AnalysisBasedWarnings.cpp revision 99ba9e3bd70671f3441fb974895f226a83ce0e66 
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  const char *initialization = 0;
419  QualType VariableTy = VD->getType().getCanonicalType();
420
421  if (VariableTy->isObjCObjectPointerType() ||
422      VariableTy->isBlockPointerType()) {
423    // Check if 'nil' is defined.
424    if (S.PP.getMacroInfo(&S.getASTContext().Idents.get("nil")))
425      initialization = " = nil";
426    else
427      initialization = " = 0";
428  }
429  else if (VariableTy->isRealFloatingType())
430    initialization = " = 0.0";
431  else if (VariableTy->isBooleanType() && S.Context.getLangOptions().CPlusPlus)
432    initialization = " = false";
433  else if (VariableTy->isEnumeralType())
434    return false;
435  else if (VariableTy->isPointerType() || VariableTy->isMemberPointerType()) {
436    if (S.Context.getLangOptions().CPlusPlus0x)
437      initialization = " = nullptr";
438    // Check if 'NULL' is defined.
439    else if (S.PP.getMacroInfo(&S.getASTContext().Idents.get("NULL")))
440      initialization = " = NULL";
441    else
442      initialization = " = 0";
443  }
444  else if (VariableTy->isScalarType())
445    initialization = " = 0";
446
447  if (initialization) {
448    SourceLocation loc = S.PP.getLocForEndOfToken(VD->getLocEnd());
449    S.Diag(loc, diag::note_var_fixit_add_initialization) << VD->getDeclName()
450      << FixItHint::CreateInsertion(loc, initialization);
451    return true;
452  }
453  return false;
454}
455
456/// DiagnoseUninitializedUse -- Helper function for diagnosing uses of an
457/// uninitialized variable. This manages the different forms of diagnostic
458/// emitted for particular types of uses. Returns true if the use was diagnosed
459/// as a warning. If a pariticular use is one we omit warnings for, returns
460/// false.
461static bool DiagnoseUninitializedUse(Sema &S, const VarDecl *VD,
462                                     const Expr *E, bool isAlwaysUninit,
463                                     bool alwaysReportSelfInit = false) {
464  bool isSelfInit = false;
465
466  if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E)) {
467    if (isAlwaysUninit) {
468      // Inspect the initializer of the variable declaration which is
469      // being referenced prior to its initialization. We emit
470      // specialized diagnostics for self-initialization, and we
471      // specifically avoid warning about self references which take the
472      // form of:
473      //
474      //   int x = x;
475      //
476      // This is used to indicate to GCC that 'x' is intentionally left
477      // uninitialized. Proven code paths which access 'x' in
478      // an uninitialized state after this will still warn.
479      //
480      // TODO: Should we suppress maybe-uninitialized warnings for
481      // variables initialized in this way?
482      if (const Expr *Initializer = VD->getInit()) {
483        if (!alwaysReportSelfInit && DRE == Initializer->IgnoreParenImpCasts())
484          return false;
485
486        ContainsReference CR(S.Context, DRE);
487        CR.Visit(const_cast<Expr*>(Initializer));
488        isSelfInit = CR.doesContainReference();
489      }
490      if (isSelfInit) {
491        S.Diag(DRE->getLocStart(),
492               diag::warn_uninit_self_reference_in_init)
493        << VD->getDeclName() << VD->getLocation() << DRE->getSourceRange();
494      } else {
495        S.Diag(DRE->getLocStart(), diag::warn_uninit_var)
496          << VD->getDeclName() << DRE->getSourceRange();
497      }
498    } else {
499      S.Diag(DRE->getLocStart(), diag::warn_maybe_uninit_var)
500        << VD->getDeclName() << DRE->getSourceRange();
501    }
502  } else {
503    const BlockExpr *BE = cast<BlockExpr>(E);
504    S.Diag(BE->getLocStart(),
505           isAlwaysUninit ? diag::warn_uninit_var_captured_by_block
506                          : diag::warn_maybe_uninit_var_captured_by_block)
507      << VD->getDeclName();
508  }
509
510  // Report where the variable was declared when the use wasn't within
511  // the initializer of that declaration & we didn't already suggest
512  // an initialization fixit.
513  if (!isSelfInit && !SuggestInitializationFixit(S, VD))
514    S.Diag(VD->getLocStart(), diag::note_uninit_var_def)
515      << VD->getDeclName();
516
517  return true;
518}
519
520typedef std::pair<const Expr*, bool> UninitUse;
521
522namespace {
523struct SLocSort {
524  bool operator()(const UninitUse &a, const UninitUse &b) {
525    SourceLocation aLoc = a.first->getLocStart();
526    SourceLocation bLoc = b.first->getLocStart();
527    return aLoc.getRawEncoding() < bLoc.getRawEncoding();
528  }
529};
530
531class UninitValsDiagReporter : public UninitVariablesHandler {
532  Sema &S;
533  typedef SmallVector<UninitUse, 2> UsesVec;
534  typedef llvm::DenseMap<const VarDecl *, std::pair<UsesVec*, bool> > UsesMap;
535  UsesMap *uses;
536
537public:
538  UninitValsDiagReporter(Sema &S) : S(S), uses(0) {}
539  ~UninitValsDiagReporter() {
540    flushDiagnostics();
541  }
542
543  std::pair<UsesVec*, bool> &getUses(const VarDecl *vd) {
544    if (!uses)
545      uses = new UsesMap();
546
547    UsesMap::mapped_type &V = (*uses)[vd];
548    UsesVec *&vec = V.first;
549    if (!vec)
550      vec = new UsesVec();
551
552    return V;
553  }
554
555  void handleUseOfUninitVariable(const Expr *ex, const VarDecl *vd,
556                                 bool isAlwaysUninit) {
557    getUses(vd).first->push_back(std::make_pair(ex, isAlwaysUninit));
558  }
559
560  void handleSelfInit(const VarDecl *vd) {
561    getUses(vd).second = true;
562  }
563
564  void flushDiagnostics() {
565    if (!uses)
566      return;
567
568    for (UsesMap::iterator i = uses->begin(), e = uses->end(); i != e; ++i) {
569      const VarDecl *vd = i->first;
570      const UsesMap::mapped_type &V = i->second;
571
572      UsesVec *vec = V.first;
573      bool hasSelfInit = V.second;
574
575      // Specially handle the case where we have uses of an uninitialized
576      // variable, but the root cause is an idiomatic self-init.  We want
577      // to report the diagnostic at the self-init since that is the root cause.
578      if (!vec->empty() && hasSelfInit && hasAlwaysUninitializedUse(vec))
579        DiagnoseUninitializedUse(S, vd, vd->getInit()->IgnoreParenCasts(),
580                                 /* isAlwaysUninit */ true,
581                                 /* alwaysReportSelfInit */ true);
582      else {
583        // Sort the uses by their SourceLocations.  While not strictly
584        // guaranteed to produce them in line/column order, this will provide
585        // a stable ordering.
586        std::sort(vec->begin(), vec->end(), SLocSort());
587
588        for (UsesVec::iterator vi = vec->begin(), ve = vec->end(); vi != ve;
589             ++vi) {
590          if (DiagnoseUninitializedUse(S, vd, vi->first,
591                                        /*isAlwaysUninit=*/vi->second))
592            // Skip further diagnostics for this variable. We try to warn only
593            // on the first point at which a variable is used uninitialized.
594            break;
595        }
596      }
597
598      // Release the uses vector.
599      delete vec;
600    }
601    delete uses;
602  }
603
604private:
605  static bool hasAlwaysUninitializedUse(const UsesVec* vec) {
606  for (UsesVec::const_iterator i = vec->begin(), e = vec->end(); i != e; ++i) {
607    if (i->second) {
608      return true;
609    }
610  }
611  return false;
612}
613};
614}
615
616
617//===----------------------------------------------------------------------===//
618// -Wthread-safety
619//===----------------------------------------------------------------------===//
620namespace clang {
621namespace thread_safety {
622typedef std::pair<SourceLocation, PartialDiagnostic> DelayedDiag;
623typedef llvm::SmallVector<DelayedDiag, 4> DiagList;
624
625struct SortDiagBySourceLocation {
626  Sema &S;
627  SortDiagBySourceLocation(Sema &S) : S(S) {}
628
629  bool operator()(const DelayedDiag &left, const DelayedDiag &right) {
630    // Although this call will be slow, this is only called when outputting
631    // multiple warnings.
632    return S.getSourceManager().isBeforeInTranslationUnit(left.first,
633                                                          right.first);
634  }
635};
636
637namespace {
638class ThreadSafetyReporter : public clang::thread_safety::ThreadSafetyHandler {
639  Sema &S;
640  DiagList Warnings;
641  SourceLocation FunLocation;
642
643  // Helper functions
644  void warnLockMismatch(unsigned DiagID, Name LockName, SourceLocation Loc) {
645    // Gracefully handle rare cases when the analysis can't get a more
646    // precise source location.
647    if (!Loc.isValid())
648      Loc = FunLocation;
649    PartialDiagnostic Warning = S.PDiag(DiagID) << LockName;
650    Warnings.push_back(DelayedDiag(Loc, Warning));
651  }
652
653 public:
654  ThreadSafetyReporter(Sema &S, SourceLocation FL)
655    : S(S), FunLocation(FL) {}
656
657  /// \brief Emit all buffered diagnostics in order of sourcelocation.
658  /// We need to output diagnostics produced while iterating through
659  /// the lockset in deterministic order, so this function orders diagnostics
660  /// and outputs them.
661  void emitDiagnostics() {
662    SortDiagBySourceLocation SortDiagBySL(S);
663    sort(Warnings.begin(), Warnings.end(), SortDiagBySL);
664    for (DiagList::iterator I = Warnings.begin(), E = Warnings.end();
665         I != E; ++I)
666      S.Diag(I->first, I->second);
667  }
668
669  void handleInvalidLockExp(SourceLocation Loc) {
670    PartialDiagnostic Warning = S.PDiag(diag::warn_cannot_resolve_lock) << Loc;
671    Warnings.push_back(DelayedDiag(Loc, Warning));
672  }
673  void handleUnmatchedUnlock(Name LockName, SourceLocation Loc) {
674    warnLockMismatch(diag::warn_unlock_but_no_lock, LockName, Loc);
675  }
676
677  void handleDoubleLock(Name LockName, SourceLocation Loc) {
678    warnLockMismatch(diag::warn_double_lock, LockName, Loc);
679  }
680
681  void handleMutexHeldEndOfScope(Name LockName, SourceLocation Loc,
682                                 LockErrorKind LEK){
683    unsigned DiagID = 0;
684    switch (LEK) {
685      case LEK_LockedSomePredecessors:
686        DiagID = diag::warn_lock_at_end_of_scope;
687        break;
688      case LEK_LockedSomeLoopIterations:
689        DiagID = diag::warn_expecting_lock_held_on_loop;
690        break;
691      case LEK_LockedAtEndOfFunction:
692        DiagID = diag::warn_no_unlock;
693        break;
694    }
695    warnLockMismatch(DiagID, LockName, Loc);
696  }
697
698
699  void handleExclusiveAndShared(Name LockName, SourceLocation Loc1,
700                                SourceLocation Loc2) {
701    PartialDiagnostic Warning =
702      S.PDiag(diag::warn_lock_exclusive_and_shared) << LockName;
703    PartialDiagnostic Note =
704      S.PDiag(diag::note_lock_exclusive_and_shared) << LockName;
705    Warnings.push_back(DelayedDiag(Loc1, Warning));
706    Warnings.push_back(DelayedDiag(Loc2, Note));
707  }
708
709  void handleNoMutexHeld(const NamedDecl *D, ProtectedOperationKind POK,
710                         AccessKind AK, SourceLocation Loc) {
711    assert((POK == POK_VarAccess || POK == POK_VarDereference)
712             && "Only works for variables");
713    unsigned DiagID = POK == POK_VarAccess?
714                        diag::warn_variable_requires_any_lock:
715                        diag::warn_var_deref_requires_any_lock;
716    PartialDiagnostic Warning = S.PDiag(DiagID)
717      << D->getName() << getLockKindFromAccessKind(AK);
718    Warnings.push_back(DelayedDiag(Loc, Warning));
719  }
720
721  void handleMutexNotHeld(const NamedDecl *D, ProtectedOperationKind POK,
722                          Name LockName, LockKind LK, SourceLocation Loc) {
723    unsigned DiagID = 0;
724    switch (POK) {
725      case POK_VarAccess:
726        DiagID = diag::warn_variable_requires_lock;
727        break;
728      case POK_VarDereference:
729        DiagID = diag::warn_var_deref_requires_lock;
730        break;
731      case POK_FunctionCall:
732        DiagID = diag::warn_fun_requires_lock;
733        break;
734    }
735    PartialDiagnostic Warning = S.PDiag(DiagID)
736      << D->getName() << LockName << LK;
737    Warnings.push_back(DelayedDiag(Loc, Warning));
738  }
739
740  void handleFunExcludesLock(Name FunName, Name LockName, SourceLocation Loc) {
741    PartialDiagnostic Warning =
742      S.PDiag(diag::warn_fun_excludes_mutex) << FunName << LockName;
743    Warnings.push_back(DelayedDiag(Loc, Warning));
744  }
745};
746}
747}
748}
749
750//===----------------------------------------------------------------------===//
751// AnalysisBasedWarnings - Worker object used by Sema to execute analysis-based
752//  warnings on a function, method, or block.
753//===----------------------------------------------------------------------===//
754
755clang::sema::AnalysisBasedWarnings::Policy::Policy() {
756  enableCheckFallThrough = 1;
757  enableCheckUnreachable = 0;
758  enableThreadSafetyAnalysis = 0;
759}
760
761clang::sema::AnalysisBasedWarnings::AnalysisBasedWarnings(Sema &s)
762  : S(s),
763    NumFunctionsAnalyzed(0),
764    NumFunctionsWithBadCFGs(0),
765    NumCFGBlocks(0),
766    MaxCFGBlocksPerFunction(0),
767    NumUninitAnalysisFunctions(0),
768    NumUninitAnalysisVariables(0),
769    MaxUninitAnalysisVariablesPerFunction(0),
770    NumUninitAnalysisBlockVisits(0),
771    MaxUninitAnalysisBlockVisitsPerFunction(0) {
772  DiagnosticsEngine &D = S.getDiagnostics();
773  DefaultPolicy.enableCheckUnreachable = (unsigned)
774    (D.getDiagnosticLevel(diag::warn_unreachable, SourceLocation()) !=
775        DiagnosticsEngine::Ignored);
776  DefaultPolicy.enableThreadSafetyAnalysis = (unsigned)
777    (D.getDiagnosticLevel(diag::warn_double_lock, SourceLocation()) !=
778     DiagnosticsEngine::Ignored);
779
780}
781
782static void flushDiagnostics(Sema &S, sema::FunctionScopeInfo *fscope) {
783  for (SmallVectorImpl<sema::PossiblyUnreachableDiag>::iterator
784       i = fscope->PossiblyUnreachableDiags.begin(),
785       e = fscope->PossiblyUnreachableDiags.end();
786       i != e; ++i) {
787    const sema::PossiblyUnreachableDiag &D = *i;
788    S.Diag(D.Loc, D.PD);
789  }
790}
791
792void clang::sema::
793AnalysisBasedWarnings::IssueWarnings(sema::AnalysisBasedWarnings::Policy P,
794                                     sema::FunctionScopeInfo *fscope,
795                                     const Decl *D, const BlockExpr *blkExpr) {
796
797  // We avoid doing analysis-based warnings when there are errors for
798  // two reasons:
799  // (1) The CFGs often can't be constructed (if the body is invalid), so
800  //     don't bother trying.
801  // (2) The code already has problems; running the analysis just takes more
802  //     time.
803  DiagnosticsEngine &Diags = S.getDiagnostics();
804
805  // Do not do any analysis for declarations in system headers if we are
806  // going to just ignore them.
807  if (Diags.getSuppressSystemWarnings() &&
808      S.SourceMgr.isInSystemHeader(D->getLocation()))
809    return;
810
811  // For code in dependent contexts, we'll do this at instantiation time.
812  if (cast<DeclContext>(D)->isDependentContext())
813    return;
814
815  if (Diags.hasErrorOccurred() || Diags.hasFatalErrorOccurred()) {
816    // Flush out any possibly unreachable diagnostics.
817    flushDiagnostics(S, fscope);
818    return;
819  }
820
821  const Stmt *Body = D->getBody();
822  assert(Body);
823
824  AnalysisDeclContext AC(/* AnalysisDeclContextManager */ 0,  D, 0);
825
826  // Don't generate EH edges for CallExprs as we'd like to avoid the n^2
827  // explosion for destrutors that can result and the compile time hit.
828  AC.getCFGBuildOptions().PruneTriviallyFalseEdges = true;
829  AC.getCFGBuildOptions().AddEHEdges = false;
830  AC.getCFGBuildOptions().AddInitializers = true;
831  AC.getCFGBuildOptions().AddImplicitDtors = true;
832
833  // Force that certain expressions appear as CFGElements in the CFG.  This
834  // is used to speed up various analyses.
835  // FIXME: This isn't the right factoring.  This is here for initial
836  // prototyping, but we need a way for analyses to say what expressions they
837  // expect to always be CFGElements and then fill in the BuildOptions
838  // appropriately.  This is essentially a layering violation.
839  if (P.enableCheckUnreachable || P.enableThreadSafetyAnalysis) {
840    // Unreachable code analysis and thread safety require a linearized CFG.
841    AC.getCFGBuildOptions().setAllAlwaysAdd();
842  }
843  else {
844    AC.getCFGBuildOptions()
845      .setAlwaysAdd(Stmt::BinaryOperatorClass)
846      .setAlwaysAdd(Stmt::BlockExprClass)
847      .setAlwaysAdd(Stmt::CStyleCastExprClass)
848      .setAlwaysAdd(Stmt::DeclRefExprClass)
849      .setAlwaysAdd(Stmt::ImplicitCastExprClass)
850      .setAlwaysAdd(Stmt::UnaryOperatorClass);
851  }
852
853  // Construct the analysis context with the specified CFG build options.
854
855  // Emit delayed diagnostics.
856  if (!fscope->PossiblyUnreachableDiags.empty()) {
857    bool analyzed = false;
858
859    // Register the expressions with the CFGBuilder.
860    for (SmallVectorImpl<sema::PossiblyUnreachableDiag>::iterator
861         i = fscope->PossiblyUnreachableDiags.begin(),
862         e = fscope->PossiblyUnreachableDiags.end();
863         i != e; ++i) {
864      if (const Stmt *stmt = i->stmt)
865        AC.registerForcedBlockExpression(stmt);
866    }
867
868    if (AC.getCFG()) {
869      analyzed = true;
870      for (SmallVectorImpl<sema::PossiblyUnreachableDiag>::iterator
871            i = fscope->PossiblyUnreachableDiags.begin(),
872            e = fscope->PossiblyUnreachableDiags.end();
873            i != e; ++i)
874      {
875        const sema::PossiblyUnreachableDiag &D = *i;
876        bool processed = false;
877        if (const Stmt *stmt = i->stmt) {
878          const CFGBlock *block = AC.getBlockForRegisteredExpression(stmt);
879          assert(block);
880          if (CFGReverseBlockReachabilityAnalysis *cra = AC.getCFGReachablityAnalysis()) {
881            // Can this block be reached from the entrance?
882            if (cra->isReachable(&AC.getCFG()->getEntry(), block))
883              S.Diag(D.Loc, D.PD);
884            processed = true;
885          }
886        }
887        if (!processed) {
888          // Emit the warning anyway if we cannot map to a basic block.
889          S.Diag(D.Loc, D.PD);
890        }
891      }
892    }
893
894    if (!analyzed)
895      flushDiagnostics(S, fscope);
896  }
897
898
899  // Warning: check missing 'return'
900  if (P.enableCheckFallThrough) {
901    const CheckFallThroughDiagnostics &CD =
902      (isa<BlockDecl>(D) ? CheckFallThroughDiagnostics::MakeForBlock()
903                         : CheckFallThroughDiagnostics::MakeForFunction(D));
904    CheckFallThroughForBody(S, D, Body, blkExpr, CD, AC);
905  }
906
907  // Warning: check for unreachable code
908  if (P.enableCheckUnreachable) {
909    // Only check for unreachable code on non-template instantiations.
910    // Different template instantiations can effectively change the control-flow
911    // and it is very difficult to prove that a snippet of code in a template
912    // is unreachable for all instantiations.
913    bool isTemplateInstantiation = false;
914    if (const FunctionDecl *Function = dyn_cast<FunctionDecl>(D))
915      isTemplateInstantiation = Function->isTemplateInstantiation();
916    if (!isTemplateInstantiation)
917      CheckUnreachable(S, AC);
918  }
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