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[C++20] [Modules] Don't add discardable variables to module initializers (#186752)

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Close https://github.com/llvm/llvm-project/issues/170099

The root cause of the problem is, we shouldn't add the inline variable
(which is discardable in linker's point of view) to the module's
initializers.

I verified with GCC's generated code to make the behavior consistent.

This is also a small optimization by the way.
This commit is contained in:
Chuanqi Xu 2026-03-16 17:05:33 +08:00 committed by GitHub
parent f894e8e92d
commit 87f1a2be75
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2 changed files with 24 additions and 1 deletions
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5
clang/lib/Sema/SemaDecl.cpp
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@ -15138,7 +15138,10 @@ void Sema::CheckCompleteVariableDeclaration(VarDecl *var) {
// If this variable must be emitted, add it as an initializer for the current
// module.
if (Context.DeclMustBeEmitted(var) && !ModuleScopes.empty())
if (Context.DeclMustBeEmitted(var) && !ModuleScopes.empty() &&
(ModuleScopes.back().Module->isHeaderLikeModule() ||
// For named modules, we may only emit non discardable variables.
!isDiscardableGVALinkage(Context.GetGVALinkageForVariable(var))))
Context.addModuleInitializer(ModuleScopes.back().Module, var);
// Build the bindings if this is a structured binding declaration.

20
clang/test/Modules/pr170099.cppm Normal file
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@ -0,0 +1,20 @@
// RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++26 -O3 -emit-llvm %s -o - | FileCheck %s
module;
struct A {};
struct B {
int x;
A a;
constexpr B(char *) { x = int(); }
~B();
};
struct C {
B b = "";
} inline c{};
export module foo;
// Just to make sure it won't crash
// CHECK: @_ZGIW3foo