https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120005
Bug ID: 120005
Summary: TU-local exposure error in constexpr function
Product: gcc
Version: 15.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: marcel at laverdet dot com
Target Milestone: ---
I'm receiving a new TU-local exposure error under modules in gcc 15.1.0 which
didn't appear before in gcc 14. Minimal test case is below. This error only
occurs if the function declared in the header file is constexpr, the variable
can be const or constexpr.
root[18:56:11] [/workspace] $ cat a.h
constexpr int flag = 0;
constexpr bool check() {
return flag == 0;
}
root[18:57:41] [/workspace] $ cat a.cc
module;
#include "a.h"
export module M;
export using ::check;
root[18:57:54] [/workspace] $ gcc-14 -fmodules-ts -c a.cc
# it compiles fine
root[18:57:57] [/workspace] $ gcc-15 -fmodules-ts -c a.cc
In file included from a.cc:2:
a.h:2:16: error: 'constexpr bool check()' exposes TU-local entity 'flag'
2 | constexpr bool check() {
| ^~~~~
a.h:1:15: note: 'flag' declared with internal linkage
1 | constexpr int flag = 0;
| ^~~~
root[18:58:00] [/workspace] $ gcc-15 --version
gcc-15 (Debian 15.1.0-1) 15.1.0
Copyright (C) 2025 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
---
I'm additionally seeing errors in a module which internally uses some boost
containers. The case above is pared down from an unrelated header. The two
issues seem related but in the boost case the function is not constexpr. I
haven't had a chance to chop this up into a good reproduction but I thought I
would raise it here in case it's the same and I can save the time.
/usr/include/boost/container/vector.hpp:1305:3: error: ‘template<class T, class
A, class Options> boost::container::vector<T, Allocator,
Options>::vector(boost::container::vector<T, Allocator, Options>&&, const
allocator_type&)’ exposes TU-local entity
‘boost::container::vector_uninitialized_size’
1305 | vector(BOOST_RV_REF(vector) x, const allocator_type &a)
| ^~~~~~
/usr/include/boost/container/vector.hpp:325:49: note:
‘boost::container::vector_uninitialized_size’ declared with internal linkage
325 | static inline const vector_uninitialized_size_t
vector_uninitialized_size =
|
^~~~~~~~~~~~~~~~~~~~~~~~~
