAttr<NoReturnAttr>() ||
323       FD->getType()->getAs<FunctionType>()->getNoReturnAttr();
324  }
325  else if (const ObjCMethodDecl *MD = dyn_cast<ObjCMethodDecl>(D)) {
326    ReturnsVoid = MD->getResultType()->isVoidType();
327    HasNoReturn = MD->hasAttr<NoReturnAttr>();
328  }
329  else if (isa<BlockDecl>(D)) {
330    QualType BlockTy = blkExpr->getType();
331    if (const FunctionType *FT =
332          BlockTy->getPointeeType()->getAs<FunctionType>()) {
333      if (FT->getResultType()->isVoidType())
334        ReturnsVoid = true;
335      if (FT->getNoReturnAttr())
336        HasNoReturn = true;
337    }
338  }
339
340  DiagnosticsEngine &Diags = S.getDiagnostics();
341
342  // Short circuit for compilation speed.
343  if (CD.checkDiagnostics(Diags, ReturnsVoid, HasNoReturn))
344      return;
345
346  // FIXME: Function try block
347  if (const CompoundStmt *Compound = dyn_cast<CompoundStmt>(Body)) {
348    switch (CheckFallThrough(AC)) {
349      case UnknownFallThrough:
350        break;
351
352      case MaybeFallThrough:
353        if (HasNoReturn)
354          S.Diag(Compound->getRBracLoc(),
355                 CD.diag_MaybeFallThrough_HasNoReturn);
356        else if (!ReturnsVoid)
357          S.Diag(Compound->getRBracLoc(),
358                 CD.diag_MaybeFallThrough_ReturnsNonVoid);
359        break;
360      case AlwaysFallThrough:
361        if (HasNoReturn)
362          S.Diag(Compound->getRBracLoc(),
363                 CD.diag_AlwaysFallThrough_HasNoReturn);
364        else if (!ReturnsVoid)
365          S.Diag(Compound->getRBracLoc(),
366                 CD.diag_AlwaysFallThrough_ReturnsNonVoid);
367        break;
368      case NeverFallThroughOrReturn:
369        if (ReturnsVoid && !HasNoReturn && CD.diag_NeverFallThroughOrReturn) {
370          if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
371            S.Diag(Compound->getLBracLoc(), CD.diag_NeverFallThroughOrReturn)
372              << 0 << FD;
373          } else if (const ObjCMethodDecl *MD = dyn_cast<ObjCMethodDecl>(D)) {
374            S.Diag(Compound->getLBracLoc(), CD.diag_NeverFallThroughOrReturn)
375              << 1 << MD;
376          } else {
377            S.Diag(Compound->getLBracLoc(), CD.diag_NeverFallThroughOrReturn);
378          }
379        }
380        break;
381      case NeverFallThrough:
382        break;
383    }
384  }
385}
386
387//===----------------------------------------------------------------------===//
388// -Wuninitialized
389//===----------------------------------------------------------------------===//
390
391namespace {
392/// ContainsReference - A visitor class to search for references to
393/// a particular declaration (the needle) within any evaluated component of an
394/// expression (recursively).
395class ContainsReference : public EvaluatedExprVisitor<ContainsReference> {
396  bool FoundReference;
397  const DeclRefExpr *Needle;
398
399public:
400  ContainsReference(ASTContext &Context, const DeclRefExpr *Needle)
401    : EvaluatedExprVisitor<ContainsReference>(Context),
402      FoundReference(false), Needle(Needle) {}
403
404  void VisitExpr(Expr *E) {
405    // Stop evaluating if we already have a reference.
406    if (FoundReference)
407      return;
408
409    EvaluatedExprVisitor<ContainsReference>::VisitExpr(E);
410  }
411
412  void VisitDeclRefExpr(DeclRefExpr *E) {
413    if (E == Needle)
414      FoundReference = true;
415    else
416      EvaluatedExprVisitor<ContainsReference>::VisitDeclRefExpr(E);
417  }
418
419  bool doesContainReference() const { return FoundReference; }
420};
421}
422
423static bool SuggestInitializationFixit(Sema &S, const VarDecl *VD) {
424  // Don't issue a fixit if there is already an initializer.
425  if (VD->getInit())
426    return false;
427
428  // Suggest possible initialization (if any).
429  const char *initialization = 0;
430  QualType VariableTy = VD->getType().getCanonicalType();
431
432  if (VariableTy->isObjCObjectPointerType() ||
433      VariableTy->isBlockPointerType()) {
434    // Check if 'nil' is defined.
435    if (S.PP.getMacroInfo(&S.getASTContext().Idents.get("nil")))
436      initialization = " = nil";
437    else
438      initialization = " = 0";
439  }
440  else if (VariableTy->isRealFloatingType())
441    initialization = " = 0.0";
442  else if (VariableTy->isBooleanType() && S.Context.getLangOptions().CPlusPlus)
443    initialization = " = false";
444  else if (VariableTy->isEnumeralType())
445    return false;
446  else if (VariableTy->isPointerType() || VariableTy->isMemberPointerType()) {
447    if (S.Context.getLangOptions().CPlusPlus0x)
448      initialization = " = nullptr";
449    // Check if 'NULL' is defined.
450    else if (S.PP.getMacroInfo(&S.getASTContext().Idents.get("NULL")))
451      initialization = " = NULL";
452    else
453      initialization = " = 0";
454  }
455  else if (VariableTy->isScalarType())
456    initialization = " = 0";
457
458  if (initialization) {
459    SourceLocation loc = S.PP.getLocForEndOfToken(VD->getLocEnd());
460    S.Diag(loc, diag::note_var_fixit_add_initialization) << VD->getDeclName()
461      << FixItHint::CreateInsertion(loc, initialization);
462    return true;
463  }
464  return false;
465}
466
467/// DiagnoseUninitializedUse -- Helper function for diagnosing uses of an
468/// uninitialized variable. This manages the different forms of diagnostic
469/// emitted for particular types of uses. Returns true if the use was diagnosed
470/// as a warning. If a pariticular use is one we omit warnings for, returns
471/// false.
472static bool DiagnoseUninitializedUse(Sema &S, const VarDecl *VD,
473                                     const Expr *E, bool isAlwaysUninit,
474                                     bool alwaysReportSelfInit = false) {
475  bool isSelfInit = false;
476
477  if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E)) {
478    if (isAlwaysUninit) {
479      // Inspect the initializer of the variable declaration which is
480      // being referenced prior to its initialization. We emit
481      // specialized diagnostics for self-initialization, and we
482      // specifically avoid warning about self references which take the
483      // form of:
484      //
485      //   int x = x;
486      //
487      // This is used to indicate to GCC that 'x' is intentionally left
488      // uninitialized. Proven code paths which access 'x' in
489      // an uninitialized state after this will still warn.
490      //
491      // TODO: Should we suppress maybe-uninitialized warnings for
492      // variables initialized in this way?
493      if (const Expr *Initializer = VD->getInit()) {
494        if (!alwaysReportSelfInit && DRE == Initializer->IgnoreParenImpCasts())
495          return false;
496
497        ContainsReference CR(S.Context, DRE);
498        CR.Visit(const_cast<Expr*>(Initializer));
499        isSelfInit = CR.doesContainReference();
500      }
501      if (isSelfInit) {
502        S.Diag(DRE->getLocStart(),
503               diag::warn_uninit_self_reference_in_init)
504        << VD->getDeclName() << VD->getLocation() << DRE->getSourceRange();
505      } else {
506        S.Diag(DRE->getLocStart(), diag::warn_uninit_var)
507          << VD->getDeclName() << DRE->getSourceRange();
508      }
509    } else {
510      S.Diag(DRE->getLocStart(), diag::warn_maybe_uninit_var)
511        << VD->getDeclName() << DRE->getSourceRange();
512    }
513  } else {
514    const BlockExpr *BE = cast<BlockExpr>(E);
515    S.Diag(BE->getLocStart(),
516           isAlwaysUninit ? diag::warn_uninit_var_captured_by_block
517                          : diag::warn_maybe_uninit_var_captured_by_block)
518      << VD->getDeclName();
519  }
520
521  // Report where the variable was declared when the use wasn't within
522  // the initializer of that declaration & we didn't already suggest
523  // an initialization fixit.
524  if (!isSelfInit && !SuggestInitializationFixit(S, VD))
525    S.Diag(VD->getLocStart(), diag::note_uninit_var_def)
526      << VD->getDeclName();
527
528  return true;
529}
530
531typedef std::pair<const Expr*, bool> UninitUse;
532
533namespace {
534struct SLocSort {
535  bool operator()(const UninitUse &a, const UninitUse &b) {
536    SourceLocation aLoc = a.first->getLocStart();
537    SourceLocation bLoc = b.first->getLocStart();
538    return aLoc.getRawEncoding() < bLoc.getRawEncoding();
539  }
540};
541
542class UninitValsDiagReporter : public UninitVariablesHandler {
543  Sema &S;
544  typedef SmallVector<UninitUse, 2> UsesVec;
545  typedef llvm::DenseMap<const VarDecl *, std::pair<UsesVec*, bool> > UsesMap;
546  UsesMap *uses;
547
548public:
549  UninitValsDiagReporter(Sema &S) : S(S), uses(0) {}
550  ~UninitValsDiagReporter() {
551    flushDiagnostics();
552  }
553
554  std::pair<UsesVec*, bool> &getUses(const VarDecl *vd) {
555    if (!uses)
556      uses = new UsesMap();
557
558    UsesMap::mapped_type &V = (*uses)[vd];
559    UsesVec *&vec = V.first;
560    if (!vec)
561      vec = new UsesVec();
562
563    return V;
564  }
565
566  void handleUseOfUninitVariable(const Expr *ex, const VarDecl *vd,
567                                 bool isAlwaysUninit) {
568    getUses(vd).first->push_back(std::make_pair(ex, isAlwaysUninit));
569  }
570
571  void handleSelfInit(const VarDecl *vd) {
572    getUses(vd).second = true;
573  }
574
575  void flushDiagnostics() {
576    if (!uses)
577      return;
578
579    for (UsesMap::iterator i = uses->begin(), e = uses->end(); i != e; ++i) {
580      const VarDecl *vd = i->first;
581      const UsesMap::mapped_type &V = i->second;
582
583      UsesVec *vec = V.first;
584      bool hasSelfInit = V.second;
585
586      // Specially handle the case where we have uses of an uninitialized
587      // variable, but the root cause is an idiomatic self-init.  We want
588      // to report the diagnostic at the self-init since that is the root cause.
589      if (!vec->empty() && hasSelfInit && hasAlwaysUninitializedUse(vec))
590        DiagnoseUninitializedUse(S, vd, vd->getInit()->IgnoreParenCasts(),
591                                 /* isAlwaysUninit */ true,
592                                 /* alwaysReportSelfInit */ true);
593      else {
594        // Sort the uses by their SourceLocations.  While not strictly
595        // guaranteed to produce them in line/column order, this will provide
596        // a stable ordering.
597        std::sort(vec->begin(), vec->end(), SLocSort());
598
599        for (UsesVec::iterator vi = vec->begin(), ve = vec->end(); vi != ve;
600             ++vi) {
601          if (DiagnoseUninitializedUse(S, vd, vi->first,
602                                        /*isAlwaysUninit=*/vi->second))
603            // Skip further diagnostics for this variable. We try to warn only
604            // on the first point at which a variable is used uninitialized.
605            break;
606        }
607      }
608
609      // Release the uses vector.
610      delete vec;
611    }
612    delete uses;
613  }
614
615private:
616  static bool hasAlwaysUninitializedUse(const UsesVec* vec) {
617  for (UsesVec::const_iterator i = vec->begin(), e = vec->end(); i != e; ++i) {
618    if (i->second) {
619      return true;
620    }
621  }
622  return false;
623}
624};
625}
626
627
628//===----------------------------------------------------------------------===//
629// -Wthread-safety
630//===----------------------------------------------------------------------===//
631namespace clang {
632namespace thread_safety {
633typedef std::pair<SourceLocation, PartialDiagnostic> DelayedDiag;
634typedef llvm::SmallVector<DelayedDiag, 4> DiagList;
635
636struct SortDiagBySourceLocation {
637  Sema &S;
638  SortDiagBySourceLocation(Sema &S) : S(S) {}
639
640  bool operator()(const DelayedDiag &left, const DelayedDiag &right) {
641    // Although this call will be slow, this is only called when outputting
642    // multiple warnings.
643    return S.getSourceManager().isBeforeInTranslationUnit(left.first,
644                                                          right.first);
645  }
646};
647
648class ThreadSafetyReporter : public clang::thread_safety::ThreadSafetyHandler {
649  Sema &S;
650  DiagList Warnings;
651  SourceLocation FunLocation;
652
653  // Helper functions
654  void warnLockMismatch(unsigned DiagID, Name LockName, SourceLocation Loc) {
655    // Gracefully handle rare cases when the analysis can't get a more
656    // precise source location.
657    if (!Loc.isValid())
658      Loc = FunLocation;
659    PartialDiagnostic Warning = S.PDiag(DiagID) << LockName;
660    Warnings.push_back(DelayedDiag(Loc, Warning));
661  }
662
663 public:
664  ThreadSafetyReporter(Sema &S, SourceLocation FL)
665    : S(S), FunLocation(FL) {}
666
667  /// \brief Emit all buffered diagnostics in order of sourcelocation.
668  /// We need to output diagnostics produced while iterating through
669  /// the lockset in deterministic order, so this function orders diagnostics
670  /// and outputs them.
671  void emitDiagnostics() {
672    SortDiagBySourceLocation SortDiagBySL(S);
673    sort(Warnings.begin(), Warnings.end(), SortDiagBySL);
674    for (DiagList::iterator I = Warnings.begin(), E = Warnings.end();
675         I != E; ++I)
676      S.Diag(I->first, I->second);
677  }
678
679  void handleInvalidLockExp(SourceLocation Loc) {
680    PartialDiagnostic Warning = S.PDiag(diag::warn_cannot_resolve_lock) << Loc;
681    Warnings.push_back(DelayedDiag(Loc, Warning));
682  }
683  void handleUnmatchedUnlock(Name LockName, SourceLocation Loc) {
684    warnLockMismatch(diag::warn_unlock_but_no_lock, LockName, Loc);
685  }
686
687  void handleDoubleLock(Name LockName, SourceLocation Loc) {
688    warnLockMismatch(diag::warn_double_lock, LockName, Loc);
689  }
690
691  void handleMutexHeldEndOfScope(Name LockName, SourceLocation Loc,
692                                 LockErrorKind LEK){
693    unsigned DiagID = 0;
694    switch (LEK) {
695      case LEK_LockedSomePredecessors:
696        DiagID = diag::warn_lock_at_end_of_scope;
697        break;
698      case LEK_LockedSomeLoopIterations:
699        DiagID = diag::warn_expecting_lock_held_on_loop;
700        break;
701      case LEK_LockedAtEndOfFunction:
702        DiagID = diag::warn_no_unlock;
703        break;
704    }
705    warnLockMismatch(DiagID, LockName, Loc);
706  }
707
708
709  void handleExclusiveAndShared(Name LockName, SourceLocation Loc1,
710                                SourceLocation Loc2) {
711    PartialDiagnostic Warning =
712      S.PDiag(diag::warn_lock_exclusive_and_shared) << LockName;
713    PartialDiagnostic Note =
714      S.PDiag(diag::note_lock_exclusive_and_shared) << LockName;
715    Warnings.push_back(DelayedDiag(Loc1, Warning));
716    Warnings.push_back(DelayedDiag(Loc2, Note));
717  }
718
719  void handleNoMutexHeld(const NamedDecl *D, ProtectedOperationKind POK,
720                         AccessKind AK, SourceLocation Loc) {
721    assert((POK == POK_VarAccess || POK == POK_VarDereference)
722             && "Only works for variables");
723    unsigned DiagID = POK == POK_VarAccess?
724                        diag::warn_variable_requires_any_lock:
725                        diag::warn_var_deref_requires_any_lock;
726    PartialDiagnostic Warning = S.PDiag(DiagID)
727      << D->getName() << getLockKindFromAccessKind(AK);
728    Warnings.push_back(DelayedDiag(Loc, Warning));
729  }
730
731  void handleMutexNotHeld(const NamedDecl *D, ProtectedOperationKind POK,
732                          Name LockName, LockKind LK, SourceLocation Loc) {
733    unsigned DiagID = 0;
734    switch (POK) {
735      case POK_VarAccess:
736        DiagID = diag::warn_variable_requires_lock;
737        break;
738      case POK_VarDereference:
739        DiagID = diag::warn_var_deref_requires_lock;
740        break;
741      case POK_FunctionCall:
742        DiagID = diag::warn_fun_requires_lock;
743        break;
744    }
745    PartialDiagnostic Warning = S.PDiag(DiagID)
746      << D->getName() << LockName << LK;
747    Warnings.push_back(DelayedDiag(Loc, Warning));
748  }
749
750  void handleFunExcludesLock(Name FunName, Name LockName, SourceLocation Loc) {
751    PartialDiagnostic Warning =
752      S.PDiag(diag::warn_fun_excludes_mutex) << FunName << LockName;
753    Warnings.push_back(DelayedDiag(Loc, Warning));
754  }
755};
756}
757}
758
759//===----------------------------------------------------------------------===//
760// AnalysisBasedWarnings - Worker object used by Sema to execute analysis-based
761//  warnings on a function, method, or block.
762//===----------------------------------------------------------------------===//
763
764clang::sema::AnalysisBasedWarnings::Policy::Policy() {
765  enableCheckFallThrough = 1;
766  enableCheckUnreachable = 0;
767  enableThreadSafetyAnalysis = 0;
768}
769
770clang::sema::AnalysisBasedWarnings::AnalysisBasedWarnings(Sema &s)
771  : S(s),
772    NumFunctionsAnalyzed(0),
773    NumFunctionsWithBadCFGs(0),
774    NumCFGBlocks(0),
775    MaxCFGBlocksPerFunction(0),
776    NumUninitAnalysisFunctions(0),
777    NumUninitAnalysisVariables(0),
778    MaxUninitAnalysisVariablesPerFunction(0),
779    NumUninitAnalysisBlockVisits(0),
780    MaxUninitAnalysisBlockVisitsPerFunction(0) {
781  DiagnosticsEngine &D = S.getDiagnostics();
782  DefaultPolicy.enableCheckUnreachable = (unsigned)
783    (D.getDiagnosticLevel(diag::warn_unreachable, SourceLocation()) !=
784        DiagnosticsEngine::Ignored);
785  DefaultPolicy.enableThreadSafetyAnalysis = (unsigned)
786    (D.getDiagnosticLevel(diag::warn_double_lock, SourceLocation()) !=
787     DiagnosticsEngine::Ignored);
788
789}
790
791static void flushDiagnostics(Sema &S, sema::FunctionScopeInfo *fscope) {
792  for (SmallVectorImpl<sema::PossiblyUnreachableDiag>::iterator
793       i = fscope->PossiblyUnreachableDiags.begin(),
794       e = fscope->PossiblyUnreachableDiags.end();
795       i != e; ++i) {
796    const sema::PossiblyUnreachableDiag &D = *i;
797    S.Diag(D.Loc, D.PD);
798  }
799}
800
801void clang::sema::
802AnalysisBasedWarnings::IssueWarnings(sema::AnalysisBasedWarnings::Policy P,
803                                     sema::FunctionScopeInfo *fscope,
804                                     const Decl *D, const BlockExpr *blkExpr) {
805
806  // We avoid doing analysis-based warnings when there are errors for
807  // two reasons:
808  // (1) The CFGs often can't be constructed (if the body is invalid), so
809  //     don't bother trying.
810  // (2) The code already has problems; running the analysis just takes more
811  //     time.
812  DiagnosticsEngine &Diags = S.getDiagnostics();
813
814  // Do not do any analysis for declarations in system headers if we are
815  // going to just ignore them.
816  if (Diags.getSuppressSystemWarnings() &&
817      S.SourceMgr.isInSystemHeader(D->getLocation()))
818    return;
819
820  // For code in dependent contexts, we'll do this at instantiation time.
821  if (cast<DeclContext>(D)->isDependentContext())
822    return;
823
824  if (Diags.hasErrorOccurred() || Diags.hasFatalErrorOccurred()) {
825    // Flush out any possibly unreachable diagnostics.
826    flushDiagnostics(S, fscope);
827    return;
828  }
829
830  const Stmt *Body = D->getBody();
831  assert(Body);
832
833  AnalysisContext AC(/* AnalysisContextManager */ 0,  D, 0);
834
835  // Don't generate EH edges for CallExprs as we'd like to avoid the n^2
836  // explosion for destrutors that can result and the compile time hit.
837  AC.getCFGBuildOptions().PruneTriviallyFalseEdges = true;
838  AC.getCFGBuildOptions().AddEHEdges = false;
839  AC.getCFGBuildOptions().AddInitializers = true;
840  AC.getCFGBuildOptions().AddImplicitDtors = true;
841
842  // Force that certain expressions appear as CFGElements in the CFG.  This
843  // is used to speed up various analyses.
844  // FIXME: This isn't the right factoring.  This is here for initial
845  // prototyping, but we need a way for analyses to say what expressions they
846  // expect to always be CFGElements and then fill in the BuildOptions
847  // appropriately.  This is essentially a layering violation.
848  if (P.enableCheckUnreachable) {
849    // Unreachable code analysis requires a linearized CFG.
850    AC.getCFGBuildOptions().setAllAlwaysAdd();
851  }
852  else {
853    AC.getCFGBuildOptions()
854      .setAlwaysAdd(Stmt::BinaryOperatorClass)
855      .setAlwaysAdd(Stmt::BlockExprClass)
856      .setAlwaysAdd(Stmt::CStyleCastExprClass)
857      .setAlwaysAdd(Stmt::DeclRefExprClass)
858      .setAlwaysAdd(Stmt::ImplicitCastExprClass)
859      .setAlwaysAdd(Stmt::UnaryOperatorClass);
860  }
861
862  // Construct the analysis context with the specified CFG build options.
863
864  // Emit delayed diagnostics.
865  if (!fscope->PossiblyUnreachableDiags.empty()) {
866    bool analyzed = false;
867
868    // Register the expressions with the CFGBuilder.
869    for (SmallVectorImpl<sema::PossiblyUnreachableDiag>::iterator
870         i = fscope->PossiblyUnreachableDiags.begin(),
871         e = fscope->PossiblyUnreachableDiags.end();
872         i != e; ++i) {
873      if (const Stmt *stmt = i->stmt)
874        AC.registerForcedBlockExpression(stmt);
875    }
876
877    if (AC.getCFG()) {
878      analyzed = true;
879      for (SmallVectorImpl<sema::PossiblyUnreachableDiag>::iterator
880            i = fscope->PossiblyUnreachableDiags.begin(),
881            e = fscope->PossiblyUnreachableDiags.end();
882            i != e; ++i)
883      {
884        const sema::PossiblyUnreachableDiag &D = *i;
885        bool processed = false;
886        if (const Stmt *stmt = i->stmt) {
887          const CFGBlock *block = AC.getBlockForRegisteredExpression(stmt);
888          assert(block);
889          if (CFGReverseBlockReachabilityAnalysis *cra = AC.getCFGReachablityAnalysis()) {
890            // Can this block be reached from the entrance?
891            if (cra->isReachable(&AC.getCFG()->getEntry(), block))
892              S.Diag(D.Loc, D.PD);
893            processed = true;
894          }
895        }
896        if (!processed) {
897          // Emit the warning anyway if we cannot map to a basic block.
898          S.Diag(D.Loc, D.PD);
899        }
900      }
901    }
902
903    if (!analyzed)
904      flushDiagnostics(S, fscope);
905  }
906
907
908  // Warning: check missing 'return'
909  if (P.enableCheckFallThrough) {
910    const CheckFallThroughDiagnostics &CD =
911      (isa<BlockDecl>(D) ? CheckFallThroughDiagnostics::MakeForBlock()
912                         : CheckFallThroughDiagnostics::MakeForFunction(D));
913    CheckFallThroughForBody(S, D, Body, blkExpr, CD, AC);
914  }
915
916  // Warning: check for unreachable code
917  if (P.enableCheckUnreachable)
918    CheckUnreachable(S, AC);
919
920  // Check for thread safety violations
921  if (P.enableThreadSafetyAnalysis) {
922    SourceLocation FL = AC.getDecl()->getLocation();
923    thread_safety::ThreadSafetyReporter Reporter(S, FL);
924    thread_safety::runThreadSafetyAnalysis(AC, Reporter);
925    Reporter.emitDiagnostics();
926  }
927
928  if (Diags.getDiagnosticLevel(diag::warn_uninit_var, D->getLocStart())
929      != DiagnosticsEngine::Ignored ||
930      Diags.getDiagnosticLevel(diag::warn_maybe_uninit_var, D->getLocStart())
931      != DiagnosticsEngine::Ignored) {
932    if (CFG *cfg = AC.getCFG()) {
933      UninitValsDiagReporter reporter(S);
934      UninitVariablesAnalysisStats stats;
935      std::memset(&stats, 0, sizeof(UninitVariablesAnalysisStats));
936      runUninitializedVariablesAnalysis(*cast<DeclContext>(D), *cfg, AC,
937                                        reporter, stats);
938
939      if (S.CollectStats && stats.NumVariablesAnalyzed > 0) {
940        ++NumUninitAnalysisFunctions;
941        NumUninitAnalysisVariables += stats.NumVariablesAnalyzed;
942        NumUninitAnalysisBlockVisits += stats.NumBlockVisits;
943        MaxUninitAnalysisVariablesPerFunction =
944            std::max(MaxUninitAnalysisVariablesPerFunction,
945                     stats.NumVariablesAnalyzed);
946        MaxUninitAnalysisBlockVisitsPerFunction =
947            std::max(MaxUninitAnalysisBlockVisitsPerFunction,
948                     stats.NumBlockVisits);
949      }
950    }
951  }
952
953  // Collect statistics about the CFG if it was built.
954  if (S.CollectStats && AC.isCFGBuilt()) {
955    ++NumFunctionsAnalyzed;
956    if (CFG *cfg = AC.getCFG()) {
957      // If we successfully built a CFG for this context, record some more
958      // detail information about it.
959      NumCFGBlocks += cfg->getNumBlockIDs();
960      MaxCFGBlocksPerFunction = std::max(MaxCFGBlocksPerFunction,
961                                         cfg->getNumBlockIDs());
962    } else {
963      ++NumFunctionsWithBadCFGs;
964    }
965  }
966}
967
968void clang::sema::AnalysisBasedWarnings::PrintStats() const {
969  llvm::errs() << "\n*** Analysis Based Warnings Stats:\n";
970
971  unsigned NumCFGsBuilt = NumFunctionsAnalyzed - NumFunctionsWithBadCFGs;
972  unsigned AvgCFGBlocksPerFunction =
973      !NumCFGsBuilt ? 0 : NumCFGBlocks/NumCFGsBuilt;
974  llvm::errs() << NumFunctionsAnalyzed << " functions analyzed ("
975               << NumFunctionsWithBadCFGs << " w/o CFGs).\n"
976               << "  " << NumCFGBlocks << " CFG blocks built.\n"
977               << "  " << AvgCFGBlocksPerFunction
978               << " average CFG blocks per function.\n"
979               << "  " << MaxCFGBlocksPerFunction
980               << " max CFG blocks per function.\n";
981
982  unsigned AvgUninitVariablesPerFunction = !NumUninitAnalysisFunctions ? 0
983      : NumUninitAnalysisVariables/NumUninitAnalysisFunctions;
984  unsigned AvgUninitBlockVisitsPerFunction = !NumUninitAnalysisFunctions ? 0
985      : NumUninitAnalysisBlockVisits/NumUninitAnalysisFunctions;
986  llvm::errs() << NumUninitAnalysisFunctions
987               << " functions analyzed for uninitialiazed variables\n"
988               << "  " << NumUninitAnalysisVariables << " variables analyzed.\n"
989               << "  " << AvgUninitVariablesPerFunction
990               << " average variables per function.\n"
991               << "  " << MaxUninitAnalysisVariablesPerFunction
992               << " max variables per function.\n"
993               << "  " << NumUninitAnalysisBlockVisits << " block visits.\n"
994               << "  " << AvgUninitBlockVisitsPerFunction
995               << " average block visits per function.\n"
996               << "  " << MaxUninitAnalysisBlockVisitsPerFunction
997               << " max block visits per function.\n";
998}
999