https://github.com/efriedma-quic updated
https://github.com/llvm/llvm-project/pull/149227
>From 9ce04c82fdeb47e337ba47655fd8f626b57313c2 Mon Sep 17 00:00:00 2001
From: Eli Friedman <efrie...@quicinc.com>
Date: Wed, 16 Jul 2025 16:58:03 -0700
Subject: [PATCH 1/2] [clang] Fix potential constant expression checking with
constexpr-unknown.
071765749a70b22fb62f2efc07a3f242ff5b4c52 improved constexpr-unkown
diagnostics, but potential constant expression checking broke in the
process: we produce diagnostics in more cases. Supress the diagnostics
as appropriate.
This fix affects -Winvalid-constexpr and the enable_if attribute. (The
-Winvalid-constexpr diagnostic isn't really important right now, but it
will become important if we allow constexpr-unknown with pre-C++23
standards.)
Fixes #149041. Fixes #149188.
---
clang/lib/AST/ExprConstant.cpp | 11 +++++----
.../SemaCXX/constant-expression-p2280r4.cpp | 24 +++++++++++++++++++
.../test/SemaCXX/constexpr-never-constant.cpp | 5 ++++
3 files changed, 36 insertions(+), 4 deletions(-)
diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index 767cc4c3b19eb..8797eaddd0e18 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -4450,7 +4450,8 @@ static CompleteObject findCompleteObject(EvalInfo &Info,
const Expr *E,
}
} else if (!IsAccess) {
return CompleteObject(LVal.getLValueBase(), nullptr, BaseType);
- } else if (IsConstant && Info.checkingPotentialConstantExpression() &&
+ } else if ((IsConstant || BaseType->isReferenceType()) &&
+ Info.checkingPotentialConstantExpression() &&
BaseType->isLiteralType(Info.Ctx) && !VD->hasDefinition()) {
// This variable might end up being constexpr. Don't diagnose it yet.
} else if (IsConstant) {
@@ -4491,9 +4492,11 @@ static CompleteObject findCompleteObject(EvalInfo &Info,
const Expr *E,
// a null BaseVal. Any constexpr-unknown variable seen here is an error:
// we can't access a constexpr-unknown object.
if (AK != clang::AK_Dereference && !BaseVal) {
- Info.FFDiag(E, diag::note_constexpr_access_unknown_variable, 1)
- << AK << VD;
- Info.Note(VD->getLocation(), diag::note_declared_at);
+ if (!Info.checkingPotentialConstantExpression()) {
+ Info.FFDiag(E, diag::note_constexpr_access_unknown_variable, 1)
+ << AK << VD;
+ Info.Note(VD->getLocation(), diag::note_declared_at);
+ }
return CompleteObject();
}
} else if (DynamicAllocLValue DA = LVal.Base.dyn_cast<DynamicAllocLValue>())
{
diff --git a/clang/test/SemaCXX/constant-expression-p2280r4.cpp
b/clang/test/SemaCXX/constant-expression-p2280r4.cpp
index 03fea91169787..979d29476c119 100644
--- a/clang/test/SemaCXX/constant-expression-p2280r4.cpp
+++ b/clang/test/SemaCXX/constant-expression-p2280r4.cpp
@@ -357,3 +357,27 @@ namespace pointer_comparisons {
static_assert(!f4()); // expected-error {{static assertion expression is not
an integral constant expression}} \
// expected-note {{in call to 'f4()'}}
}
+
+namespace enable_if_1 {
+ template <__SIZE_TYPE__ N>
+ constexpr void foo(const char (&Str)[N])
+ __attribute((enable_if(__builtin_strlen(Str), ""))) {}
+
+ void x() {
+ foo("1234");
+ }
+}
+
+namespace enable_if_2 {
+ constexpr const char (&f())[];
+ extern const char (&Str)[];
+ constexpr int foo()
+ __attribute((enable_if(__builtin_strlen(Str), "")))
+ {return __builtin_strlen(Str);}
+
+ constexpr const char (&f())[] {return "a";}
+ constexpr const char (&Str)[] = f();
+ void x() {
+ constexpr int x = foo();
+ }
+}
diff --git a/clang/test/SemaCXX/constexpr-never-constant.cpp
b/clang/test/SemaCXX/constexpr-never-constant.cpp
index 307810ee263dd..ca6dff22275d5 100644
--- a/clang/test/SemaCXX/constexpr-never-constant.cpp
+++ b/clang/test/SemaCXX/constexpr-never-constant.cpp
@@ -24,3 +24,8 @@ constexpr void other_func() {
throw 12;
}
+
+// Make sure these don't trigger the diagnostic.
+extern const bool& b;
+constexpr bool fun1() { return b; }
+constexpr bool fun2(const bool& b) { return b; }
>From 05e1a7d4e97c7bfc1ac00f0fdeaa0ef78473c2ae Mon Sep 17 00:00:00 2001
From: Eli Friedman <efrie...@quicinc.com>
Date: Thu, 17 Jul 2025 11:47:51 -0700
Subject: [PATCH 2/2] Note bug numbers in tests.
---
clang/test/SemaCXX/constant-expression-p2280r4.cpp | 2 ++
clang/test/SemaCXX/constexpr-never-constant.cpp | 10 ++++++----
2 files changed, 8 insertions(+), 4 deletions(-)
diff --git a/clang/test/SemaCXX/constant-expression-p2280r4.cpp
b/clang/test/SemaCXX/constant-expression-p2280r4.cpp
index 979d29476c119..16f5f823d26c1 100644
--- a/clang/test/SemaCXX/constant-expression-p2280r4.cpp
+++ b/clang/test/SemaCXX/constant-expression-p2280r4.cpp
@@ -358,6 +358,7 @@ namespace pointer_comparisons {
// expected-note {{in call to 'f4()'}}
}
+namespace GH149188 {
namespace enable_if_1 {
template <__SIZE_TYPE__ N>
constexpr void foo(const char (&Str)[N])
@@ -381,3 +382,4 @@ namespace enable_if_2 {
constexpr int x = foo();
}
}
+}
diff --git a/clang/test/SemaCXX/constexpr-never-constant.cpp
b/clang/test/SemaCXX/constexpr-never-constant.cpp
index ca6dff22275d5..5756bb647ce88 100644
--- a/clang/test/SemaCXX/constexpr-never-constant.cpp
+++ b/clang/test/SemaCXX/constexpr-never-constant.cpp
@@ -25,7 +25,9 @@ constexpr void other_func() {
throw 12;
}
-// Make sure these don't trigger the diagnostic.
-extern const bool& b;
-constexpr bool fun1() { return b; }
-constexpr bool fun2(const bool& b) { return b; }
+namespace GH149041 {
+ // Make sure these don't trigger the diagnostic.
+ extern const bool& b;
+ constexpr bool fun1() { return b; }
+ constexpr bool fun2(const bool& b) { return b; }
+}
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