| //=- AnalysisBasedWarnings.cpp - Sema warnings based on libAnalysis -*- C++ -*-=// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file defines analysis_warnings::[Policy,Executor]. |
| // Together they are used by Sema to issue warnings based on inexpensive |
| // static analysis algorithms in libAnalysis. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "clang/Sema/Sema.h" |
| #include "clang/Sema/AnalysisBasedWarnings.h" |
| #include "clang/Basic/SourceManager.h" |
| #include "clang/AST/DeclObjC.h" |
| #include "clang/AST/DeclCXX.h" |
| #include "clang/AST/ExprObjC.h" |
| #include "clang/AST/ExprCXX.h" |
| #include "clang/AST/StmtObjC.h" |
| #include "clang/AST/StmtCXX.h" |
| #include "clang/Analysis/AnalysisContext.h" |
| #include "clang/Analysis/CFG.h" |
| #include "clang/Analysis/Analyses/ReachableCode.h" |
| #include "llvm/ADT/BitVector.h" |
| #include "llvm/Support/Casting.h" |
| |
| using namespace clang; |
| |
| //===----------------------------------------------------------------------===// |
| // Unreachable code analysis. |
| //===----------------------------------------------------------------------===// |
| |
| namespace { |
| class UnreachableCodeHandler : public reachable_code::Callback { |
| Sema &S; |
| public: |
| UnreachableCodeHandler(Sema &s) : S(s) {} |
| |
| void HandleUnreachable(SourceLocation L, SourceRange R1, SourceRange R2) { |
| S.Diag(L, diag::warn_unreachable) << R1 << R2; |
| } |
| }; |
| } |
| |
| /// CheckUnreachable - Check for unreachable code. |
| static void CheckUnreachable(Sema &S, AnalysisContext &AC) { |
| UnreachableCodeHandler UC(S); |
| reachable_code::FindUnreachableCode(AC, UC); |
| } |
| |
| //===----------------------------------------------------------------------===// |
| // Check for missing return value. |
| //===----------------------------------------------------------------------===// |
| |
| enum ControlFlowKind { |
| UnknownFallThrough, |
| NeverFallThrough, |
| MaybeFallThrough, |
| AlwaysFallThrough, |
| NeverFallThroughOrReturn |
| }; |
| |
| /// CheckFallThrough - Check that we don't fall off the end of a |
| /// Statement that should return a value. |
| /// |
| /// \returns AlwaysFallThrough iff we always fall off the end of the statement, |
| /// MaybeFallThrough iff we might or might not fall off the end, |
| /// NeverFallThroughOrReturn iff we never fall off the end of the statement or |
| /// return. We assume NeverFallThrough iff we never fall off the end of the |
| /// statement but we may return. We assume that functions not marked noreturn |
| /// will return. |
| static ControlFlowKind CheckFallThrough(AnalysisContext &AC) { |
| CFG *cfg = AC.getCFG(); |
| if (cfg == 0) return UnknownFallThrough; |
| |
| // The CFG leaves in dead things, and we don't want the dead code paths to |
| // confuse us, so we mark all live things first. |
| llvm::BitVector live(cfg->getNumBlockIDs()); |
| unsigned count = reachable_code::ScanReachableFromBlock(cfg->getEntry(), |
| live); |
| |
| bool AddEHEdges = AC.getAddEHEdges(); |
| if (!AddEHEdges && count != cfg->getNumBlockIDs()) |
| // When there are things remaining dead, and we didn't add EH edges |
| // from CallExprs to the catch clauses, we have to go back and |
| // mark them as live. |
| for (CFG::iterator I = cfg->begin(), E = cfg->end(); I != E; ++I) { |
| CFGBlock &b = **I; |
| if (!live[b.getBlockID()]) { |
| if (b.pred_begin() == b.pred_end()) { |
| if (b.getTerminator() && isa<CXXTryStmt>(b.getTerminator())) |
| // When not adding EH edges from calls, catch clauses |
| // can otherwise seem dead. Avoid noting them as dead. |
| count += reachable_code::ScanReachableFromBlock(b, live); |
| continue; |
| } |
| } |
| } |
| |
| // Now we know what is live, we check the live precessors of the exit block |
| // and look for fall through paths, being careful to ignore normal returns, |
| // and exceptional paths. |
| bool HasLiveReturn = false; |
| bool HasFakeEdge = false; |
| bool HasPlainEdge = false; |
| bool HasAbnormalEdge = false; |
| for (CFGBlock::pred_iterator I=cfg->getExit().pred_begin(), |
| E = cfg->getExit().pred_end(); |
| I != E; |
| ++I) { |
| CFGBlock& B = **I; |
| if (!live[B.getBlockID()]) |
| continue; |
| if (B.size() == 0) { |
| if (B.getTerminator() && isa<CXXTryStmt>(B.getTerminator())) { |
| HasAbnormalEdge = true; |
| continue; |
| } |
| |
| // A labeled empty statement, or the entry block... |
| HasPlainEdge = true; |
| continue; |
| } |
| Stmt *S = B[B.size()-1]; |
| if (isa<ReturnStmt>(S)) { |
| HasLiveReturn = true; |
| continue; |
| } |
| if (isa<ObjCAtThrowStmt>(S)) { |
| HasFakeEdge = true; |
| continue; |
| } |
| if (isa<CXXThrowExpr>(S)) { |
| HasFakeEdge = true; |
| continue; |
| } |
| if (const AsmStmt *AS = dyn_cast<AsmStmt>(S)) { |
| if (AS->isMSAsm()) { |
| HasFakeEdge = true; |
| HasLiveReturn = true; |
| continue; |
| } |
| } |
| if (isa<CXXTryStmt>(S)) { |
| HasAbnormalEdge = true; |
| continue; |
| } |
| |
| bool NoReturnEdge = false; |
| if (CallExpr *C = dyn_cast<CallExpr>(S)) { |
| if (std::find(B.succ_begin(), B.succ_end(), &cfg->getExit()) |
| == B.succ_end()) { |
| HasAbnormalEdge = true; |
| continue; |
| } |
| Expr *CEE = C->getCallee()->IgnoreParenCasts(); |
| if (getFunctionExtInfo(CEE->getType()).getNoReturn()) { |
| NoReturnEdge = true; |
| HasFakeEdge = true; |
| } else if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(CEE)) { |
| ValueDecl *VD = DRE->getDecl(); |
| if (VD->hasAttr<NoReturnAttr>()) { |
| NoReturnEdge = true; |
| HasFakeEdge = true; |
| } |
| } |
| } |
| // FIXME: Remove this hack once temporaries and their destructors are |
| // modeled correctly by the CFG. |
| if (CXXExprWithTemporaries *E = dyn_cast<CXXExprWithTemporaries>(S)) { |
| for (unsigned I = 0, N = E->getNumTemporaries(); I != N; ++I) { |
| const FunctionDecl *FD = E->getTemporary(I)->getDestructor(); |
| if (FD->hasAttr<NoReturnAttr>() || |
| FD->getType()->getAs<FunctionType>()->getNoReturnAttr()) { |
| NoReturnEdge = true; |
| HasFakeEdge = true; |
| break; |
| } |
| } |
| } |
| // FIXME: Add noreturn message sends. |
| if (NoReturnEdge == false) |
| HasPlainEdge = true; |
| } |
| if (!HasPlainEdge) { |
| if (HasLiveReturn) |
| return NeverFallThrough; |
| return NeverFallThroughOrReturn; |
| } |
| if (HasAbnormalEdge || HasFakeEdge || HasLiveReturn) |
| return MaybeFallThrough; |
| // This says AlwaysFallThrough for calls to functions that are not marked |
| // noreturn, that don't return. If people would like this warning to be more |
| // accurate, such functions should be marked as noreturn. |
| return AlwaysFallThrough; |
| } |
| |
| namespace { |
| |
| struct CheckFallThroughDiagnostics { |
| unsigned diag_MaybeFallThrough_HasNoReturn; |
| unsigned diag_MaybeFallThrough_ReturnsNonVoid; |
| unsigned diag_AlwaysFallThrough_HasNoReturn; |
| unsigned diag_AlwaysFallThrough_ReturnsNonVoid; |
| unsigned diag_NeverFallThroughOrReturn; |
| bool funMode; |
| |
| static CheckFallThroughDiagnostics MakeForFunction(const Decl *Func) { |
| CheckFallThroughDiagnostics D; |
| D.diag_MaybeFallThrough_HasNoReturn = |
| diag::warn_falloff_noreturn_function; |
| D.diag_MaybeFallThrough_ReturnsNonVoid = |
| diag::warn_maybe_falloff_nonvoid_function; |
| D.diag_AlwaysFallThrough_HasNoReturn = |
| diag::warn_falloff_noreturn_function; |
| D.diag_AlwaysFallThrough_ReturnsNonVoid = |
| diag::warn_falloff_nonvoid_function; |
| |
| // Don't suggest that virtual functions be marked "noreturn", since they |
| // might be overridden by non-noreturn functions. |
| bool isVirtualMethod = false; |
| if (const CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(Func)) |
| isVirtualMethod = Method->isVirtual(); |
| |
| if (!isVirtualMethod) |
| D.diag_NeverFallThroughOrReturn = |
| diag::warn_suggest_noreturn_function; |
| else |
| D.diag_NeverFallThroughOrReturn = 0; |
| |
| D.funMode = true; |
| return D; |
| } |
| |
| static CheckFallThroughDiagnostics MakeForBlock() { |
| CheckFallThroughDiagnostics D; |
| D.diag_MaybeFallThrough_HasNoReturn = |
| diag::err_noreturn_block_has_return_expr; |
| D.diag_MaybeFallThrough_ReturnsNonVoid = |
| diag::err_maybe_falloff_nonvoid_block; |
| D.diag_AlwaysFallThrough_HasNoReturn = |
| diag::err_noreturn_block_has_return_expr; |
| D.diag_AlwaysFallThrough_ReturnsNonVoid = |
| diag::err_falloff_nonvoid_block; |
| D.diag_NeverFallThroughOrReturn = |
| diag::warn_suggest_noreturn_block; |
| D.funMode = false; |
| return D; |
| } |
| |
| bool checkDiagnostics(Diagnostic &D, bool ReturnsVoid, |
| bool HasNoReturn) const { |
| if (funMode) { |
| return (D.getDiagnosticLevel(diag::warn_maybe_falloff_nonvoid_function) |
| == Diagnostic::Ignored || ReturnsVoid) |
| && (D.getDiagnosticLevel(diag::warn_noreturn_function_has_return_expr) |
| == Diagnostic::Ignored || !HasNoReturn) |
| && (D.getDiagnosticLevel(diag::warn_suggest_noreturn_block) |
| == Diagnostic::Ignored || !ReturnsVoid); |
| } |
| |
| // For blocks. |
| return ReturnsVoid && !HasNoReturn |
| && (D.getDiagnosticLevel(diag::warn_suggest_noreturn_block) |
| == Diagnostic::Ignored || !ReturnsVoid); |
| } |
| }; |
| |
| } |
| |
| /// CheckFallThroughForFunctionDef - Check that we don't fall off the end of a |
| /// function that should return a value. Check that we don't fall off the end |
| /// of a noreturn function. We assume that functions and blocks not marked |
| /// noreturn will return. |
| static void CheckFallThroughForBody(Sema &S, const Decl *D, const Stmt *Body, |
| QualType BlockTy, |
| const CheckFallThroughDiagnostics& CD, |
| AnalysisContext &AC) { |
| |
| bool ReturnsVoid = false; |
| bool HasNoReturn = false; |
| |
| if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) { |
| ReturnsVoid = FD->getResultType()->isVoidType(); |
| HasNoReturn = FD->hasAttr<NoReturnAttr>() || |
| FD->getType()->getAs<FunctionType>()->getNoReturnAttr(); |
| } |
| else if (const ObjCMethodDecl *MD = dyn_cast<ObjCMethodDecl>(D)) { |
| ReturnsVoid = MD->getResultType()->isVoidType(); |
| HasNoReturn = MD->hasAttr<NoReturnAttr>(); |
| } |
| else if (isa<BlockDecl>(D)) { |
| if (const FunctionType *FT = |
| BlockTy->getPointeeType()->getAs<FunctionType>()) { |
| if (FT->getResultType()->isVoidType()) |
| ReturnsVoid = true; |
| if (FT->getNoReturnAttr()) |
| HasNoReturn = true; |
| } |
| } |
| |
| Diagnostic &Diags = S.getDiagnostics(); |
| |
| // Short circuit for compilation speed. |
| if (CD.checkDiagnostics(Diags, ReturnsVoid, HasNoReturn)) |
| return; |
| |
| // FIXME: Function try block |
| if (const CompoundStmt *Compound = dyn_cast<CompoundStmt>(Body)) { |
| switch (CheckFallThrough(AC)) { |
| case UnknownFallThrough: |
| break; |
| |
| case MaybeFallThrough: |
| if (HasNoReturn) |
| S.Diag(Compound->getRBracLoc(), |
| CD.diag_MaybeFallThrough_HasNoReturn); |
| else if (!ReturnsVoid) |
| S.Diag(Compound->getRBracLoc(), |
| CD.diag_MaybeFallThrough_ReturnsNonVoid); |
| break; |
| case AlwaysFallThrough: |
| if (HasNoReturn) |
| S.Diag(Compound->getRBracLoc(), |
| CD.diag_AlwaysFallThrough_HasNoReturn); |
| else if (!ReturnsVoid) |
| S.Diag(Compound->getRBracLoc(), |
| CD.diag_AlwaysFallThrough_ReturnsNonVoid); |
| break; |
| case NeverFallThroughOrReturn: |
| if (ReturnsVoid && !HasNoReturn && CD.diag_NeverFallThroughOrReturn) |
| S.Diag(Compound->getLBracLoc(), |
| CD.diag_NeverFallThroughOrReturn); |
| break; |
| case NeverFallThrough: |
| break; |
| } |
| } |
| } |
| |
| //===----------------------------------------------------------------------===// |
| // AnalysisBasedWarnings - Worker object used by Sema to execute analysis-based |
| // warnings on a function, method, or block. |
| //===----------------------------------------------------------------------===// |
| |
| clang::sema::AnalysisBasedWarnings::Policy::Policy() { |
| enableCheckFallThrough = 1; |
| enableCheckUnreachable = 0; |
| } |
| |
| clang::sema::AnalysisBasedWarnings::AnalysisBasedWarnings(Sema &s) : S(s) { |
| Diagnostic &D = S.getDiagnostics(); |
| DefaultPolicy.enableCheckUnreachable = (unsigned) |
| (D.getDiagnosticLevel(diag::warn_unreachable) != Diagnostic::Ignored); |
| } |
| |
| void clang::sema:: |
| AnalysisBasedWarnings::IssueWarnings(sema::AnalysisBasedWarnings::Policy P, |
| const Decl *D, QualType BlockTy) { |
| |
| assert(BlockTy.isNull() || isa<BlockDecl>(D)); |
| |
| // We avoid doing analysis-based warnings when there are errors for |
| // two reasons: |
| // (1) The CFGs often can't be constructed (if the body is invalid), so |
| // don't bother trying. |
| // (2) The code already has problems; running the analysis just takes more |
| // time. |
| Diagnostic &Diags = S.getDiagnostics(); |
| |
| if (Diags.hasErrorOccurred() || Diags.hasFatalErrorOccurred()) |
| return; |
| |
| // Do not do any analysis for declarations in system headers if we are |
| // going to just ignore them. |
| if (Diags.getSuppressSystemWarnings() && |
| S.SourceMgr.isInSystemHeader(D->getLocation())) |
| return; |
| |
| // For code in dependent contexts, we'll do this at instantiation time. |
| if (cast<DeclContext>(D)->isDependentContext()) |
| return; |
| |
| const Stmt *Body = D->getBody(); |
| assert(Body); |
| |
| // Don't generate EH edges for CallExprs as we'd like to avoid the n^2 |
| // explosion for destrutors that can result and the compile time hit. |
| AnalysisContext AC(D, 0, false); |
| |
| // Warning: check missing 'return' |
| if (P.enableCheckFallThrough) { |
| const CheckFallThroughDiagnostics &CD = |
| (isa<BlockDecl>(D) ? CheckFallThroughDiagnostics::MakeForBlock() |
| : CheckFallThroughDiagnostics::MakeForFunction(D)); |
| CheckFallThroughForBody(S, D, Body, BlockTy, CD, AC); |
| } |
| |
| // Warning: check for unreachable code |
| if (P.enableCheckUnreachable) |
| CheckUnreachable(S, AC); |
| } |
| |
| void clang::sema:: |
| AnalysisBasedWarnings::IssueWarnings(sema::AnalysisBasedWarnings::Policy P, |
| const BlockExpr *E) { |
| return IssueWarnings(P, E->getBlockDecl(), E->getType()); |
| } |
| |
| void clang::sema:: |
| AnalysisBasedWarnings::IssueWarnings(sema::AnalysisBasedWarnings::Policy P, |
| const ObjCMethodDecl *D) { |
| return IssueWarnings(P, D, QualType()); |
| } |
| |
| void clang::sema:: |
| AnalysisBasedWarnings::IssueWarnings(sema::AnalysisBasedWarnings::Policy P, |
| const FunctionDecl *D) { |
| return IssueWarnings(P, D, QualType()); |
| } |