https://github.com/efriedma-quic created
https://github.com/llvm/llvm-project/pull/142498
If we see a parameter of reference type that isn't part of the frame, don't try
to evaluate its default argument. Just treat it as a constexpr-unknown value.
Fixes #141114. Fixes #141858.
>From 08d64f594d60c8f488c1dfab70b7f8a5b8ae4157 Mon Sep 17 00:00:00 2001
From: Eli Friedman <efrie...@quicinc.com>
Date: Mon, 2 Jun 2025 15:44:35 -0700
Subject: [PATCH] [clang] Don't evaluate the initializer of constexpr-unknown
parameters.
If we see a parameter of reference type that isn't part of the frame,
don't try to evaluate its defualt argument. Just treat it as a
constexpr-unknown value.
Fixes #141114. Fixes #141858.
---
clang/lib/AST/ExprConstant.cpp | 7 ++++++-
clang/test/SemaCXX/constant-expression-p2280r4.cpp | 12 ++++++++++++
2 files changed, 18 insertions(+), 1 deletion(-)
diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index b20e2690d0eee..ab964e592de80 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -3550,7 +3550,12 @@ static bool evaluateVarDeclInit(EvalInfo &Info, const
Expr *E,
// should begin within the evaluation of E
// Used to be C++20 [expr.const]p5.12.2:
// ... its lifetime began within the evaluation of E;
- if (isa<ParmVarDecl>(VD) && !AllowConstexprUnknown) {
+ if (isa<ParmVarDecl>(VD)) {
+ if (AllowConstexprUnknown) {
+ Result = &Info.CurrentCall->createConstexprUnknownAPValues(VD, Base);
+ return true;
+ }
+
// Assume parameters of a potential constant expression are usable in
// constant expressions.
if (!Info.checkingPotentialConstantExpression() ||
diff --git a/clang/test/SemaCXX/constant-expression-p2280r4.cpp
b/clang/test/SemaCXX/constant-expression-p2280r4.cpp
index c14250a268f6c..50637917ba210 100644
--- a/clang/test/SemaCXX/constant-expression-p2280r4.cpp
+++ b/clang/test/SemaCXX/constant-expression-p2280r4.cpp
@@ -250,3 +250,15 @@ namespace uninit_reference_used {
// expected-note {{in call to 'g5()'}}
}
+
+namespace param_reference {
+ constexpr int arbitrary = -12345;
+ constexpr void f(const int &x = arbitrary) { // expected-note {{declared
here}}
+ constexpr const int &v1 = x; // expected-error {{must be initialized by a
constant expression}} \
+ // expected-note {{reference to 'x' is not a constant expression}}
+ constexpr const int &v2 = (x, arbitrary); // expected-warning {{left
operand of comma operator has no effect}}
+ constexpr int v3 = x; // expected-error {{must be initialized by a
constant expression}}
+ static_assert(x==arbitrary); // expected-error {{static assertion
expression is not an integral constant expression}}
+ static_assert(&x - &x == 0);
+ }
+}
_______________________________________________
cfe-commits mailing list
cfe-commits@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
