From 0bb4d46b2be5edd58621416de72e995cd6dd7ec4 Mon Sep 17 00:00:00 2001 From: Gauthier Harnisch Date: Sat, 15 Jun 2019 08:32:56 +0000 Subject: [clang] perform semantic checking in constant context Summary: Since the addition of __builtin_is_constant_evaluated the result of an expression can change based on whether it is evaluated in constant context. a lot of semantic checking performs evaluations with out specifying context. which can lead to wrong diagnostics. for example: ``` constexpr int i0 = (long long)__builtin_is_constant_evaluated() * (1ll << 33); //#1 constexpr int i1 = (long long)!__builtin_is_constant_evaluated() * (1ll << 33); //#2 ``` before the patch, #2 was diagnosed incorrectly and #1 wasn't diagnosed. after the patch #1 is diagnosed as it should and #2 isn't. Changes: - add a flag to Sema to passe in constant context mode. - in SemaChecking.cpp calls to Expr::Evaluate* are now done in constant context when they should. - in SemaChecking.cpp diagnostics for UB are not checked for in constant context because an error will be emitted by the constant evaluator. - in SemaChecking.cpp diagnostics for construct that cannot appear in constant context are not checked for in constant context. - in SemaChecking.cpp diagnostics on constant expression are always emitted because constant expression are always evaluated. - semantic checking for initialization of constexpr variables is now done in constant context. - adapt test that were depending on warning changes. - add test. Reviewers: rsmith Reviewed By: rsmith Subscribers: cfe-commits Tags: #clang Differential Revision: https://reviews.llvm.org/D62009 llvm-svn: 363488 --- clang/lib/Sema/Sema.cpp | 1 + 1 file changed, 1 insertion(+) (limited to 'clang/lib/Sema/Sema.cpp') diff --git a/clang/lib/Sema/Sema.cpp b/clang/lib/Sema/Sema.cpp index 077bb0a61ac..d7a05e731ea 100644 --- a/clang/lib/Sema/Sema.cpp +++ b/clang/lib/Sema/Sema.cpp @@ -158,6 +158,7 @@ Sema::Sema(Preprocessor &pp, ASTContext &ctxt, ASTConsumer &consumer, ThreadSafetyDeclCache(nullptr), VarDataSharingAttributesStack(nullptr), CurScope(nullptr), Ident_super(nullptr), Ident___float128(nullptr) { TUScope = nullptr; + isConstantEvaluatedOverride = false; LoadedExternalKnownNamespaces = false; for (unsigned I = 0; I != NSAPI::NumNSNumberLiteralMethods; ++I) -- cgit v1.2.3