Author: rsmith
Date: Thu May 2 16:21:28 2019
New Revision: 359844
URL: http://llvm.org/viewvc/llvm-project?rev=359844&view=rev
Log:
Fix -Wunsequenced false-positives in code controlled by a branch on
__builtin_constant_p.
If the operand of __builtin_constant_p is not constant and has
side-effects, then code controlled by a branch on it is unreachable and
we should not emit runtime behavior warnings in such code.
Modified:
cfe/trunk/lib/AST/ExprConstant.cpp
cfe/trunk/test/Sema/warn-unsequenced.c
Modified: cfe/trunk/lib/AST/ExprConstant.cpp
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/ExprConstant.cpp?rev=359844&r1=359843&r2=359844&view=diff
==============================================================================
--- cfe/trunk/lib/AST/ExprConstant.cpp (original)
+++ cfe/trunk/lib/AST/ExprConstant.cpp Thu May 2 16:21:28 2019
@@ -8269,11 +8269,14 @@ bool IntExprEvaluator::VisitBuiltinCallE
case Builtin::BI__builtin_constant_p: {
const Expr *Arg = E->getArg(0);
- if (EvaluateBuiltinConstantP(Info, Arg))
+ if (EvaluateBuiltinConstantP(Info, Arg)) {
return Success(true, E);
- else if (Info.InConstantContext)
+ } else if (Info.InConstantContext || Arg->HasSideEffects(Info.Ctx)) {
+ // Outside a constant context, eagerly evaluate to false in the presence
+ // of side-effects in order to avoid -Wunsequenced false-positives in
+ // a branch on __builtin_constant_p(expr).
return Success(false, E);
- else {
+ } else {
Info.FFDiag(E, diag::note_invalid_subexpr_in_const_expr);
return false;
}
Modified: cfe/trunk/test/Sema/warn-unsequenced.c
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/warn-unsequenced.c?rev=359844&r1=359843&r2=359844&view=diff
==============================================================================
--- cfe/trunk/test/Sema/warn-unsequenced.c (original)
+++ cfe/trunk/test/Sema/warn-unsequenced.c Thu May 2 16:21:28 2019
@@ -93,4 +93,6 @@ void test() {
_Generic(++a, default: 0) + ++a; // ok
sizeof(++a) + ++a; // ok
_Alignof(++a) + ++a; // expected-warning {{extension}}
+
+ __builtin_constant_p(f(++a, 0)) ? f(f(++a, 0), f(++a, 0)) : 0;
}
_______________________________________________
cfe-commits mailing list
cfe-commits@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
