https://github.com/DKLoehr updated
https://github.com/llvm/llvm-project/pull/127843
>From 7a919e29b221f1070c420e263760b7071dc01da8 Mon Sep 17 00:00:00 2001
From: Devon Loehr <dlo...@google.com>
Date: Thu, 20 Feb 2025 15:19:13 +0000
Subject: [PATCH 1/3] Implement mutable check in Sema
---
clang/lib/Sema/SemaDecl.cpp | 35 +++++++++++++++++++----------------
1 file changed, 19 insertions(+), 16 deletions(-)
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 362df485a025c..3f3fea7e23814 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -13440,6 +13440,23 @@ bool
Sema::GloballyUniqueObjectMightBeAccidentallyDuplicated(
return true;
}
+// Determine whether the object seems mutable for the purpose of diagnosing
+// possible unique object duplication, i.e. non-const-qualified, and
+// not an always-constant type like a function.
+// Not perfect: doesn't account for mutable members, for example, or
+// elements of container types.
+// For nested pointers, any individual level being non-const is sufficient.
+bool looksMutable(QualType T, const ASTContext &Ctx) {
+ T = T.getNonReferenceType();
+ if (T->isFunctionType())
+ return false;
+ if (!T.isConstant(Ctx))
+ return true;
+ if (T->isPointerType())
+ return looksMutable(T->getPointeeType(), Ctx);
+ return false;
+}
+
void Sema::DiagnoseUniqueObjectDuplication(const VarDecl *VD) {
// If this object has external linkage and hidden visibility, it might be
// duplicated when built into a shared library, which causes problems if it's
@@ -13454,24 +13471,10 @@ void Sema::DiagnoseUniqueObjectDuplication(const
VarDecl *VD) {
!VD->isTemplated() &&
GloballyUniqueObjectMightBeAccidentallyDuplicated(VD)) {
- // Check mutability. For pointers, ensure that both the pointer and the
- // pointee are (recursively) const.
- QualType Type = VD->getType().getNonReferenceType();
- if (!Type.isConstant(VD->getASTContext())) {
+ QualType Type = VD->getType();
+ if (looksMutable(Type, VD->getASTContext())) {
Diag(VD->getLocation(), diag::warn_possible_object_duplication_mutable)
<< VD;
- } else {
- while (Type->isPointerType()) {
- Type = Type->getPointeeType();
- if (Type->isFunctionType())
- break;
- if (!Type.isConstant(VD->getASTContext())) {
- Diag(VD->getLocation(),
- diag::warn_possible_object_duplication_mutable)
- << VD;
- break;
- }
- }
}
// To keep false positives low, only warn if we're certain that the
>From 2e9bafe0191e9c9c694d5bb70e188607daae8bf5 Mon Sep 17 00:00:00 2001
From: Devon Loehr <dlo...@google.com>
Date: Thu, 20 Feb 2025 15:20:06 +0000
Subject: [PATCH 2/3] Add test
---
clang/test/SemaCXX/unique_object_duplication.h | 3 +++
1 file changed, 3 insertions(+)
diff --git a/clang/test/SemaCXX/unique_object_duplication.h
b/clang/test/SemaCXX/unique_object_duplication.h
index a59a8f91da8b8..861175766db70 100644
--- a/clang/test/SemaCXX/unique_object_duplication.h
+++ b/clang/test/SemaCXX/unique_object_duplication.h
@@ -99,6 +99,9 @@ inline void has_thread_local() {
thread_local int disallowedThreadLocal = 0; // hidden-warning
{{'disallowedThreadLocal' may be duplicated when built into a shared library:
it is mutable, has hidden visibility, and external linkage}}
}
+// Functions themselves are always immutable, so referencing them is okay
+inline auto& allowedFunctionReference = has_static_locals_external;
+
} // namespace StaticLocalTest
/******************************************************************************
>From be5482201c6d5004cc0a2cf48d1941f45905f5e7 Mon Sep 17 00:00:00 2001
From: Devon Loehr <dlo...@google.com>
Date: Fri, 21 Feb 2025 15:18:29 +0000
Subject: [PATCH 3/3] Make function static
---
clang/lib/Sema/SemaDecl.cpp | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 3f3fea7e23814..7633651337aa3 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -13446,7 +13446,7 @@ bool
Sema::GloballyUniqueObjectMightBeAccidentallyDuplicated(
// Not perfect: doesn't account for mutable members, for example, or
// elements of container types.
// For nested pointers, any individual level being non-const is sufficient.
-bool looksMutable(QualType T, const ASTContext &Ctx) {
+static bool looksMutable(QualType T, const ASTContext &Ctx) {
T = T.getNonReferenceType();
if (T->isFunctionType())
return false;
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