https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119527
Bug ID: 119527
Summary: [modules] Internal linkage virtual key function of
template in header unit is not emitted
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:
// header.hpp
namespace {
template <typename T> struct S {
virtual void key() {}
};
S<int> s;
}
// main.cpp
import "header.hpp";
int main() {}
$ g++-15 -fmodule-header header.hpp
header.hpp:3:18: warning: ‘void {anonymous}::S<T>::key() [with
<template-parameter-1-1> = int]’ used but never defined
3 | virtual void key() {}
| ^~~
$ g++-15 -fmodules -fno-module-lazy main.cpp
/usr/bin/ld: /tmp/cc5etnIe.o:(.rodata+0x10): undefined reference to `(anonymous
namespace)::S<int>::key()'
collect2: error: ld returned 1 exit status
The issue seems to be related to header modules skipping much of
'c_parse_final_cleanups', since by not emitting vtables there they sometimes
miss instantiating template bodies, which leads to not only a confusing-looking
warning when building the header but also results in the body never being
emitted confusing importers as well.
Referenced Bugs:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103524
[Bug 103524] [meta-bug] modules issue
