Author: ericwf Date: Fri Mar 8 14:06:48 2019 New Revision: 355743 URL: http://llvm.org/viewvc/llvm-project?rev=355743&view=rev Log: [8.0 Regression] Fix handling of `__builtin_constant_p` inside template arguments, enumerators, case statements, and the enable_if attribute.
Summary: The following code is accepted by Clang 7 and prior but rejected by the upcoming 8 release and in trunk [1] ``` // error {{never produces a constant expression}} void foo(const char* s) __attribute__((enable_if(__builtin_constant_p(*s) == false, "trap"))) {} void test() { foo("abc"); } ``` Prior to Clang 8, the call to `__builtin_constant_p` was a constant expression returning false. Currently, it's not a valid constant expression. The bug is caused because we failed to set `InConstantContext` when attempting to evaluate unevaluated constant expressions. [1] https://godbolt.org/z/ksAjmq Reviewers: rsmith, hans, sbenza Reviewed By: rsmith Subscribers: kristina, cfe-commits Tags: #clang Differential Revision: https://reviews.llvm.org/D59038 Modified: cfe/trunk/lib/AST/ExprConstant.cpp cfe/trunk/test/SemaCXX/constant-expression-cxx1y.cpp cfe/trunk/test/SemaCXX/enable_if.cpp Modified: cfe/trunk/lib/AST/ExprConstant.cpp URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/ExprConstant.cpp?rev=355743&r1=355742&r2=355743&view=diff ============================================================================== --- cfe/trunk/lib/AST/ExprConstant.cpp (original) +++ cfe/trunk/lib/AST/ExprConstant.cpp Fri Mar 8 14:06:48 2019 @@ -11131,6 +11131,7 @@ bool Expr::EvaluateAsConstantExpr(EvalRe const ASTContext &Ctx) const { EvalInfo::EvaluationMode EM = EvalInfo::EM_ConstantExpression; EvalInfo Info(Ctx, Result, EM); + Info.InConstantContext = true; if (!::Evaluate(Result.Val, Info, this)) return false; @@ -11771,6 +11772,7 @@ bool Expr::EvaluateWithSubstitution(APVa const Expr *This) const { Expr::EvalStatus Status; EvalInfo Info(Ctx, Status, EvalInfo::EM_ConstantExpressionUnevaluated); + Info.InConstantContext = true; LValue ThisVal; const LValue *ThisPtr = nullptr; @@ -11854,6 +11856,7 @@ bool Expr::isPotentialConstantExprUneval EvalInfo Info(FD->getASTContext(), Status, EvalInfo::EM_PotentialConstantExpressionUnevaluated); + Info.InConstantContext = true; // Fabricate a call stack frame to give the arguments a plausible cover story. ArrayRef<const Expr*> Args; Modified: cfe/trunk/test/SemaCXX/constant-expression-cxx1y.cpp URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/constant-expression-cxx1y.cpp?rev=355743&r1=355742&r2=355743&view=diff ============================================================================== --- cfe/trunk/test/SemaCXX/constant-expression-cxx1y.cpp (original) +++ cfe/trunk/test/SemaCXX/constant-expression-cxx1y.cpp Fri Mar 8 14:06:48 2019 @@ -1135,3 +1135,27 @@ constexpr bool indirect_builtin_constant return __builtin_constant_p(*__s); } constexpr bool n = indirect_builtin_constant_p("a"); + +__attribute__((enable_if(indirect_builtin_constant_p("a") == n, "OK"))) +int test_in_enable_if() { return 0; } +int n2 = test_in_enable_if(); + +template <bool n = indirect_builtin_constant_p("a")> +int test_in_template_param() { return 0; } +int n3 = test_in_template_param(); + +void test_in_case(int n) { + switch (n) { + case indirect_builtin_constant_p("abc"): + break; + } +} +enum InEnum1 { + ONE = indirect_builtin_constant_p("abc") +}; +enum InEnum2 : int { + TWO = indirect_builtin_constant_p("abc") +}; +enum class InEnum3 { + THREE = indirect_builtin_constant_p("abc") +}; Modified: cfe/trunk/test/SemaCXX/enable_if.cpp URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/enable_if.cpp?rev=355743&r1=355742&r2=355743&view=diff ============================================================================== --- cfe/trunk/test/SemaCXX/enable_if.cpp (original) +++ cfe/trunk/test/SemaCXX/enable_if.cpp Fri Mar 8 14:06:48 2019 @@ -514,3 +514,11 @@ namespace TypeOfFn { static_assert(is_same<__typeof__(foo)*, decltype(&foo)>::value, ""); } + +namespace InConstantContext { +void foo(const char *s) __attribute__((enable_if(((void)__builtin_constant_p(*s), true), "trap"))) {} + +void test() { + InConstantContext::foo("abc"); +} +} // namespace InConstantContext _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits