• Home
  • Line#
  • Scopes#
  • Navigate#
  • Raw
  • Download
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/AST/DeclCXX.h"
18 #include "clang/AST/DeclObjC.h"
19 #include "clang/AST/EvaluatedExprVisitor.h"
20 #include "clang/AST/ExprCXX.h"
21 #include "clang/AST/ExprObjC.h"
22 #include "clang/AST/ParentMap.h"
23 #include "clang/AST/RecursiveASTVisitor.h"
24 #include "clang/AST/StmtCXX.h"
25 #include "clang/AST/StmtObjC.h"
26 #include "clang/AST/StmtVisitor.h"
27 #include "clang/Analysis/Analyses/CFGReachabilityAnalysis.h"
28 #include "clang/Analysis/Analyses/Consumed.h"
29 #include "clang/Analysis/Analyses/ReachableCode.h"
30 #include "clang/Analysis/Analyses/ThreadSafety.h"
31 #include "clang/Analysis/Analyses/UninitializedValues.h"
32 #include "clang/Analysis/AnalysisContext.h"
33 #include "clang/Analysis/CFG.h"
34 #include "clang/Analysis/CFGStmtMap.h"
35 #include "clang/Basic/SourceLocation.h"
36 #include "clang/Basic/SourceManager.h"
37 #include "clang/Lex/Preprocessor.h"
38 #include "clang/Sema/ScopeInfo.h"
39 #include "clang/Sema/SemaInternal.h"
40 #include "llvm/ADT/ArrayRef.h"
41 #include "llvm/ADT/BitVector.h"
42 #include "llvm/ADT/FoldingSet.h"
43 #include "llvm/ADT/ImmutableMap.h"
44 #include "llvm/ADT/MapVector.h"
45 #include "llvm/ADT/PostOrderIterator.h"
46 #include "llvm/ADT/SmallString.h"
47 #include "llvm/ADT/SmallVector.h"
48 #include "llvm/ADT/StringRef.h"
49 #include "llvm/Support/Casting.h"
50 #include <algorithm>
51 #include <deque>
52 #include <iterator>
53 #include <vector>
54 
55 using namespace clang;
56 
57 //===----------------------------------------------------------------------===//
58 // Unreachable code analysis.
59 //===----------------------------------------------------------------------===//
60 
61 namespace {
62   class UnreachableCodeHandler : public reachable_code::Callback {
63     Sema &S;
64   public:
UnreachableCodeHandler(Sema & s)65     UnreachableCodeHandler(Sema &s) : S(s) {}
66 
HandleUnreachable(reachable_code::UnreachableKind UK,SourceLocation L,SourceRange SilenceableCondVal,SourceRange R1,SourceRange R2)67     void HandleUnreachable(reachable_code::UnreachableKind UK,
68                            SourceLocation L,
69                            SourceRange SilenceableCondVal,
70                            SourceRange R1,
71                            SourceRange R2) override {
72       unsigned diag = diag::warn_unreachable;
73       switch (UK) {
74         case reachable_code::UK_Break:
75           diag = diag::warn_unreachable_break;
76           break;
77         case reachable_code::UK_Return:
78           diag = diag::warn_unreachable_return;
79           break;
80         case reachable_code::UK_Loop_Increment:
81           diag = diag::warn_unreachable_loop_increment;
82           break;
83         case reachable_code::UK_Other:
84           break;
85       }
86 
87       S.Diag(L, diag) << R1 << R2;
88 
89       SourceLocation Open = SilenceableCondVal.getBegin();
90       if (Open.isValid()) {
91         SourceLocation Close = SilenceableCondVal.getEnd();
92         Close = S.getLocForEndOfToken(Close);
93         if (Close.isValid()) {
94           S.Diag(Open, diag::note_unreachable_silence)
95             << FixItHint::CreateInsertion(Open, "/* DISABLES CODE */ (")
96             << FixItHint::CreateInsertion(Close, ")");
97         }
98       }
99     }
100   };
101 } // anonymous namespace
102 
103 /// CheckUnreachable - Check for unreachable code.
CheckUnreachable(Sema & S,AnalysisDeclContext & AC)104 static void CheckUnreachable(Sema &S, AnalysisDeclContext &AC) {
105   // As a heuristic prune all diagnostics not in the main file.  Currently
106   // the majority of warnings in headers are false positives.  These
107   // are largely caused by configuration state, e.g. preprocessor
108   // defined code, etc.
109   //
110   // Note that this is also a performance optimization.  Analyzing
111   // headers many times can be expensive.
112   if (!S.getSourceManager().isInMainFile(AC.getDecl()->getLocStart()))
113     return;
114 
115   UnreachableCodeHandler UC(S);
116   reachable_code::FindUnreachableCode(AC, S.getPreprocessor(), UC);
117 }
118 
119 namespace {
120 /// \brief Warn on logical operator errors in CFGBuilder
121 class LogicalErrorHandler : public CFGCallback {
122   Sema &S;
123 
124 public:
LogicalErrorHandler(Sema & S)125   LogicalErrorHandler(Sema &S) : CFGCallback(), S(S) {}
126 
HasMacroID(const Expr * E)127   static bool HasMacroID(const Expr *E) {
128     if (E->getExprLoc().isMacroID())
129       return true;
130 
131     // Recurse to children.
132     for (const Stmt *SubStmt : E->children())
133       if (const Expr *SubExpr = dyn_cast_or_null<Expr>(SubStmt))
134         if (HasMacroID(SubExpr))
135           return true;
136 
137     return false;
138   }
139 
compareAlwaysTrue(const BinaryOperator * B,bool isAlwaysTrue)140   void compareAlwaysTrue(const BinaryOperator *B, bool isAlwaysTrue) override {
141     if (HasMacroID(B))
142       return;
143 
144     SourceRange DiagRange = B->getSourceRange();
145     S.Diag(B->getExprLoc(), diag::warn_tautological_overlap_comparison)
146         << DiagRange << isAlwaysTrue;
147   }
148 
compareBitwiseEquality(const BinaryOperator * B,bool isAlwaysTrue)149   void compareBitwiseEquality(const BinaryOperator *B,
150                               bool isAlwaysTrue) override {
151     if (HasMacroID(B))
152       return;
153 
154     SourceRange DiagRange = B->getSourceRange();
155     S.Diag(B->getExprLoc(), diag::warn_comparison_bitwise_always)
156         << DiagRange << isAlwaysTrue;
157   }
158 };
159 } // anonymous namespace
160 
161 //===----------------------------------------------------------------------===//
162 // Check for infinite self-recursion in functions
163 //===----------------------------------------------------------------------===//
164 
165 // Returns true if the function is called anywhere within the CFGBlock.
166 // For member functions, the additional condition of being call from the
167 // this pointer is required.
hasRecursiveCallInPath(const FunctionDecl * FD,CFGBlock & Block)168 static bool hasRecursiveCallInPath(const FunctionDecl *FD, CFGBlock &Block) {
169   // Process all the Stmt's in this block to find any calls to FD.
170   for (const auto &B : Block) {
171     if (B.getKind() != CFGElement::Statement)
172       continue;
173 
174     const CallExpr *CE = dyn_cast<CallExpr>(B.getAs<CFGStmt>()->getStmt());
175     if (!CE || !CE->getCalleeDecl() ||
176         CE->getCalleeDecl()->getCanonicalDecl() != FD)
177       continue;
178 
179     // Skip function calls which are qualified with a templated class.
180     if (const DeclRefExpr *DRE =
181             dyn_cast<DeclRefExpr>(CE->getCallee()->IgnoreParenImpCasts())) {
182       if (NestedNameSpecifier *NNS = DRE->getQualifier()) {
183         if (NNS->getKind() == NestedNameSpecifier::TypeSpec &&
184             isa<TemplateSpecializationType>(NNS->getAsType())) {
185           continue;
186         }
187       }
188     }
189 
190     const CXXMemberCallExpr *MCE = dyn_cast<CXXMemberCallExpr>(CE);
191     if (!MCE || isa<CXXThisExpr>(MCE->getImplicitObjectArgument()) ||
192         !MCE->getMethodDecl()->isVirtual())
193       return true;
194   }
195   return false;
196 }
197 
198 // All blocks are in one of three states.  States are ordered so that blocks
199 // can only move to higher states.
200 enum RecursiveState {
201   FoundNoPath,
202   FoundPath,
203   FoundPathWithNoRecursiveCall
204 };
205 
206 // Returns true if there exists a path to the exit block and every path
207 // to the exit block passes through a call to FD.
checkForRecursiveFunctionCall(const FunctionDecl * FD,CFG * cfg)208 static bool checkForRecursiveFunctionCall(const FunctionDecl *FD, CFG *cfg) {
209 
210   const unsigned ExitID = cfg->getExit().getBlockID();
211 
212   // Mark all nodes as FoundNoPath, then set the status of the entry block.
213   SmallVector<RecursiveState, 16> States(cfg->getNumBlockIDs(), FoundNoPath);
214   States[cfg->getEntry().getBlockID()] = FoundPathWithNoRecursiveCall;
215 
216   // Make the processing stack and seed it with the entry block.
217   SmallVector<CFGBlock *, 16> Stack;
218   Stack.push_back(&cfg->getEntry());
219 
220   while (!Stack.empty()) {
221     CFGBlock *CurBlock = Stack.back();
222     Stack.pop_back();
223 
224     unsigned ID = CurBlock->getBlockID();
225     RecursiveState CurState = States[ID];
226 
227     if (CurState == FoundPathWithNoRecursiveCall) {
228       // Found a path to the exit node without a recursive call.
229       if (ExitID == ID)
230         return false;
231 
232       // Only change state if the block has a recursive call.
233       if (hasRecursiveCallInPath(FD, *CurBlock))
234         CurState = FoundPath;
235     }
236 
237     // Loop over successor blocks and add them to the Stack if their state
238     // changes.
239     for (auto I = CurBlock->succ_begin(), E = CurBlock->succ_end(); I != E; ++I)
240       if (*I) {
241         unsigned next_ID = (*I)->getBlockID();
242         if (States[next_ID] < CurState) {
243           States[next_ID] = CurState;
244           Stack.push_back(*I);
245         }
246       }
247   }
248 
249   // Return true if the exit node is reachable, and only reachable through
250   // a recursive call.
251   return States[ExitID] == FoundPath;
252 }
253 
checkRecursiveFunction(Sema & S,const FunctionDecl * FD,const Stmt * Body,AnalysisDeclContext & AC)254 static void checkRecursiveFunction(Sema &S, const FunctionDecl *FD,
255                                    const Stmt *Body, AnalysisDeclContext &AC) {
256   FD = FD->getCanonicalDecl();
257 
258   // Only run on non-templated functions and non-templated members of
259   // templated classes.
260   if (FD->getTemplatedKind() != FunctionDecl::TK_NonTemplate &&
261       FD->getTemplatedKind() != FunctionDecl::TK_MemberSpecialization)
262     return;
263 
264   CFG *cfg = AC.getCFG();
265   if (!cfg) return;
266 
267   // If the exit block is unreachable, skip processing the function.
268   if (cfg->getExit().pred_empty())
269     return;
270 
271   // Emit diagnostic if a recursive function call is detected for all paths.
272   if (checkForRecursiveFunctionCall(FD, cfg))
273     S.Diag(Body->getLocStart(), diag::warn_infinite_recursive_function);
274 }
275 
276 //===----------------------------------------------------------------------===//
277 // Check for missing return value.
278 //===----------------------------------------------------------------------===//
279 
280 enum ControlFlowKind {
281   UnknownFallThrough,
282   NeverFallThrough,
283   MaybeFallThrough,
284   AlwaysFallThrough,
285   NeverFallThroughOrReturn
286 };
287 
288 /// CheckFallThrough - Check that we don't fall off the end of a
289 /// Statement that should return a value.
290 ///
291 /// \returns AlwaysFallThrough iff we always fall off the end of the statement,
292 /// MaybeFallThrough iff we might or might not fall off the end,
293 /// NeverFallThroughOrReturn iff we never fall off the end of the statement or
294 /// return.  We assume NeverFallThrough iff we never fall off the end of the
295 /// statement but we may return.  We assume that functions not marked noreturn
296 /// will return.
CheckFallThrough(AnalysisDeclContext & AC)297 static ControlFlowKind CheckFallThrough(AnalysisDeclContext &AC) {
298   CFG *cfg = AC.getCFG();
299   if (!cfg) return UnknownFallThrough;
300 
301   // The CFG leaves in dead things, and we don't want the dead code paths to
302   // confuse us, so we mark all live things first.
303   llvm::BitVector live(cfg->getNumBlockIDs());
304   unsigned count = reachable_code::ScanReachableFromBlock(&cfg->getEntry(),
305                                                           live);
306 
307   bool AddEHEdges = AC.getAddEHEdges();
308   if (!AddEHEdges && count != cfg->getNumBlockIDs())
309     // When there are things remaining dead, and we didn't add EH edges
310     // from CallExprs to the catch clauses, we have to go back and
311     // mark them as live.
312     for (const auto *B : *cfg) {
313       if (!live[B->getBlockID()]) {
314         if (B->pred_begin() == B->pred_end()) {
315           if (B->getTerminator() && isa<CXXTryStmt>(B->getTerminator()))
316             // When not adding EH edges from calls, catch clauses
317             // can otherwise seem dead.  Avoid noting them as dead.
318             count += reachable_code::ScanReachableFromBlock(B, live);
319           continue;
320         }
321       }
322     }
323 
324   // Now we know what is live, we check the live precessors of the exit block
325   // and look for fall through paths, being careful to ignore normal returns,
326   // and exceptional paths.
327   bool HasLiveReturn = false;
328   bool HasFakeEdge = false;
329   bool HasPlainEdge = false;
330   bool HasAbnormalEdge = false;
331 
332   // Ignore default cases that aren't likely to be reachable because all
333   // enums in a switch(X) have explicit case statements.
334   CFGBlock::FilterOptions FO;
335   FO.IgnoreDefaultsWithCoveredEnums = 1;
336 
337   for (CFGBlock::filtered_pred_iterator
338 	 I = cfg->getExit().filtered_pred_start_end(FO); I.hasMore(); ++I) {
339     const CFGBlock& B = **I;
340     if (!live[B.getBlockID()])
341       continue;
342 
343     // Skip blocks which contain an element marked as no-return. They don't
344     // represent actually viable edges into the exit block, so mark them as
345     // abnormal.
346     if (B.hasNoReturnElement()) {
347       HasAbnormalEdge = true;
348       continue;
349     }
350 
351     // Destructors can appear after the 'return' in the CFG.  This is
352     // normal.  We need to look pass the destructors for the return
353     // statement (if it exists).
354     CFGBlock::const_reverse_iterator ri = B.rbegin(), re = B.rend();
355 
356     for ( ; ri != re ; ++ri)
357       if (ri->getAs<CFGStmt>())
358         break;
359 
360     // No more CFGElements in the block?
361     if (ri == re) {
362       if (B.getTerminator() && isa<CXXTryStmt>(B.getTerminator())) {
363         HasAbnormalEdge = true;
364         continue;
365       }
366       // A labeled empty statement, or the entry block...
367       HasPlainEdge = true;
368       continue;
369     }
370 
371     CFGStmt CS = ri->castAs<CFGStmt>();
372     const Stmt *S = CS.getStmt();
373     if (isa<ReturnStmt>(S)) {
374       HasLiveReturn = true;
375       continue;
376     }
377     if (isa<ObjCAtThrowStmt>(S)) {
378       HasFakeEdge = true;
379       continue;
380     }
381     if (isa<CXXThrowExpr>(S)) {
382       HasFakeEdge = true;
383       continue;
384     }
385     if (isa<MSAsmStmt>(S)) {
386       // TODO: Verify this is correct.
387       HasFakeEdge = true;
388       HasLiveReturn = true;
389       continue;
390     }
391     if (isa<CXXTryStmt>(S)) {
392       HasAbnormalEdge = true;
393       continue;
394     }
395     if (std::find(B.succ_begin(), B.succ_end(), &cfg->getExit())
396         == B.succ_end()) {
397       HasAbnormalEdge = true;
398       continue;
399     }
400 
401     HasPlainEdge = true;
402   }
403   if (!HasPlainEdge) {
404     if (HasLiveReturn)
405       return NeverFallThrough;
406     return NeverFallThroughOrReturn;
407   }
408   if (HasAbnormalEdge || HasFakeEdge || HasLiveReturn)
409     return MaybeFallThrough;
410   // This says AlwaysFallThrough for calls to functions that are not marked
411   // noreturn, that don't return.  If people would like this warning to be more
412   // accurate, such functions should be marked as noreturn.
413   return AlwaysFallThrough;
414 }
415 
416 namespace {
417 
418 struct CheckFallThroughDiagnostics {
419   unsigned diag_MaybeFallThrough_HasNoReturn;
420   unsigned diag_MaybeFallThrough_ReturnsNonVoid;
421   unsigned diag_AlwaysFallThrough_HasNoReturn;
422   unsigned diag_AlwaysFallThrough_ReturnsNonVoid;
423   unsigned diag_NeverFallThroughOrReturn;
424   enum { Function, Block, Lambda } funMode;
425   SourceLocation FuncLoc;
426 
MakeForFunction__anon6dec69460311::CheckFallThroughDiagnostics427   static CheckFallThroughDiagnostics MakeForFunction(const Decl *Func) {
428     CheckFallThroughDiagnostics D;
429     D.FuncLoc = Func->getLocation();
430     D.diag_MaybeFallThrough_HasNoReturn =
431       diag::warn_falloff_noreturn_function;
432     D.diag_MaybeFallThrough_ReturnsNonVoid =
433       diag::warn_maybe_falloff_nonvoid_function;
434     D.diag_AlwaysFallThrough_HasNoReturn =
435       diag::warn_falloff_noreturn_function;
436     D.diag_AlwaysFallThrough_ReturnsNonVoid =
437       diag::warn_falloff_nonvoid_function;
438 
439     // Don't suggest that virtual functions be marked "noreturn", since they
440     // might be overridden by non-noreturn functions.
441     bool isVirtualMethod = false;
442     if (const CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(Func))
443       isVirtualMethod = Method->isVirtual();
444 
445     // Don't suggest that template instantiations be marked "noreturn"
446     bool isTemplateInstantiation = false;
447     if (const FunctionDecl *Function = dyn_cast<FunctionDecl>(Func))
448       isTemplateInstantiation = Function->isTemplateInstantiation();
449 
450     if (!isVirtualMethod && !isTemplateInstantiation)
451       D.diag_NeverFallThroughOrReturn =
452         diag::warn_suggest_noreturn_function;
453     else
454       D.diag_NeverFallThroughOrReturn = 0;
455 
456     D.funMode = Function;
457     return D;
458   }
459 
MakeForBlock__anon6dec69460311::CheckFallThroughDiagnostics460   static CheckFallThroughDiagnostics MakeForBlock() {
461     CheckFallThroughDiagnostics D;
462     D.diag_MaybeFallThrough_HasNoReturn =
463       diag::err_noreturn_block_has_return_expr;
464     D.diag_MaybeFallThrough_ReturnsNonVoid =
465       diag::err_maybe_falloff_nonvoid_block;
466     D.diag_AlwaysFallThrough_HasNoReturn =
467       diag::err_noreturn_block_has_return_expr;
468     D.diag_AlwaysFallThrough_ReturnsNonVoid =
469       diag::err_falloff_nonvoid_block;
470     D.diag_NeverFallThroughOrReturn = 0;
471     D.funMode = Block;
472     return D;
473   }
474 
MakeForLambda__anon6dec69460311::CheckFallThroughDiagnostics475   static CheckFallThroughDiagnostics MakeForLambda() {
476     CheckFallThroughDiagnostics D;
477     D.diag_MaybeFallThrough_HasNoReturn =
478       diag::err_noreturn_lambda_has_return_expr;
479     D.diag_MaybeFallThrough_ReturnsNonVoid =
480       diag::warn_maybe_falloff_nonvoid_lambda;
481     D.diag_AlwaysFallThrough_HasNoReturn =
482       diag::err_noreturn_lambda_has_return_expr;
483     D.diag_AlwaysFallThrough_ReturnsNonVoid =
484       diag::warn_falloff_nonvoid_lambda;
485     D.diag_NeverFallThroughOrReturn = 0;
486     D.funMode = Lambda;
487     return D;
488   }
489 
checkDiagnostics__anon6dec69460311::CheckFallThroughDiagnostics490   bool checkDiagnostics(DiagnosticsEngine &D, bool ReturnsVoid,
491                         bool HasNoReturn) const {
492     if (funMode == Function) {
493       return (ReturnsVoid ||
494               D.isIgnored(diag::warn_maybe_falloff_nonvoid_function,
495                           FuncLoc)) &&
496              (!HasNoReturn ||
497               D.isIgnored(diag::warn_noreturn_function_has_return_expr,
498                           FuncLoc)) &&
499              (!ReturnsVoid ||
500               D.isIgnored(diag::warn_suggest_noreturn_block, FuncLoc));
501     }
502 
503     // For blocks / lambdas.
504     return ReturnsVoid && !HasNoReturn;
505   }
506 };
507 
508 } // anonymous namespace
509 
510 /// CheckFallThroughForFunctionDef - Check that we don't fall off the end of a
511 /// function that should return a value.  Check that we don't fall off the end
512 /// of a noreturn function.  We assume that functions and blocks not marked
513 /// noreturn will return.
CheckFallThroughForBody(Sema & S,const Decl * D,const Stmt * Body,const BlockExpr * blkExpr,const CheckFallThroughDiagnostics & CD,AnalysisDeclContext & AC)514 static void CheckFallThroughForBody(Sema &S, const Decl *D, const Stmt *Body,
515                                     const BlockExpr *blkExpr,
516                                     const CheckFallThroughDiagnostics& CD,
517                                     AnalysisDeclContext &AC) {
518 
519   bool ReturnsVoid = false;
520   bool HasNoReturn = false;
521 
522   if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
523     ReturnsVoid = FD->getReturnType()->isVoidType();
524     HasNoReturn = FD->isNoReturn();
525   }
526   else if (const ObjCMethodDecl *MD = dyn_cast<ObjCMethodDecl>(D)) {
527     ReturnsVoid = MD->getReturnType()->isVoidType();
528     HasNoReturn = MD->hasAttr<NoReturnAttr>();
529   }
530   else if (isa<BlockDecl>(D)) {
531     QualType BlockTy = blkExpr->getType();
532     if (const FunctionType *FT =
533           BlockTy->getPointeeType()->getAs<FunctionType>()) {
534       if (FT->getReturnType()->isVoidType())
535         ReturnsVoid = true;
536       if (FT->getNoReturnAttr())
537         HasNoReturn = true;
538     }
539   }
540 
541   DiagnosticsEngine &Diags = S.getDiagnostics();
542 
543   // Short circuit for compilation speed.
544   if (CD.checkDiagnostics(Diags, ReturnsVoid, HasNoReturn))
545       return;
546 
547   SourceLocation LBrace = Body->getLocStart(), RBrace = Body->getLocEnd();
548   // Either in a function body compound statement, or a function-try-block.
549   switch (CheckFallThrough(AC)) {
550     case UnknownFallThrough:
551       break;
552 
553     case MaybeFallThrough:
554       if (HasNoReturn)
555         S.Diag(RBrace, CD.diag_MaybeFallThrough_HasNoReturn);
556       else if (!ReturnsVoid)
557         S.Diag(RBrace, CD.diag_MaybeFallThrough_ReturnsNonVoid);
558       break;
559     case AlwaysFallThrough:
560       if (HasNoReturn)
561         S.Diag(RBrace, CD.diag_AlwaysFallThrough_HasNoReturn);
562       else if (!ReturnsVoid)
563         S.Diag(RBrace, CD.diag_AlwaysFallThrough_ReturnsNonVoid);
564       break;
565     case NeverFallThroughOrReturn:
566       if (ReturnsVoid && !HasNoReturn && CD.diag_NeverFallThroughOrReturn) {
567         if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
568           S.Diag(LBrace, CD.diag_NeverFallThroughOrReturn) << 0 << FD;
569         } else if (const ObjCMethodDecl *MD = dyn_cast<ObjCMethodDecl>(D)) {
570           S.Diag(LBrace, CD.diag_NeverFallThroughOrReturn) << 1 << MD;
571         } else {
572           S.Diag(LBrace, CD.diag_NeverFallThroughOrReturn);
573         }
574       }
575       break;
576     case NeverFallThrough:
577       break;
578   }
579 }
580 
581 //===----------------------------------------------------------------------===//
582 // -Wuninitialized
583 //===----------------------------------------------------------------------===//
584 
585 namespace {
586 /// ContainsReference - A visitor class to search for references to
587 /// a particular declaration (the needle) within any evaluated component of an
588 /// expression (recursively).
589 class ContainsReference : public ConstEvaluatedExprVisitor<ContainsReference> {
590   bool FoundReference;
591   const DeclRefExpr *Needle;
592 
593 public:
594   typedef ConstEvaluatedExprVisitor<ContainsReference> Inherited;
595 
ContainsReference(ASTContext & Context,const DeclRefExpr * Needle)596   ContainsReference(ASTContext &Context, const DeclRefExpr *Needle)
597     : Inherited(Context), FoundReference(false), Needle(Needle) {}
598 
VisitExpr(const Expr * E)599   void VisitExpr(const Expr *E) {
600     // Stop evaluating if we already have a reference.
601     if (FoundReference)
602       return;
603 
604     Inherited::VisitExpr(E);
605   }
606 
VisitDeclRefExpr(const DeclRefExpr * E)607   void VisitDeclRefExpr(const DeclRefExpr *E) {
608     if (E == Needle)
609       FoundReference = true;
610     else
611       Inherited::VisitDeclRefExpr(E);
612   }
613 
doesContainReference() const614   bool doesContainReference() const { return FoundReference; }
615 };
616 } // anonymous namespace
617 
SuggestInitializationFixit(Sema & S,const VarDecl * VD)618 static bool SuggestInitializationFixit(Sema &S, const VarDecl *VD) {
619   QualType VariableTy = VD->getType().getCanonicalType();
620   if (VariableTy->isBlockPointerType() &&
621       !VD->hasAttr<BlocksAttr>()) {
622     S.Diag(VD->getLocation(), diag::note_block_var_fixit_add_initialization)
623         << VD->getDeclName()
624         << FixItHint::CreateInsertion(VD->getLocation(), "__block ");
625     return true;
626   }
627 
628   // Don't issue a fixit if there is already an initializer.
629   if (VD->getInit())
630     return false;
631 
632   // Don't suggest a fixit inside macros.
633   if (VD->getLocEnd().isMacroID())
634     return false;
635 
636   SourceLocation Loc = S.getLocForEndOfToken(VD->getLocEnd());
637 
638   // Suggest possible initialization (if any).
639   std::string Init = S.getFixItZeroInitializerForType(VariableTy, Loc);
640   if (Init.empty())
641     return false;
642 
643   S.Diag(Loc, diag::note_var_fixit_add_initialization) << VD->getDeclName()
644     << FixItHint::CreateInsertion(Loc, Init);
645   return true;
646 }
647 
648 /// Create a fixit to remove an if-like statement, on the assumption that its
649 /// condition is CondVal.
CreateIfFixit(Sema & S,const Stmt * If,const Stmt * Then,const Stmt * Else,bool CondVal,FixItHint & Fixit1,FixItHint & Fixit2)650 static void CreateIfFixit(Sema &S, const Stmt *If, const Stmt *Then,
651                           const Stmt *Else, bool CondVal,
652                           FixItHint &Fixit1, FixItHint &Fixit2) {
653   if (CondVal) {
654     // If condition is always true, remove all but the 'then'.
655     Fixit1 = FixItHint::CreateRemoval(
656         CharSourceRange::getCharRange(If->getLocStart(),
657                                       Then->getLocStart()));
658     if (Else) {
659       SourceLocation ElseKwLoc = S.getLocForEndOfToken(Then->getLocEnd());
660       Fixit2 = FixItHint::CreateRemoval(
661           SourceRange(ElseKwLoc, Else->getLocEnd()));
662     }
663   } else {
664     // If condition is always false, remove all but the 'else'.
665     if (Else)
666       Fixit1 = FixItHint::CreateRemoval(
667           CharSourceRange::getCharRange(If->getLocStart(),
668                                         Else->getLocStart()));
669     else
670       Fixit1 = FixItHint::CreateRemoval(If->getSourceRange());
671   }
672 }
673 
674 /// DiagUninitUse -- Helper function to produce a diagnostic for an
675 /// uninitialized use of a variable.
DiagUninitUse(Sema & S,const VarDecl * VD,const UninitUse & Use,bool IsCapturedByBlock)676 static void DiagUninitUse(Sema &S, const VarDecl *VD, const UninitUse &Use,
677                           bool IsCapturedByBlock) {
678   bool Diagnosed = false;
679 
680   switch (Use.getKind()) {
681   case UninitUse::Always:
682     S.Diag(Use.getUser()->getLocStart(), diag::warn_uninit_var)
683         << VD->getDeclName() << IsCapturedByBlock
684         << Use.getUser()->getSourceRange();
685     return;
686 
687   case UninitUse::AfterDecl:
688   case UninitUse::AfterCall:
689     S.Diag(VD->getLocation(), diag::warn_sometimes_uninit_var)
690       << VD->getDeclName() << IsCapturedByBlock
691       << (Use.getKind() == UninitUse::AfterDecl ? 4 : 5)
692       << const_cast<DeclContext*>(VD->getLexicalDeclContext())
693       << VD->getSourceRange();
694     S.Diag(Use.getUser()->getLocStart(), diag::note_uninit_var_use)
695       << IsCapturedByBlock << Use.getUser()->getSourceRange();
696     return;
697 
698   case UninitUse::Maybe:
699   case UninitUse::Sometimes:
700     // Carry on to report sometimes-uninitialized branches, if possible,
701     // or a 'may be used uninitialized' diagnostic otherwise.
702     break;
703   }
704 
705   // Diagnose each branch which leads to a sometimes-uninitialized use.
706   for (UninitUse::branch_iterator I = Use.branch_begin(), E = Use.branch_end();
707        I != E; ++I) {
708     assert(Use.getKind() == UninitUse::Sometimes);
709 
710     const Expr *User = Use.getUser();
711     const Stmt *Term = I->Terminator;
712 
713     // Information used when building the diagnostic.
714     unsigned DiagKind;
715     StringRef Str;
716     SourceRange Range;
717 
718     // FixIts to suppress the diagnostic by removing the dead condition.
719     // For all binary terminators, branch 0 is taken if the condition is true,
720     // and branch 1 is taken if the condition is false.
721     int RemoveDiagKind = -1;
722     const char *FixitStr =
723         S.getLangOpts().CPlusPlus ? (I->Output ? "true" : "false")
724                                   : (I->Output ? "1" : "0");
725     FixItHint Fixit1, Fixit2;
726 
727     switch (Term ? Term->getStmtClass() : Stmt::DeclStmtClass) {
728     default:
729       // Don't know how to report this. Just fall back to 'may be used
730       // uninitialized'. FIXME: Can this happen?
731       continue;
732 
733     // "condition is true / condition is false".
734     case Stmt::IfStmtClass: {
735       const IfStmt *IS = cast<IfStmt>(Term);
736       DiagKind = 0;
737       Str = "if";
738       Range = IS->getCond()->getSourceRange();
739       RemoveDiagKind = 0;
740       CreateIfFixit(S, IS, IS->getThen(), IS->getElse(),
741                     I->Output, Fixit1, Fixit2);
742       break;
743     }
744     case Stmt::ConditionalOperatorClass: {
745       const ConditionalOperator *CO = cast<ConditionalOperator>(Term);
746       DiagKind = 0;
747       Str = "?:";
748       Range = CO->getCond()->getSourceRange();
749       RemoveDiagKind = 0;
750       CreateIfFixit(S, CO, CO->getTrueExpr(), CO->getFalseExpr(),
751                     I->Output, Fixit1, Fixit2);
752       break;
753     }
754     case Stmt::BinaryOperatorClass: {
755       const BinaryOperator *BO = cast<BinaryOperator>(Term);
756       if (!BO->isLogicalOp())
757         continue;
758       DiagKind = 0;
759       Str = BO->getOpcodeStr();
760       Range = BO->getLHS()->getSourceRange();
761       RemoveDiagKind = 0;
762       if ((BO->getOpcode() == BO_LAnd && I->Output) ||
763           (BO->getOpcode() == BO_LOr && !I->Output))
764         // true && y -> y, false || y -> y.
765         Fixit1 = FixItHint::CreateRemoval(SourceRange(BO->getLocStart(),
766                                                       BO->getOperatorLoc()));
767       else
768         // false && y -> false, true || y -> true.
769         Fixit1 = FixItHint::CreateReplacement(BO->getSourceRange(), FixitStr);
770       break;
771     }
772 
773     // "loop is entered / loop is exited".
774     case Stmt::WhileStmtClass:
775       DiagKind = 1;
776       Str = "while";
777       Range = cast<WhileStmt>(Term)->getCond()->getSourceRange();
778       RemoveDiagKind = 1;
779       Fixit1 = FixItHint::CreateReplacement(Range, FixitStr);
780       break;
781     case Stmt::ForStmtClass:
782       DiagKind = 1;
783       Str = "for";
784       Range = cast<ForStmt>(Term)->getCond()->getSourceRange();
785       RemoveDiagKind = 1;
786       if (I->Output)
787         Fixit1 = FixItHint::CreateRemoval(Range);
788       else
789         Fixit1 = FixItHint::CreateReplacement(Range, FixitStr);
790       break;
791     case Stmt::CXXForRangeStmtClass:
792       if (I->Output == 1) {
793         // The use occurs if a range-based for loop's body never executes.
794         // That may be impossible, and there's no syntactic fix for this,
795         // so treat it as a 'may be uninitialized' case.
796         continue;
797       }
798       DiagKind = 1;
799       Str = "for";
800       Range = cast<CXXForRangeStmt>(Term)->getRangeInit()->getSourceRange();
801       break;
802 
803     // "condition is true / loop is exited".
804     case Stmt::DoStmtClass:
805       DiagKind = 2;
806       Str = "do";
807       Range = cast<DoStmt>(Term)->getCond()->getSourceRange();
808       RemoveDiagKind = 1;
809       Fixit1 = FixItHint::CreateReplacement(Range, FixitStr);
810       break;
811 
812     // "switch case is taken".
813     case Stmt::CaseStmtClass:
814       DiagKind = 3;
815       Str = "case";
816       Range = cast<CaseStmt>(Term)->getLHS()->getSourceRange();
817       break;
818     case Stmt::DefaultStmtClass:
819       DiagKind = 3;
820       Str = "default";
821       Range = cast<DefaultStmt>(Term)->getDefaultLoc();
822       break;
823     }
824 
825     S.Diag(Range.getBegin(), diag::warn_sometimes_uninit_var)
826       << VD->getDeclName() << IsCapturedByBlock << DiagKind
827       << Str << I->Output << Range;
828     S.Diag(User->getLocStart(), diag::note_uninit_var_use)
829       << IsCapturedByBlock << User->getSourceRange();
830     if (RemoveDiagKind != -1)
831       S.Diag(Fixit1.RemoveRange.getBegin(), diag::note_uninit_fixit_remove_cond)
832         << RemoveDiagKind << Str << I->Output << Fixit1 << Fixit2;
833 
834     Diagnosed = true;
835   }
836 
837   if (!Diagnosed)
838     S.Diag(Use.getUser()->getLocStart(), diag::warn_maybe_uninit_var)
839         << VD->getDeclName() << IsCapturedByBlock
840         << Use.getUser()->getSourceRange();
841 }
842 
843 /// DiagnoseUninitializedUse -- Helper function for diagnosing uses of an
844 /// uninitialized variable. This manages the different forms of diagnostic
845 /// emitted for particular types of uses. Returns true if the use was diagnosed
846 /// as a warning. If a particular use is one we omit warnings for, returns
847 /// false.
DiagnoseUninitializedUse(Sema & S,const VarDecl * VD,const UninitUse & Use,bool alwaysReportSelfInit=false)848 static bool DiagnoseUninitializedUse(Sema &S, const VarDecl *VD,
849                                      const UninitUse &Use,
850                                      bool alwaysReportSelfInit = false) {
851   if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(Use.getUser())) {
852     // Inspect the initializer of the variable declaration which is
853     // being referenced prior to its initialization. We emit
854     // specialized diagnostics for self-initialization, and we
855     // specifically avoid warning about self references which take the
856     // form of:
857     //
858     //   int x = x;
859     //
860     // This is used to indicate to GCC that 'x' is intentionally left
861     // uninitialized. Proven code paths which access 'x' in
862     // an uninitialized state after this will still warn.
863     if (const Expr *Initializer = VD->getInit()) {
864       if (!alwaysReportSelfInit && DRE == Initializer->IgnoreParenImpCasts())
865         return false;
866 
867       ContainsReference CR(S.Context, DRE);
868       CR.Visit(Initializer);
869       if (CR.doesContainReference()) {
870         S.Diag(DRE->getLocStart(),
871                diag::warn_uninit_self_reference_in_init)
872           << VD->getDeclName() << VD->getLocation() << DRE->getSourceRange();
873         return true;
874       }
875     }
876 
877     DiagUninitUse(S, VD, Use, false);
878   } else {
879     const BlockExpr *BE = cast<BlockExpr>(Use.getUser());
880     if (VD->getType()->isBlockPointerType() && !VD->hasAttr<BlocksAttr>())
881       S.Diag(BE->getLocStart(),
882              diag::warn_uninit_byref_blockvar_captured_by_block)
883         << VD->getDeclName();
884     else
885       DiagUninitUse(S, VD, Use, true);
886   }
887 
888   // Report where the variable was declared when the use wasn't within
889   // the initializer of that declaration & we didn't already suggest
890   // an initialization fixit.
891   if (!SuggestInitializationFixit(S, VD))
892     S.Diag(VD->getLocStart(), diag::note_var_declared_here)
893       << VD->getDeclName();
894 
895   return true;
896 }
897 
898 namespace {
899   class FallthroughMapper : public RecursiveASTVisitor<FallthroughMapper> {
900   public:
FallthroughMapper(Sema & S)901     FallthroughMapper(Sema &S)
902       : FoundSwitchStatements(false),
903         S(S) {
904     }
905 
foundSwitchStatements() const906     bool foundSwitchStatements() const { return FoundSwitchStatements; }
907 
markFallthroughVisited(const AttributedStmt * Stmt)908     void markFallthroughVisited(const AttributedStmt *Stmt) {
909       bool Found = FallthroughStmts.erase(Stmt);
910       assert(Found);
911       (void)Found;
912     }
913 
914     typedef llvm::SmallPtrSet<const AttributedStmt*, 8> AttrStmts;
915 
getFallthroughStmts() const916     const AttrStmts &getFallthroughStmts() const {
917       return FallthroughStmts;
918     }
919 
fillReachableBlocks(CFG * Cfg)920     void fillReachableBlocks(CFG *Cfg) {
921       assert(ReachableBlocks.empty() && "ReachableBlocks already filled");
922       std::deque<const CFGBlock *> BlockQueue;
923 
924       ReachableBlocks.insert(&Cfg->getEntry());
925       BlockQueue.push_back(&Cfg->getEntry());
926       // Mark all case blocks reachable to avoid problems with switching on
927       // constants, covered enums, etc.
928       // These blocks can contain fall-through annotations, and we don't want to
929       // issue a warn_fallthrough_attr_unreachable for them.
930       for (const auto *B : *Cfg) {
931         const Stmt *L = B->getLabel();
932         if (L && isa<SwitchCase>(L) && ReachableBlocks.insert(B).second)
933           BlockQueue.push_back(B);
934       }
935 
936       while (!BlockQueue.empty()) {
937         const CFGBlock *P = BlockQueue.front();
938         BlockQueue.pop_front();
939         for (CFGBlock::const_succ_iterator I = P->succ_begin(),
940                                            E = P->succ_end();
941              I != E; ++I) {
942           if (*I && ReachableBlocks.insert(*I).second)
943             BlockQueue.push_back(*I);
944         }
945       }
946     }
947 
checkFallThroughIntoBlock(const CFGBlock & B,int & AnnotatedCnt)948     bool checkFallThroughIntoBlock(const CFGBlock &B, int &AnnotatedCnt) {
949       assert(!ReachableBlocks.empty() && "ReachableBlocks empty");
950 
951       int UnannotatedCnt = 0;
952       AnnotatedCnt = 0;
953 
954       std::deque<const CFGBlock*> BlockQueue(B.pred_begin(), B.pred_end());
955       while (!BlockQueue.empty()) {
956         const CFGBlock *P = BlockQueue.front();
957         BlockQueue.pop_front();
958         if (!P) continue;
959 
960         const Stmt *Term = P->getTerminator();
961         if (Term && isa<SwitchStmt>(Term))
962           continue; // Switch statement, good.
963 
964         const SwitchCase *SW = dyn_cast_or_null<SwitchCase>(P->getLabel());
965         if (SW && SW->getSubStmt() == B.getLabel() && P->begin() == P->end())
966           continue; // Previous case label has no statements, good.
967 
968         const LabelStmt *L = dyn_cast_or_null<LabelStmt>(P->getLabel());
969         if (L && L->getSubStmt() == B.getLabel() && P->begin() == P->end())
970           continue; // Case label is preceded with a normal label, good.
971 
972         if (!ReachableBlocks.count(P)) {
973           for (CFGBlock::const_reverse_iterator ElemIt = P->rbegin(),
974                                                 ElemEnd = P->rend();
975                ElemIt != ElemEnd; ++ElemIt) {
976             if (Optional<CFGStmt> CS = ElemIt->getAs<CFGStmt>()) {
977               if (const AttributedStmt *AS = asFallThroughAttr(CS->getStmt())) {
978                 S.Diag(AS->getLocStart(),
979                        diag::warn_fallthrough_attr_unreachable);
980                 markFallthroughVisited(AS);
981                 ++AnnotatedCnt;
982                 break;
983               }
984               // Don't care about other unreachable statements.
985             }
986           }
987           // If there are no unreachable statements, this may be a special
988           // case in CFG:
989           // case X: {
990           //    A a;  // A has a destructor.
991           //    break;
992           // }
993           // // <<<< This place is represented by a 'hanging' CFG block.
994           // case Y:
995           continue;
996         }
997 
998         const Stmt *LastStmt = getLastStmt(*P);
999         if (const AttributedStmt *AS = asFallThroughAttr(LastStmt)) {
1000           markFallthroughVisited(AS);
1001           ++AnnotatedCnt;
1002           continue; // Fallthrough annotation, good.
1003         }
1004 
1005         if (!LastStmt) { // This block contains no executable statements.
1006           // Traverse its predecessors.
1007           std::copy(P->pred_begin(), P->pred_end(),
1008                     std::back_inserter(BlockQueue));
1009           continue;
1010         }
1011 
1012         ++UnannotatedCnt;
1013       }
1014       return !!UnannotatedCnt;
1015     }
1016 
1017     // RecursiveASTVisitor setup.
shouldWalkTypesOfTypeLocs() const1018     bool shouldWalkTypesOfTypeLocs() const { return false; }
1019 
VisitAttributedStmt(AttributedStmt * S)1020     bool VisitAttributedStmt(AttributedStmt *S) {
1021       if (asFallThroughAttr(S))
1022         FallthroughStmts.insert(S);
1023       return true;
1024     }
1025 
VisitSwitchStmt(SwitchStmt * S)1026     bool VisitSwitchStmt(SwitchStmt *S) {
1027       FoundSwitchStatements = true;
1028       return true;
1029     }
1030 
1031     // We don't want to traverse local type declarations. We analyze their
1032     // methods separately.
TraverseDecl(Decl * D)1033     bool TraverseDecl(Decl *D) { return true; }
1034 
1035     // We analyze lambda bodies separately. Skip them here.
TraverseLambdaBody(LambdaExpr * LE)1036     bool TraverseLambdaBody(LambdaExpr *LE) { return true; }
1037 
1038   private:
1039 
asFallThroughAttr(const Stmt * S)1040     static const AttributedStmt *asFallThroughAttr(const Stmt *S) {
1041       if (const AttributedStmt *AS = dyn_cast_or_null<AttributedStmt>(S)) {
1042         if (hasSpecificAttr<FallThroughAttr>(AS->getAttrs()))
1043           return AS;
1044       }
1045       return nullptr;
1046     }
1047 
getLastStmt(const CFGBlock & B)1048     static const Stmt *getLastStmt(const CFGBlock &B) {
1049       if (const Stmt *Term = B.getTerminator())
1050         return Term;
1051       for (CFGBlock::const_reverse_iterator ElemIt = B.rbegin(),
1052                                             ElemEnd = B.rend();
1053                                             ElemIt != ElemEnd; ++ElemIt) {
1054         if (Optional<CFGStmt> CS = ElemIt->getAs<CFGStmt>())
1055           return CS->getStmt();
1056       }
1057       // Workaround to detect a statement thrown out by CFGBuilder:
1058       //   case X: {} case Y:
1059       //   case X: ; case Y:
1060       if (const SwitchCase *SW = dyn_cast_or_null<SwitchCase>(B.getLabel()))
1061         if (!isa<SwitchCase>(SW->getSubStmt()))
1062           return SW->getSubStmt();
1063 
1064       return nullptr;
1065     }
1066 
1067     bool FoundSwitchStatements;
1068     AttrStmts FallthroughStmts;
1069     Sema &S;
1070     llvm::SmallPtrSet<const CFGBlock *, 16> ReachableBlocks;
1071   };
1072 } // anonymous namespace
1073 
getFallthroughAttrSpelling(Preprocessor & PP,SourceLocation Loc)1074 static StringRef getFallthroughAttrSpelling(Preprocessor &PP,
1075                                             SourceLocation Loc) {
1076   TokenValue FallthroughTokens[] = {
1077     tok::l_square, tok::l_square,
1078     PP.getIdentifierInfo("fallthrough"),
1079     tok::r_square, tok::r_square
1080   };
1081 
1082   TokenValue ClangFallthroughTokens[] = {
1083     tok::l_square, tok::l_square, PP.getIdentifierInfo("clang"),
1084     tok::coloncolon, PP.getIdentifierInfo("fallthrough"),
1085     tok::r_square, tok::r_square
1086   };
1087 
1088   bool PreferClangAttr = !PP.getLangOpts().CPlusPlus1z;
1089 
1090   StringRef MacroName;
1091   if (PreferClangAttr)
1092     MacroName = PP.getLastMacroWithSpelling(Loc, ClangFallthroughTokens);
1093   if (MacroName.empty())
1094     MacroName = PP.getLastMacroWithSpelling(Loc, FallthroughTokens);
1095   if (MacroName.empty() && !PreferClangAttr)
1096     MacroName = PP.getLastMacroWithSpelling(Loc, ClangFallthroughTokens);
1097   if (MacroName.empty())
1098     MacroName = PreferClangAttr ? "[[clang::fallthrough]]" : "[[fallthrough]]";
1099   return MacroName;
1100 }
1101 
DiagnoseSwitchLabelsFallthrough(Sema & S,AnalysisDeclContext & AC,bool PerFunction)1102 static void DiagnoseSwitchLabelsFallthrough(Sema &S, AnalysisDeclContext &AC,
1103                                             bool PerFunction) {
1104   // Only perform this analysis when using C++11.  There is no good workflow
1105   // for this warning when not using C++11.  There is no good way to silence
1106   // the warning (no attribute is available) unless we are using C++11's support
1107   // for generalized attributes.  Once could use pragmas to silence the warning,
1108   // but as a general solution that is gross and not in the spirit of this
1109   // warning.
1110   //
1111   // NOTE: This an intermediate solution.  There are on-going discussions on
1112   // how to properly support this warning outside of C++11 with an annotation.
1113   if (!AC.getASTContext().getLangOpts().CPlusPlus11)
1114     return;
1115 
1116   FallthroughMapper FM(S);
1117   FM.TraverseStmt(AC.getBody());
1118 
1119   if (!FM.foundSwitchStatements())
1120     return;
1121 
1122   if (PerFunction && FM.getFallthroughStmts().empty())
1123     return;
1124 
1125   CFG *Cfg = AC.getCFG();
1126 
1127   if (!Cfg)
1128     return;
1129 
1130   FM.fillReachableBlocks(Cfg);
1131 
1132   for (const CFGBlock *B : llvm::reverse(*Cfg)) {
1133     const Stmt *Label = B->getLabel();
1134 
1135     if (!Label || !isa<SwitchCase>(Label))
1136       continue;
1137 
1138     int AnnotatedCnt;
1139 
1140     if (!FM.checkFallThroughIntoBlock(*B, AnnotatedCnt))
1141       continue;
1142 
1143     S.Diag(Label->getLocStart(),
1144         PerFunction ? diag::warn_unannotated_fallthrough_per_function
1145                     : diag::warn_unannotated_fallthrough);
1146 
1147     if (!AnnotatedCnt) {
1148       SourceLocation L = Label->getLocStart();
1149       if (L.isMacroID())
1150         continue;
1151       if (S.getLangOpts().CPlusPlus11) {
1152         const Stmt *Term = B->getTerminator();
1153         // Skip empty cases.
1154         while (B->empty() && !Term && B->succ_size() == 1) {
1155           B = *B->succ_begin();
1156           Term = B->getTerminator();
1157         }
1158         if (!(B->empty() && Term && isa<BreakStmt>(Term))) {
1159           Preprocessor &PP = S.getPreprocessor();
1160           StringRef AnnotationSpelling = getFallthroughAttrSpelling(PP, L);
1161           SmallString<64> TextToInsert(AnnotationSpelling);
1162           TextToInsert += "; ";
1163           S.Diag(L, diag::note_insert_fallthrough_fixit) <<
1164               AnnotationSpelling <<
1165               FixItHint::CreateInsertion(L, TextToInsert);
1166         }
1167       }
1168       S.Diag(L, diag::note_insert_break_fixit) <<
1169         FixItHint::CreateInsertion(L, "break; ");
1170     }
1171   }
1172 
1173   for (const auto *F : FM.getFallthroughStmts())
1174     S.Diag(F->getLocStart(), diag::err_fallthrough_attr_invalid_placement);
1175 }
1176 
isInLoop(const ASTContext & Ctx,const ParentMap & PM,const Stmt * S)1177 static bool isInLoop(const ASTContext &Ctx, const ParentMap &PM,
1178                      const Stmt *S) {
1179   assert(S);
1180 
1181   do {
1182     switch (S->getStmtClass()) {
1183     case Stmt::ForStmtClass:
1184     case Stmt::WhileStmtClass:
1185     case Stmt::CXXForRangeStmtClass:
1186     case Stmt::ObjCForCollectionStmtClass:
1187       return true;
1188     case Stmt::DoStmtClass: {
1189       const Expr *Cond = cast<DoStmt>(S)->getCond();
1190       llvm::APSInt Val;
1191       if (!Cond->EvaluateAsInt(Val, Ctx))
1192         return true;
1193       return Val.getBoolValue();
1194     }
1195     default:
1196       break;
1197     }
1198   } while ((S = PM.getParent(S)));
1199 
1200   return false;
1201 }
1202 
diagnoseRepeatedUseOfWeak(Sema & S,const sema::FunctionScopeInfo * CurFn,const Decl * D,const ParentMap & PM)1203 static void diagnoseRepeatedUseOfWeak(Sema &S,
1204                                       const sema::FunctionScopeInfo *CurFn,
1205                                       const Decl *D,
1206                                       const ParentMap &PM) {
1207   typedef sema::FunctionScopeInfo::WeakObjectProfileTy WeakObjectProfileTy;
1208   typedef sema::FunctionScopeInfo::WeakObjectUseMap WeakObjectUseMap;
1209   typedef sema::FunctionScopeInfo::WeakUseVector WeakUseVector;
1210   typedef std::pair<const Stmt *, WeakObjectUseMap::const_iterator>
1211   StmtUsesPair;
1212 
1213   ASTContext &Ctx = S.getASTContext();
1214 
1215   const WeakObjectUseMap &WeakMap = CurFn->getWeakObjectUses();
1216 
1217   // Extract all weak objects that are referenced more than once.
1218   SmallVector<StmtUsesPair, 8> UsesByStmt;
1219   for (WeakObjectUseMap::const_iterator I = WeakMap.begin(), E = WeakMap.end();
1220        I != E; ++I) {
1221     const WeakUseVector &Uses = I->second;
1222 
1223     // Find the first read of the weak object.
1224     WeakUseVector::const_iterator UI = Uses.begin(), UE = Uses.end();
1225     for ( ; UI != UE; ++UI) {
1226       if (UI->isUnsafe())
1227         break;
1228     }
1229 
1230     // If there were only writes to this object, don't warn.
1231     if (UI == UE)
1232       continue;
1233 
1234     // If there was only one read, followed by any number of writes, and the
1235     // read is not within a loop, don't warn. Additionally, don't warn in a
1236     // loop if the base object is a local variable -- local variables are often
1237     // changed in loops.
1238     if (UI == Uses.begin()) {
1239       WeakUseVector::const_iterator UI2 = UI;
1240       for (++UI2; UI2 != UE; ++UI2)
1241         if (UI2->isUnsafe())
1242           break;
1243 
1244       if (UI2 == UE) {
1245         if (!isInLoop(Ctx, PM, UI->getUseExpr()))
1246           continue;
1247 
1248         const WeakObjectProfileTy &Profile = I->first;
1249         if (!Profile.isExactProfile())
1250           continue;
1251 
1252         const NamedDecl *Base = Profile.getBase();
1253         if (!Base)
1254           Base = Profile.getProperty();
1255         assert(Base && "A profile always has a base or property.");
1256 
1257         if (const VarDecl *BaseVar = dyn_cast<VarDecl>(Base))
1258           if (BaseVar->hasLocalStorage() && !isa<ParmVarDecl>(Base))
1259             continue;
1260       }
1261     }
1262 
1263     UsesByStmt.push_back(StmtUsesPair(UI->getUseExpr(), I));
1264   }
1265 
1266   if (UsesByStmt.empty())
1267     return;
1268 
1269   // Sort by first use so that we emit the warnings in a deterministic order.
1270   SourceManager &SM = S.getSourceManager();
1271   std::sort(UsesByStmt.begin(), UsesByStmt.end(),
1272             [&SM](const StmtUsesPair &LHS, const StmtUsesPair &RHS) {
1273     return SM.isBeforeInTranslationUnit(LHS.first->getLocStart(),
1274                                         RHS.first->getLocStart());
1275   });
1276 
1277   // Classify the current code body for better warning text.
1278   // This enum should stay in sync with the cases in
1279   // warn_arc_repeated_use_of_weak and warn_arc_possible_repeated_use_of_weak.
1280   // FIXME: Should we use a common classification enum and the same set of
1281   // possibilities all throughout Sema?
1282   enum {
1283     Function,
1284     Method,
1285     Block,
1286     Lambda
1287   } FunctionKind;
1288 
1289   if (isa<sema::BlockScopeInfo>(CurFn))
1290     FunctionKind = Block;
1291   else if (isa<sema::LambdaScopeInfo>(CurFn))
1292     FunctionKind = Lambda;
1293   else if (isa<ObjCMethodDecl>(D))
1294     FunctionKind = Method;
1295   else
1296     FunctionKind = Function;
1297 
1298   // Iterate through the sorted problems and emit warnings for each.
1299   for (const auto &P : UsesByStmt) {
1300     const Stmt *FirstRead = P.first;
1301     const WeakObjectProfileTy &Key = P.second->first;
1302     const WeakUseVector &Uses = P.second->second;
1303 
1304     // For complicated expressions like 'a.b.c' and 'x.b.c', WeakObjectProfileTy
1305     // may not contain enough information to determine that these are different
1306     // properties. We can only be 100% sure of a repeated use in certain cases,
1307     // and we adjust the diagnostic kind accordingly so that the less certain
1308     // case can be turned off if it is too noisy.
1309     unsigned DiagKind;
1310     if (Key.isExactProfile())
1311       DiagKind = diag::warn_arc_repeated_use_of_weak;
1312     else
1313       DiagKind = diag::warn_arc_possible_repeated_use_of_weak;
1314 
1315     // Classify the weak object being accessed for better warning text.
1316     // This enum should stay in sync with the cases in
1317     // warn_arc_repeated_use_of_weak and warn_arc_possible_repeated_use_of_weak.
1318     enum {
1319       Variable,
1320       Property,
1321       ImplicitProperty,
1322       Ivar
1323     } ObjectKind;
1324 
1325     const NamedDecl *KeyProp = Key.getProperty();
1326     if (isa<VarDecl>(KeyProp))
1327       ObjectKind = Variable;
1328     else if (isa<ObjCPropertyDecl>(KeyProp))
1329       ObjectKind = Property;
1330     else if (isa<ObjCMethodDecl>(KeyProp))
1331       ObjectKind = ImplicitProperty;
1332     else if (isa<ObjCIvarDecl>(KeyProp))
1333       ObjectKind = Ivar;
1334     else
1335       llvm_unreachable("Unexpected weak object kind!");
1336 
1337     // Do not warn about IBOutlet weak property receivers being set to null
1338     // since they are typically only used from the main thread.
1339     if (const ObjCPropertyDecl *Prop = dyn_cast<ObjCPropertyDecl>(KeyProp))
1340       if (Prop->hasAttr<IBOutletAttr>())
1341         continue;
1342 
1343     // Show the first time the object was read.
1344     S.Diag(FirstRead->getLocStart(), DiagKind)
1345       << int(ObjectKind) << KeyProp << int(FunctionKind)
1346       << FirstRead->getSourceRange();
1347 
1348     // Print all the other accesses as notes.
1349     for (const auto &Use : Uses) {
1350       if (Use.getUseExpr() == FirstRead)
1351         continue;
1352       S.Diag(Use.getUseExpr()->getLocStart(),
1353              diag::note_arc_weak_also_accessed_here)
1354           << Use.getUseExpr()->getSourceRange();
1355     }
1356   }
1357 }
1358 
1359 namespace {
1360 class UninitValsDiagReporter : public UninitVariablesHandler {
1361   Sema &S;
1362   typedef SmallVector<UninitUse, 2> UsesVec;
1363   typedef llvm::PointerIntPair<UsesVec *, 1, bool> MappedType;
1364   // Prefer using MapVector to DenseMap, so that iteration order will be
1365   // the same as insertion order. This is needed to obtain a deterministic
1366   // order of diagnostics when calling flushDiagnostics().
1367   typedef llvm::MapVector<const VarDecl *, MappedType> UsesMap;
1368   UsesMap uses;
1369 
1370 public:
UninitValsDiagReporter(Sema & S)1371   UninitValsDiagReporter(Sema &S) : S(S) {}
~UninitValsDiagReporter()1372   ~UninitValsDiagReporter() override { flushDiagnostics(); }
1373 
getUses(const VarDecl * vd)1374   MappedType &getUses(const VarDecl *vd) {
1375     MappedType &V = uses[vd];
1376     if (!V.getPointer())
1377       V.setPointer(new UsesVec());
1378     return V;
1379   }
1380 
handleUseOfUninitVariable(const VarDecl * vd,const UninitUse & use)1381   void handleUseOfUninitVariable(const VarDecl *vd,
1382                                  const UninitUse &use) override {
1383     getUses(vd).getPointer()->push_back(use);
1384   }
1385 
handleSelfInit(const VarDecl * vd)1386   void handleSelfInit(const VarDecl *vd) override {
1387     getUses(vd).setInt(true);
1388   }
1389 
flushDiagnostics()1390   void flushDiagnostics() {
1391     for (const auto &P : uses) {
1392       const VarDecl *vd = P.first;
1393       const MappedType &V = P.second;
1394 
1395       UsesVec *vec = V.getPointer();
1396       bool hasSelfInit = V.getInt();
1397 
1398       // Specially handle the case where we have uses of an uninitialized
1399       // variable, but the root cause is an idiomatic self-init.  We want
1400       // to report the diagnostic at the self-init since that is the root cause.
1401       if (!vec->empty() && hasSelfInit && hasAlwaysUninitializedUse(vec))
1402         DiagnoseUninitializedUse(S, vd,
1403                                  UninitUse(vd->getInit()->IgnoreParenCasts(),
1404                                            /* isAlwaysUninit */ true),
1405                                  /* alwaysReportSelfInit */ true);
1406       else {
1407         // Sort the uses by their SourceLocations.  While not strictly
1408         // guaranteed to produce them in line/column order, this will provide
1409         // a stable ordering.
1410         std::sort(vec->begin(), vec->end(),
1411                   [](const UninitUse &a, const UninitUse &b) {
1412           // Prefer a more confident report over a less confident one.
1413           if (a.getKind() != b.getKind())
1414             return a.getKind() > b.getKind();
1415           return a.getUser()->getLocStart() < b.getUser()->getLocStart();
1416         });
1417 
1418         for (const auto &U : *vec) {
1419           // If we have self-init, downgrade all uses to 'may be uninitialized'.
1420           UninitUse Use = hasSelfInit ? UninitUse(U.getUser(), false) : U;
1421 
1422           if (DiagnoseUninitializedUse(S, vd, Use))
1423             // Skip further diagnostics for this variable. We try to warn only
1424             // on the first point at which a variable is used uninitialized.
1425             break;
1426         }
1427       }
1428 
1429       // Release the uses vector.
1430       delete vec;
1431     }
1432 
1433     uses.clear();
1434   }
1435 
1436 private:
hasAlwaysUninitializedUse(const UsesVec * vec)1437   static bool hasAlwaysUninitializedUse(const UsesVec* vec) {
1438     return std::any_of(vec->begin(), vec->end(), [](const UninitUse &U) {
1439       return U.getKind() == UninitUse::Always ||
1440              U.getKind() == UninitUse::AfterCall ||
1441              U.getKind() == UninitUse::AfterDecl;
1442     });
1443   }
1444 };
1445 } // anonymous namespace
1446 
1447 namespace clang {
1448 namespace {
1449 typedef SmallVector<PartialDiagnosticAt, 1> OptionalNotes;
1450 typedef std::pair<PartialDiagnosticAt, OptionalNotes> DelayedDiag;
1451 typedef std::list<DelayedDiag> DiagList;
1452 
1453 struct SortDiagBySourceLocation {
1454   SourceManager &SM;
SortDiagBySourceLocationclang::__anon6dec69460d11::SortDiagBySourceLocation1455   SortDiagBySourceLocation(SourceManager &SM) : SM(SM) {}
1456 
operator ()clang::__anon6dec69460d11::SortDiagBySourceLocation1457   bool operator()(const DelayedDiag &left, const DelayedDiag &right) {
1458     // Although this call will be slow, this is only called when outputting
1459     // multiple warnings.
1460     return SM.isBeforeInTranslationUnit(left.first.first, right.first.first);
1461   }
1462 };
1463 } // anonymous namespace
1464 } // namespace clang
1465 
1466 //===----------------------------------------------------------------------===//
1467 // -Wthread-safety
1468 //===----------------------------------------------------------------------===//
1469 namespace clang {
1470 namespace threadSafety {
1471 namespace {
1472 class ThreadSafetyReporter : public clang::threadSafety::ThreadSafetyHandler {
1473   Sema &S;
1474   DiagList Warnings;
1475   SourceLocation FunLocation, FunEndLocation;
1476 
1477   const FunctionDecl *CurrentFunction;
1478   bool Verbose;
1479 
getNotes() const1480   OptionalNotes getNotes() const {
1481     if (Verbose && CurrentFunction) {
1482       PartialDiagnosticAt FNote(CurrentFunction->getBody()->getLocStart(),
1483                                 S.PDiag(diag::note_thread_warning_in_fun)
1484                                     << CurrentFunction->getNameAsString());
1485       return OptionalNotes(1, FNote);
1486     }
1487     return OptionalNotes();
1488   }
1489 
getNotes(const PartialDiagnosticAt & Note) const1490   OptionalNotes getNotes(const PartialDiagnosticAt &Note) const {
1491     OptionalNotes ONS(1, Note);
1492     if (Verbose && CurrentFunction) {
1493       PartialDiagnosticAt FNote(CurrentFunction->getBody()->getLocStart(),
1494                                 S.PDiag(diag::note_thread_warning_in_fun)
1495                                     << CurrentFunction->getNameAsString());
1496       ONS.push_back(std::move(FNote));
1497     }
1498     return ONS;
1499   }
1500 
getNotes(const PartialDiagnosticAt & Note1,const PartialDiagnosticAt & Note2) const1501   OptionalNotes getNotes(const PartialDiagnosticAt &Note1,
1502                          const PartialDiagnosticAt &Note2) const {
1503     OptionalNotes ONS;
1504     ONS.push_back(Note1);
1505     ONS.push_back(Note2);
1506     if (Verbose && CurrentFunction) {
1507       PartialDiagnosticAt FNote(CurrentFunction->getBody()->getLocStart(),
1508                                 S.PDiag(diag::note_thread_warning_in_fun)
1509                                     << CurrentFunction->getNameAsString());
1510       ONS.push_back(std::move(FNote));
1511     }
1512     return ONS;
1513   }
1514 
1515   // Helper functions
warnLockMismatch(unsigned DiagID,StringRef Kind,Name LockName,SourceLocation Loc)1516   void warnLockMismatch(unsigned DiagID, StringRef Kind, Name LockName,
1517                         SourceLocation Loc) {
1518     // Gracefully handle rare cases when the analysis can't get a more
1519     // precise source location.
1520     if (!Loc.isValid())
1521       Loc = FunLocation;
1522     PartialDiagnosticAt Warning(Loc, S.PDiag(DiagID) << Kind << LockName);
1523     Warnings.emplace_back(std::move(Warning), getNotes());
1524   }
1525 
1526  public:
ThreadSafetyReporter(Sema & S,SourceLocation FL,SourceLocation FEL)1527   ThreadSafetyReporter(Sema &S, SourceLocation FL, SourceLocation FEL)
1528     : S(S), FunLocation(FL), FunEndLocation(FEL),
1529       CurrentFunction(nullptr), Verbose(false) {}
1530 
setVerbose(bool b)1531   void setVerbose(bool b) { Verbose = b; }
1532 
1533   /// \brief Emit all buffered diagnostics in order of sourcelocation.
1534   /// We need to output diagnostics produced while iterating through
1535   /// the lockset in deterministic order, so this function orders diagnostics
1536   /// and outputs them.
emitDiagnostics()1537   void emitDiagnostics() {
1538     Warnings.sort(SortDiagBySourceLocation(S.getSourceManager()));
1539     for (const auto &Diag : Warnings) {
1540       S.Diag(Diag.first.first, Diag.first.second);
1541       for (const auto &Note : Diag.second)
1542         S.Diag(Note.first, Note.second);
1543     }
1544   }
1545 
handleInvalidLockExp(StringRef Kind,SourceLocation Loc)1546   void handleInvalidLockExp(StringRef Kind, SourceLocation Loc) override {
1547     PartialDiagnosticAt Warning(Loc, S.PDiag(diag::warn_cannot_resolve_lock)
1548                                          << Loc);
1549     Warnings.emplace_back(std::move(Warning), getNotes());
1550   }
1551 
handleUnmatchedUnlock(StringRef Kind,Name LockName,SourceLocation Loc)1552   void handleUnmatchedUnlock(StringRef Kind, Name LockName,
1553                              SourceLocation Loc) override {
1554     warnLockMismatch(diag::warn_unlock_but_no_lock, Kind, LockName, Loc);
1555   }
1556 
handleIncorrectUnlockKind(StringRef Kind,Name LockName,LockKind Expected,LockKind Received,SourceLocation Loc)1557   void handleIncorrectUnlockKind(StringRef Kind, Name LockName,
1558                                  LockKind Expected, LockKind Received,
1559                                  SourceLocation Loc) override {
1560     if (Loc.isInvalid())
1561       Loc = FunLocation;
1562     PartialDiagnosticAt Warning(Loc, S.PDiag(diag::warn_unlock_kind_mismatch)
1563                                          << Kind << LockName << Received
1564                                          << Expected);
1565     Warnings.emplace_back(std::move(Warning), getNotes());
1566   }
1567 
handleDoubleLock(StringRef Kind,Name LockName,SourceLocation Loc)1568   void handleDoubleLock(StringRef Kind, Name LockName, SourceLocation Loc) override {
1569     warnLockMismatch(diag::warn_double_lock, Kind, LockName, Loc);
1570   }
1571 
handleMutexHeldEndOfScope(StringRef Kind,Name LockName,SourceLocation LocLocked,SourceLocation LocEndOfScope,LockErrorKind LEK)1572   void handleMutexHeldEndOfScope(StringRef Kind, Name LockName,
1573                                  SourceLocation LocLocked,
1574                                  SourceLocation LocEndOfScope,
1575                                  LockErrorKind LEK) override {
1576     unsigned DiagID = 0;
1577     switch (LEK) {
1578       case LEK_LockedSomePredecessors:
1579         DiagID = diag::warn_lock_some_predecessors;
1580         break;
1581       case LEK_LockedSomeLoopIterations:
1582         DiagID = diag::warn_expecting_lock_held_on_loop;
1583         break;
1584       case LEK_LockedAtEndOfFunction:
1585         DiagID = diag::warn_no_unlock;
1586         break;
1587       case LEK_NotLockedAtEndOfFunction:
1588         DiagID = diag::warn_expecting_locked;
1589         break;
1590     }
1591     if (LocEndOfScope.isInvalid())
1592       LocEndOfScope = FunEndLocation;
1593 
1594     PartialDiagnosticAt Warning(LocEndOfScope, S.PDiag(DiagID) << Kind
1595                                                                << LockName);
1596     if (LocLocked.isValid()) {
1597       PartialDiagnosticAt Note(LocLocked, S.PDiag(diag::note_locked_here)
1598                                               << Kind);
1599       Warnings.emplace_back(std::move(Warning), getNotes(Note));
1600       return;
1601     }
1602     Warnings.emplace_back(std::move(Warning), getNotes());
1603   }
1604 
handleExclusiveAndShared(StringRef Kind,Name LockName,SourceLocation Loc1,SourceLocation Loc2)1605   void handleExclusiveAndShared(StringRef Kind, Name LockName,
1606                                 SourceLocation Loc1,
1607                                 SourceLocation Loc2) override {
1608     PartialDiagnosticAt Warning(Loc1,
1609                                 S.PDiag(diag::warn_lock_exclusive_and_shared)
1610                                     << Kind << LockName);
1611     PartialDiagnosticAt Note(Loc2, S.PDiag(diag::note_lock_exclusive_and_shared)
1612                                        << Kind << LockName);
1613     Warnings.emplace_back(std::move(Warning), getNotes(Note));
1614   }
1615 
handleNoMutexHeld(StringRef Kind,const NamedDecl * D,ProtectedOperationKind POK,AccessKind AK,SourceLocation Loc)1616   void handleNoMutexHeld(StringRef Kind, const NamedDecl *D,
1617                          ProtectedOperationKind POK, AccessKind AK,
1618                          SourceLocation Loc) override {
1619     assert((POK == POK_VarAccess || POK == POK_VarDereference) &&
1620            "Only works for variables");
1621     unsigned DiagID = POK == POK_VarAccess?
1622                         diag::warn_variable_requires_any_lock:
1623                         diag::warn_var_deref_requires_any_lock;
1624     PartialDiagnosticAt Warning(Loc, S.PDiag(DiagID)
1625       << D->getNameAsString() << getLockKindFromAccessKind(AK));
1626     Warnings.emplace_back(std::move(Warning), getNotes());
1627   }
1628 
handleMutexNotHeld(StringRef Kind,const NamedDecl * D,ProtectedOperationKind POK,Name LockName,LockKind LK,SourceLocation Loc,Name * PossibleMatch)1629   void handleMutexNotHeld(StringRef Kind, const NamedDecl *D,
1630                           ProtectedOperationKind POK, Name LockName,
1631                           LockKind LK, SourceLocation Loc,
1632                           Name *PossibleMatch) override {
1633     unsigned DiagID = 0;
1634     if (PossibleMatch) {
1635       switch (POK) {
1636         case POK_VarAccess:
1637           DiagID = diag::warn_variable_requires_lock_precise;
1638           break;
1639         case POK_VarDereference:
1640           DiagID = diag::warn_var_deref_requires_lock_precise;
1641           break;
1642         case POK_FunctionCall:
1643           DiagID = diag::warn_fun_requires_lock_precise;
1644           break;
1645         case POK_PassByRef:
1646           DiagID = diag::warn_guarded_pass_by_reference;
1647           break;
1648         case POK_PtPassByRef:
1649           DiagID = diag::warn_pt_guarded_pass_by_reference;
1650           break;
1651       }
1652       PartialDiagnosticAt Warning(Loc, S.PDiag(DiagID) << Kind
1653                                                        << D->getNameAsString()
1654                                                        << LockName << LK);
1655       PartialDiagnosticAt Note(Loc, S.PDiag(diag::note_found_mutex_near_match)
1656                                         << *PossibleMatch);
1657       if (Verbose && POK == POK_VarAccess) {
1658         PartialDiagnosticAt VNote(D->getLocation(),
1659                                  S.PDiag(diag::note_guarded_by_declared_here)
1660                                      << D->getNameAsString());
1661         Warnings.emplace_back(std::move(Warning), getNotes(Note, VNote));
1662       } else
1663         Warnings.emplace_back(std::move(Warning), getNotes(Note));
1664     } else {
1665       switch (POK) {
1666         case POK_VarAccess:
1667           DiagID = diag::warn_variable_requires_lock;
1668           break;
1669         case POK_VarDereference:
1670           DiagID = diag::warn_var_deref_requires_lock;
1671           break;
1672         case POK_FunctionCall:
1673           DiagID = diag::warn_fun_requires_lock;
1674           break;
1675         case POK_PassByRef:
1676           DiagID = diag::warn_guarded_pass_by_reference;
1677           break;
1678         case POK_PtPassByRef:
1679           DiagID = diag::warn_pt_guarded_pass_by_reference;
1680           break;
1681       }
1682       PartialDiagnosticAt Warning(Loc, S.PDiag(DiagID) << Kind
1683                                                        << D->getNameAsString()
1684                                                        << LockName << LK);
1685       if (Verbose && POK == POK_VarAccess) {
1686         PartialDiagnosticAt Note(D->getLocation(),
1687                                  S.PDiag(diag::note_guarded_by_declared_here)
1688                                      << D->getNameAsString());
1689         Warnings.emplace_back(std::move(Warning), getNotes(Note));
1690       } else
1691         Warnings.emplace_back(std::move(Warning), getNotes());
1692     }
1693   }
1694 
handleNegativeNotHeld(StringRef Kind,Name LockName,Name Neg,SourceLocation Loc)1695   void handleNegativeNotHeld(StringRef Kind, Name LockName, Name Neg,
1696                              SourceLocation Loc) override {
1697     PartialDiagnosticAt Warning(Loc,
1698         S.PDiag(diag::warn_acquire_requires_negative_cap)
1699         << Kind << LockName << Neg);
1700     Warnings.emplace_back(std::move(Warning), getNotes());
1701   }
1702 
handleFunExcludesLock(StringRef Kind,Name FunName,Name LockName,SourceLocation Loc)1703   void handleFunExcludesLock(StringRef Kind, Name FunName, Name LockName,
1704                              SourceLocation Loc) override {
1705     PartialDiagnosticAt Warning(Loc, S.PDiag(diag::warn_fun_excludes_mutex)
1706                                          << Kind << FunName << LockName);
1707     Warnings.emplace_back(std::move(Warning), getNotes());
1708   }
1709 
handleLockAcquiredBefore(StringRef Kind,Name L1Name,Name L2Name,SourceLocation Loc)1710   void handleLockAcquiredBefore(StringRef Kind, Name L1Name, Name L2Name,
1711                                 SourceLocation Loc) override {
1712     PartialDiagnosticAt Warning(Loc,
1713       S.PDiag(diag::warn_acquired_before) << Kind << L1Name << L2Name);
1714     Warnings.emplace_back(std::move(Warning), getNotes());
1715   }
1716 
handleBeforeAfterCycle(Name L1Name,SourceLocation Loc)1717   void handleBeforeAfterCycle(Name L1Name, SourceLocation Loc) override {
1718     PartialDiagnosticAt Warning(Loc,
1719       S.PDiag(diag::warn_acquired_before_after_cycle) << L1Name);
1720     Warnings.emplace_back(std::move(Warning), getNotes());
1721   }
1722 
enterFunction(const FunctionDecl * FD)1723   void enterFunction(const FunctionDecl* FD) override {
1724     CurrentFunction = FD;
1725   }
1726 
leaveFunction(const FunctionDecl * FD)1727   void leaveFunction(const FunctionDecl* FD) override {
1728     CurrentFunction = nullptr;
1729   }
1730 };
1731 } // anonymous namespace
1732 } // namespace threadSafety
1733 } // namespace clang
1734 
1735 //===----------------------------------------------------------------------===//
1736 // -Wconsumed
1737 //===----------------------------------------------------------------------===//
1738 
1739 namespace clang {
1740 namespace consumed {
1741 namespace {
1742 class ConsumedWarningsHandler : public ConsumedWarningsHandlerBase {
1743 
1744   Sema &S;
1745   DiagList Warnings;
1746 
1747 public:
1748 
ConsumedWarningsHandler(Sema & S)1749   ConsumedWarningsHandler(Sema &S) : S(S) {}
1750 
emitDiagnostics()1751   void emitDiagnostics() override {
1752     Warnings.sort(SortDiagBySourceLocation(S.getSourceManager()));
1753     for (const auto &Diag : Warnings) {
1754       S.Diag(Diag.first.first, Diag.first.second);
1755       for (const auto &Note : Diag.second)
1756         S.Diag(Note.first, Note.second);
1757     }
1758   }
1759 
warnLoopStateMismatch(SourceLocation Loc,StringRef VariableName)1760   void warnLoopStateMismatch(SourceLocation Loc,
1761                              StringRef VariableName) override {
1762     PartialDiagnosticAt Warning(Loc, S.PDiag(diag::warn_loop_state_mismatch) <<
1763       VariableName);
1764 
1765     Warnings.emplace_back(std::move(Warning), OptionalNotes());
1766   }
1767 
warnParamReturnTypestateMismatch(SourceLocation Loc,StringRef VariableName,StringRef ExpectedState,StringRef ObservedState)1768   void warnParamReturnTypestateMismatch(SourceLocation Loc,
1769                                         StringRef VariableName,
1770                                         StringRef ExpectedState,
1771                                         StringRef ObservedState) override {
1772 
1773     PartialDiagnosticAt Warning(Loc, S.PDiag(
1774       diag::warn_param_return_typestate_mismatch) << VariableName <<
1775         ExpectedState << ObservedState);
1776 
1777     Warnings.emplace_back(std::move(Warning), OptionalNotes());
1778   }
1779 
warnParamTypestateMismatch(SourceLocation Loc,StringRef ExpectedState,StringRef ObservedState)1780   void warnParamTypestateMismatch(SourceLocation Loc, StringRef ExpectedState,
1781                                   StringRef ObservedState) override {
1782 
1783     PartialDiagnosticAt Warning(Loc, S.PDiag(
1784       diag::warn_param_typestate_mismatch) << ExpectedState << ObservedState);
1785 
1786     Warnings.emplace_back(std::move(Warning), OptionalNotes());
1787   }
1788 
warnReturnTypestateForUnconsumableType(SourceLocation Loc,StringRef TypeName)1789   void warnReturnTypestateForUnconsumableType(SourceLocation Loc,
1790                                               StringRef TypeName) override {
1791     PartialDiagnosticAt Warning(Loc, S.PDiag(
1792       diag::warn_return_typestate_for_unconsumable_type) << TypeName);
1793 
1794     Warnings.emplace_back(std::move(Warning), OptionalNotes());
1795   }
1796 
warnReturnTypestateMismatch(SourceLocation Loc,StringRef ExpectedState,StringRef ObservedState)1797   void warnReturnTypestateMismatch(SourceLocation Loc, StringRef ExpectedState,
1798                                    StringRef ObservedState) override {
1799 
1800     PartialDiagnosticAt Warning(Loc, S.PDiag(
1801       diag::warn_return_typestate_mismatch) << ExpectedState << ObservedState);
1802 
1803     Warnings.emplace_back(std::move(Warning), OptionalNotes());
1804   }
1805 
warnUseOfTempInInvalidState(StringRef MethodName,StringRef State,SourceLocation Loc)1806   void warnUseOfTempInInvalidState(StringRef MethodName, StringRef State,
1807                                    SourceLocation Loc) override {
1808 
1809     PartialDiagnosticAt Warning(Loc, S.PDiag(
1810       diag::warn_use_of_temp_in_invalid_state) << MethodName << State);
1811 
1812     Warnings.emplace_back(std::move(Warning), OptionalNotes());
1813   }
1814 
warnUseInInvalidState(StringRef MethodName,StringRef VariableName,StringRef State,SourceLocation Loc)1815   void warnUseInInvalidState(StringRef MethodName, StringRef VariableName,
1816                              StringRef State, SourceLocation Loc) override {
1817 
1818     PartialDiagnosticAt Warning(Loc, S.PDiag(diag::warn_use_in_invalid_state) <<
1819                                 MethodName << VariableName << State);
1820 
1821     Warnings.emplace_back(std::move(Warning), OptionalNotes());
1822   }
1823 };
1824 } // anonymous namespace
1825 } // namespace consumed
1826 } // namespace clang
1827 
1828 //===----------------------------------------------------------------------===//
1829 // AnalysisBasedWarnings - Worker object used by Sema to execute analysis-based
1830 //  warnings on a function, method, or block.
1831 //===----------------------------------------------------------------------===//
1832 
Policy()1833 clang::sema::AnalysisBasedWarnings::Policy::Policy() {
1834   enableCheckFallThrough = 1;
1835   enableCheckUnreachable = 0;
1836   enableThreadSafetyAnalysis = 0;
1837   enableConsumedAnalysis = 0;
1838 }
1839 
isEnabled(DiagnosticsEngine & D,unsigned diag)1840 static unsigned isEnabled(DiagnosticsEngine &D, unsigned diag) {
1841   return (unsigned)!D.isIgnored(diag, SourceLocation());
1842 }
1843 
AnalysisBasedWarnings(Sema & s)1844 clang::sema::AnalysisBasedWarnings::AnalysisBasedWarnings(Sema &s)
1845   : S(s),
1846     NumFunctionsAnalyzed(0),
1847     NumFunctionsWithBadCFGs(0),
1848     NumCFGBlocks(0),
1849     MaxCFGBlocksPerFunction(0),
1850     NumUninitAnalysisFunctions(0),
1851     NumUninitAnalysisVariables(0),
1852     MaxUninitAnalysisVariablesPerFunction(0),
1853     NumUninitAnalysisBlockVisits(0),
1854     MaxUninitAnalysisBlockVisitsPerFunction(0) {
1855 
1856   using namespace diag;
1857   DiagnosticsEngine &D = S.getDiagnostics();
1858 
1859   DefaultPolicy.enableCheckUnreachable =
1860     isEnabled(D, warn_unreachable) ||
1861     isEnabled(D, warn_unreachable_break) ||
1862     isEnabled(D, warn_unreachable_return) ||
1863     isEnabled(D, warn_unreachable_loop_increment);
1864 
1865   DefaultPolicy.enableThreadSafetyAnalysis =
1866     isEnabled(D, warn_double_lock);
1867 
1868   DefaultPolicy.enableConsumedAnalysis =
1869     isEnabled(D, warn_use_in_invalid_state);
1870 }
1871 
flushDiagnostics(Sema & S,const sema::FunctionScopeInfo * fscope)1872 static void flushDiagnostics(Sema &S, const sema::FunctionScopeInfo *fscope) {
1873   for (const auto &D : fscope->PossiblyUnreachableDiags)
1874     S.Diag(D.Loc, D.PD);
1875 }
1876 
1877 void clang::sema::
IssueWarnings(sema::AnalysisBasedWarnings::Policy P,sema::FunctionScopeInfo * fscope,const Decl * D,const BlockExpr * blkExpr)1878 AnalysisBasedWarnings::IssueWarnings(sema::AnalysisBasedWarnings::Policy P,
1879                                      sema::FunctionScopeInfo *fscope,
1880                                      const Decl *D, const BlockExpr *blkExpr) {
1881 
1882   // We avoid doing analysis-based warnings when there are errors for
1883   // two reasons:
1884   // (1) The CFGs often can't be constructed (if the body is invalid), so
1885   //     don't bother trying.
1886   // (2) The code already has problems; running the analysis just takes more
1887   //     time.
1888   DiagnosticsEngine &Diags = S.getDiagnostics();
1889 
1890   // Do not do any analysis for declarations in system headers if we are
1891   // going to just ignore them.
1892   if (Diags.getSuppressSystemWarnings() &&
1893       S.SourceMgr.isInSystemHeader(D->getLocation()))
1894     return;
1895 
1896   // For code in dependent contexts, we'll do this at instantiation time.
1897   if (cast<DeclContext>(D)->isDependentContext())
1898     return;
1899 
1900   if (Diags.hasUncompilableErrorOccurred()) {
1901     // Flush out any possibly unreachable diagnostics.
1902     flushDiagnostics(S, fscope);
1903     return;
1904   }
1905 
1906   const Stmt *Body = D->getBody();
1907   assert(Body);
1908 
1909   // Construct the analysis context with the specified CFG build options.
1910   AnalysisDeclContext AC(/* AnalysisDeclContextManager */ nullptr, D);
1911 
1912   // Don't generate EH edges for CallExprs as we'd like to avoid the n^2
1913   // explosion for destructors that can result and the compile time hit.
1914   AC.getCFGBuildOptions().PruneTriviallyFalseEdges = true;
1915   AC.getCFGBuildOptions().AddEHEdges = false;
1916   AC.getCFGBuildOptions().AddInitializers = true;
1917   AC.getCFGBuildOptions().AddImplicitDtors = true;
1918   AC.getCFGBuildOptions().AddTemporaryDtors = true;
1919   AC.getCFGBuildOptions().AddCXXNewAllocator = false;
1920   AC.getCFGBuildOptions().AddCXXDefaultInitExprInCtors = true;
1921 
1922   // Force that certain expressions appear as CFGElements in the CFG.  This
1923   // is used to speed up various analyses.
1924   // FIXME: This isn't the right factoring.  This is here for initial
1925   // prototyping, but we need a way for analyses to say what expressions they
1926   // expect to always be CFGElements and then fill in the BuildOptions
1927   // appropriately.  This is essentially a layering violation.
1928   if (P.enableCheckUnreachable || P.enableThreadSafetyAnalysis ||
1929       P.enableConsumedAnalysis) {
1930     // Unreachable code analysis and thread safety require a linearized CFG.
1931     AC.getCFGBuildOptions().setAllAlwaysAdd();
1932   }
1933   else {
1934     AC.getCFGBuildOptions()
1935       .setAlwaysAdd(Stmt::BinaryOperatorClass)
1936       .setAlwaysAdd(Stmt::CompoundAssignOperatorClass)
1937       .setAlwaysAdd(Stmt::BlockExprClass)
1938       .setAlwaysAdd(Stmt::CStyleCastExprClass)
1939       .setAlwaysAdd(Stmt::DeclRefExprClass)
1940       .setAlwaysAdd(Stmt::ImplicitCastExprClass)
1941       .setAlwaysAdd(Stmt::UnaryOperatorClass)
1942       .setAlwaysAdd(Stmt::AttributedStmtClass);
1943   }
1944 
1945   // Install the logical handler for -Wtautological-overlap-compare
1946   std::unique_ptr<LogicalErrorHandler> LEH;
1947   if (!Diags.isIgnored(diag::warn_tautological_overlap_comparison,
1948                        D->getLocStart())) {
1949     LEH.reset(new LogicalErrorHandler(S));
1950     AC.getCFGBuildOptions().Observer = LEH.get();
1951   }
1952 
1953   // Emit delayed diagnostics.
1954   if (!fscope->PossiblyUnreachableDiags.empty()) {
1955     bool analyzed = false;
1956 
1957     // Register the expressions with the CFGBuilder.
1958     for (const auto &D : fscope->PossiblyUnreachableDiags) {
1959       if (D.stmt)
1960         AC.registerForcedBlockExpression(D.stmt);
1961     }
1962 
1963     if (AC.getCFG()) {
1964       analyzed = true;
1965       for (const auto &D : fscope->PossiblyUnreachableDiags) {
1966         bool processed = false;
1967         if (D.stmt) {
1968           const CFGBlock *block = AC.getBlockForRegisteredExpression(D.stmt);
1969           CFGReverseBlockReachabilityAnalysis *cra =
1970               AC.getCFGReachablityAnalysis();
1971           // FIXME: We should be able to assert that block is non-null, but
1972           // the CFG analysis can skip potentially-evaluated expressions in
1973           // edge cases; see test/Sema/vla-2.c.
1974           if (block && cra) {
1975             // Can this block be reached from the entrance?
1976             if (cra->isReachable(&AC.getCFG()->getEntry(), block))
1977               S.Diag(D.Loc, D.PD);
1978             processed = true;
1979           }
1980         }
1981         if (!processed) {
1982           // Emit the warning anyway if we cannot map to a basic block.
1983           S.Diag(D.Loc, D.PD);
1984         }
1985       }
1986     }
1987 
1988     if (!analyzed)
1989       flushDiagnostics(S, fscope);
1990   }
1991 
1992   // Warning: check missing 'return'
1993   if (P.enableCheckFallThrough) {
1994     const CheckFallThroughDiagnostics &CD =
1995       (isa<BlockDecl>(D) ? CheckFallThroughDiagnostics::MakeForBlock()
1996        : (isa<CXXMethodDecl>(D) &&
1997           cast<CXXMethodDecl>(D)->getOverloadedOperator() == OO_Call &&
1998           cast<CXXMethodDecl>(D)->getParent()->isLambda())
1999             ? CheckFallThroughDiagnostics::MakeForLambda()
2000             : CheckFallThroughDiagnostics::MakeForFunction(D));
2001     CheckFallThroughForBody(S, D, Body, blkExpr, CD, AC);
2002   }
2003 
2004   // Warning: check for unreachable code
2005   if (P.enableCheckUnreachable) {
2006     // Only check for unreachable code on non-template instantiations.
2007     // Different template instantiations can effectively change the control-flow
2008     // and it is very difficult to prove that a snippet of code in a template
2009     // is unreachable for all instantiations.
2010     bool isTemplateInstantiation = false;
2011     if (const FunctionDecl *Function = dyn_cast<FunctionDecl>(D))
2012       isTemplateInstantiation = Function->isTemplateInstantiation();
2013     if (!isTemplateInstantiation)
2014       CheckUnreachable(S, AC);
2015   }
2016 
2017   // Check for thread safety violations
2018   if (P.enableThreadSafetyAnalysis) {
2019     SourceLocation FL = AC.getDecl()->getLocation();
2020     SourceLocation FEL = AC.getDecl()->getLocEnd();
2021     threadSafety::ThreadSafetyReporter Reporter(S, FL, FEL);
2022     if (!Diags.isIgnored(diag::warn_thread_safety_beta, D->getLocStart()))
2023       Reporter.setIssueBetaWarnings(true);
2024     if (!Diags.isIgnored(diag::warn_thread_safety_verbose, D->getLocStart()))
2025       Reporter.setVerbose(true);
2026 
2027     threadSafety::runThreadSafetyAnalysis(AC, Reporter,
2028                                           &S.ThreadSafetyDeclCache);
2029     Reporter.emitDiagnostics();
2030   }
2031 
2032   // Check for violations of consumed properties.
2033   if (P.enableConsumedAnalysis) {
2034     consumed::ConsumedWarningsHandler WarningHandler(S);
2035     consumed::ConsumedAnalyzer Analyzer(WarningHandler);
2036     Analyzer.run(AC);
2037   }
2038 
2039   if (!Diags.isIgnored(diag::warn_uninit_var, D->getLocStart()) ||
2040       !Diags.isIgnored(diag::warn_sometimes_uninit_var, D->getLocStart()) ||
2041       !Diags.isIgnored(diag::warn_maybe_uninit_var, D->getLocStart())) {
2042     if (CFG *cfg = AC.getCFG()) {
2043       UninitValsDiagReporter reporter(S);
2044       UninitVariablesAnalysisStats stats;
2045       std::memset(&stats, 0, sizeof(UninitVariablesAnalysisStats));
2046       runUninitializedVariablesAnalysis(*cast<DeclContext>(D), *cfg, AC,
2047                                         reporter, stats);
2048 
2049       if (S.CollectStats && stats.NumVariablesAnalyzed > 0) {
2050         ++NumUninitAnalysisFunctions;
2051         NumUninitAnalysisVariables += stats.NumVariablesAnalyzed;
2052         NumUninitAnalysisBlockVisits += stats.NumBlockVisits;
2053         MaxUninitAnalysisVariablesPerFunction =
2054             std::max(MaxUninitAnalysisVariablesPerFunction,
2055                      stats.NumVariablesAnalyzed);
2056         MaxUninitAnalysisBlockVisitsPerFunction =
2057             std::max(MaxUninitAnalysisBlockVisitsPerFunction,
2058                      stats.NumBlockVisits);
2059       }
2060     }
2061   }
2062 
2063   bool FallThroughDiagFull =
2064       !Diags.isIgnored(diag::warn_unannotated_fallthrough, D->getLocStart());
2065   bool FallThroughDiagPerFunction = !Diags.isIgnored(
2066       diag::warn_unannotated_fallthrough_per_function, D->getLocStart());
2067   if (FallThroughDiagFull || FallThroughDiagPerFunction ||
2068       fscope->HasFallthroughStmt) {
2069     DiagnoseSwitchLabelsFallthrough(S, AC, !FallThroughDiagFull);
2070   }
2071 
2072   if (S.getLangOpts().ObjCWeak &&
2073       !Diags.isIgnored(diag::warn_arc_repeated_use_of_weak, D->getLocStart()))
2074     diagnoseRepeatedUseOfWeak(S, fscope, D, AC.getParentMap());
2075 
2076 
2077   // Check for infinite self-recursion in functions
2078   if (!Diags.isIgnored(diag::warn_infinite_recursive_function,
2079                        D->getLocStart())) {
2080     if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
2081       checkRecursiveFunction(S, FD, Body, AC);
2082     }
2083   }
2084 
2085   // If none of the previous checks caused a CFG build, trigger one here
2086   // for -Wtautological-overlap-compare
2087   if (!Diags.isIgnored(diag::warn_tautological_overlap_comparison,
2088                                D->getLocStart())) {
2089     AC.getCFG();
2090   }
2091 
2092   // Collect statistics about the CFG if it was built.
2093   if (S.CollectStats && AC.isCFGBuilt()) {
2094     ++NumFunctionsAnalyzed;
2095     if (CFG *cfg = AC.getCFG()) {
2096       // If we successfully built a CFG for this context, record some more
2097       // detail information about it.
2098       NumCFGBlocks += cfg->getNumBlockIDs();
2099       MaxCFGBlocksPerFunction = std::max(MaxCFGBlocksPerFunction,
2100                                          cfg->getNumBlockIDs());
2101     } else {
2102       ++NumFunctionsWithBadCFGs;
2103     }
2104   }
2105 }
2106 
PrintStats() const2107 void clang::sema::AnalysisBasedWarnings::PrintStats() const {
2108   llvm::errs() << "\n*** Analysis Based Warnings Stats:\n";
2109 
2110   unsigned NumCFGsBuilt = NumFunctionsAnalyzed - NumFunctionsWithBadCFGs;
2111   unsigned AvgCFGBlocksPerFunction =
2112       !NumCFGsBuilt ? 0 : NumCFGBlocks/NumCFGsBuilt;
2113   llvm::errs() << NumFunctionsAnalyzed << " functions analyzed ("
2114                << NumFunctionsWithBadCFGs << " w/o CFGs).\n"
2115                << "  " << NumCFGBlocks << " CFG blocks built.\n"
2116                << "  " << AvgCFGBlocksPerFunction
2117                << " average CFG blocks per function.\n"
2118                << "  " << MaxCFGBlocksPerFunction
2119                << " max CFG blocks per function.\n";
2120 
2121   unsigned AvgUninitVariablesPerFunction = !NumUninitAnalysisFunctions ? 0
2122       : NumUninitAnalysisVariables/NumUninitAnalysisFunctions;
2123   unsigned AvgUninitBlockVisitsPerFunction = !NumUninitAnalysisFunctions ? 0
2124       : NumUninitAnalysisBlockVisits/NumUninitAnalysisFunctions;
2125   llvm::errs() << NumUninitAnalysisFunctions
2126                << " functions analyzed for uninitialiazed variables\n"
2127                << "  " << NumUninitAnalysisVariables << " variables analyzed.\n"
2128                << "  " << AvgUninitVariablesPerFunction
2129                << " average variables per function.\n"
2130                << "  " << MaxUninitAnalysisVariablesPerFunction
2131                << " max variables per function.\n"
2132                << "  " << NumUninitAnalysisBlockVisits << " block visits.\n"
2133                << "  " << AvgUninitBlockVisitsPerFunction
2134                << " average block visits per function.\n"
2135                << "  " << MaxUninitAnalysisBlockVisitsPerFunction
2136                << " max block visits per function.\n";
2137 }
2138