https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118846
Bug ID: 118846
Summary: [modules] Unbound template arguments considered
TU-local
Product: gcc
Version: 15.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: nshead at gcc dot gnu.org
Blocks: 103524
Target Milestone: ---
Consider the following snippets:
export module A;
template <int> struct integral_constant;
template <template <class> class> constexpr int cx_count_if() { return 0; }
template <template <class> class P> struct mp_count_if_impl {
using type = integral_constant<cx_count_if<P>()>;
};
and
export module B;
template <template <class> class> struct consume;
template <class P> struct use {
using type = consume<P::template fn>;
};
These cases complain about 'P' and 'P::template fn' being TU-local,
respectively, which doesn't really make sense for template parameters.
'g++ -fmodules -S a.cpp':
a.cpp:5:9: error: ‘template<template<class> class P> using
mp_count_if_impl<P>::type = integral_constant<cx_count_if<P>()>’ exposes
TU-local entity ‘struct integral_constant<cx_count_if<P>()>’
5 | using type = integral_constant<cx_count_if<P>()>;
| ^~~~
a.cpp:2:23: note: ‘struct integral_constant<cx_count_if<P>()>’ declared with
internal linkage
2 | template <int> struct integral_constant;
| ^~~~~~~~~~~~~~~~~
'g++ -fmodules -S b.cpp':
b.cpp:4:9: error: ‘template<class P> using use<P>::type = consume<P::template
fn>’ exposes TU-local entity ‘struct consume<P::template fn>’
4 | using type = consume<P::template fn>;
| ^~~~
b.cpp:2:42: note: ‘struct consume<P::template fn>’ has TU-local template
argument ‘P::template fn’
2 | template <template <class> class> struct consume;
| ^~~~~~~
b.cpp:4:36: note: ‘P::template fn’ declared with internal linkage
4 | using type = consume<P::template fn>;
| ^~
It's also worth noting that with '-fconcepts', having any other declaration
with a constraint (e.g. adding 'requires true' to 'consume') will cause a
segfault during diagnostic printing for B.
Referenced Bugs:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103524
[Bug 103524] [meta-bug] modules issue
