Author: rsmith Date: Tue Mar 21 20:49:19 2017 New Revision: 298477 URL: http://llvm.org/viewvc/llvm-project?rev=298477&view=rev Log: Suppress warning on unreachable [[clang::fallthrough]] within a template instantiation.
We don't know whether some other instantiation of the template might be able to reach the annotation, so warning on it has a high chance of false positives. Patch by Ahmed Asadi! Differential Revision: https://reviews.llvm.org/D31069 Added: cfe/trunk/test/SemaCXX/P30636.cpp Modified: cfe/trunk/lib/Sema/AnalysisBasedWarnings.cpp Modified: cfe/trunk/lib/Sema/AnalysisBasedWarnings.cpp URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/AnalysisBasedWarnings.cpp?rev=298477&r1=298476&r2=298477&view=diff ============================================================================== --- cfe/trunk/lib/Sema/AnalysisBasedWarnings.cpp (original) +++ cfe/trunk/lib/Sema/AnalysisBasedWarnings.cpp Tue Mar 21 20:49:19 2017 @@ -972,7 +972,8 @@ namespace { } } - bool checkFallThroughIntoBlock(const CFGBlock &B, int &AnnotatedCnt) { + bool checkFallThroughIntoBlock(const CFGBlock &B, int &AnnotatedCnt, + bool IsTemplateInstantiation) { assert(!ReachableBlocks.empty() && "ReachableBlocks empty"); int UnannotatedCnt = 0; @@ -1002,8 +1003,12 @@ namespace { ElemIt != ElemEnd; ++ElemIt) { if (Optional<CFGStmt> CS = ElemIt->getAs<CFGStmt>()) { if (const AttributedStmt *AS = asFallThroughAttr(CS->getStmt())) { - S.Diag(AS->getLocStart(), - diag::warn_fallthrough_attr_unreachable); + // Don't issue a warning for an unreachable fallthrough + // attribute in template instantiations as it may not be + // unreachable in all instantiations of the template. + if (!IsTemplateInstantiation) + S.Diag(AS->getLocStart(), + diag::warn_fallthrough_attr_unreachable); markFallthroughVisited(AS); ++AnnotatedCnt; break; @@ -1164,7 +1169,11 @@ static void DiagnoseSwitchLabelsFallthro int AnnotatedCnt; - if (!FM.checkFallThroughIntoBlock(*B, AnnotatedCnt)) + bool IsTemplateInstantiation = false; + if (const FunctionDecl *Function = dyn_cast<FunctionDecl>(AC.getDecl())) + IsTemplateInstantiation = Function->isTemplateInstantiation(); + if (!FM.checkFallThroughIntoBlock(*B, AnnotatedCnt, + IsTemplateInstantiation)) continue; S.Diag(Label->getLocStart(), Added: cfe/trunk/test/SemaCXX/P30636.cpp URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/P30636.cpp?rev=298477&view=auto ============================================================================== --- cfe/trunk/test/SemaCXX/P30636.cpp (added) +++ cfe/trunk/test/SemaCXX/P30636.cpp Tue Mar 21 20:49:19 2017 @@ -0,0 +1,20 @@ +// RUN: %clang_cc1 -fsyntax-only -verify -std=c++11 -Wimplicit-fallthrough %s +// expected-no-diagnostics + +template<bool param> +int fallthrough_template(int i) +{ + switch (i) { + case 1: + if (param) + return 3; + [[clang::fallthrough]]; // no warning here, for an unreachable annotation (in the fallthrough_template<true> case) in a template function + case 2: + return 4; + default: + return 5; + } +} + +template int fallthrough_template<true>(int); + _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
