https://github.com/efriedma-quic created
https://github.com/llvm/llvm-project/pull/142885
As discussed in #142707, in the context of determining whether a conversion is
a narrowing conversion, is_constant_evaluation should be false, even it's a
subexpression of a manifestly constant-evaluated expression.
>From e31334671d9f4a5cdddf0de14eced702675dbde2 Mon Sep 17 00:00:00 2001
From: Eli Friedman <efrie...@quicinc.com>
Date: Wed, 4 Jun 2025 18:33:31 -0700
Subject: [PATCH] [clang] Add regression tests for narrowing with
is_constant_evaluated.
As discussed in #142707, in the context of determining whether a
conversion is a narrowing conversion, is_constant_evaluation should be
false, even it's a subexpression of a manifestly constant-evaluated
expression.
---
clang/test/SemaCXX/builtin-is-constant-evaluated.cpp | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/clang/test/SemaCXX/builtin-is-constant-evaluated.cpp
b/clang/test/SemaCXX/builtin-is-constant-evaluated.cpp
index a1c003c85f732..c775fe71069df 100644
--- a/clang/test/SemaCXX/builtin-is-constant-evaluated.cpp
+++ b/clang/test/SemaCXX/builtin-is-constant-evaluated.cpp
@@ -143,3 +143,14 @@ namespace fold_initializer {
const float A::f = __builtin_is_constant_evaluated();
static_assert(fold(A::f == 1.0f));
}
+
+namespace narrowing {
+ struct X { unsigned u; };
+ constexpr int f(X x) {return x.u;}
+ void g() {
+ static_assert(f({0xFFFFFFFFLL + __builtin_is_constant_evaluated()}) == 0);
+ f({0x100000000LL - __builtin_is_constant_evaluated()}); // expected-error
{{constant expression evaluates to 4294967296}} \
+ // expected-warning {{implicit conversion}} \
+ // expected-note {{insert an explicit cast to silence this issue}}
+ }
+}
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