[Bug debug/85176] ICE in force_decl_die, at dwarf2out.c:25910

["marxin at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85176

--- Comment #4 from Martin Liška <marxin at gcc dot gnu.org> ---
Hmmm, reduced with missing return value:

$ cat ice.ii
namespace a {
class b &operator<<(b &, char *) {}
extern b c;
} // namespace a
main() { a::c << ""; }

$ g++ -O1 -flto -g1 ice.ii
ice.ii: In function ‘a::b& a::operator<<(a::b&, char*)’:
ice.ii:2:35: warning: no return statement in function returning non-void
[-Wreturn-type]
 class b &operator<<(b &, char *) {}
                                   ^
ice.ii: At global scope:
ice.ii:5:6: warning: ISO C++ forbids declaration of ‘main’ with no type
[-Wreturn-type]
 main() { a::c << ""; }
      ^
ice.ii: In function ‘int main()’:
ice.ii:5:18: warning: ISO C++ forbids converting a string constant to ‘char*’
[-Wwrite-strings]
 main() { a::c << ""; }
                  ^~
lto1: internal compiler error: in force_decl_die, at dwarf2out.c:25910
0x858808 force_decl_die
        ../../gcc/dwarf2out.c:25910
0x8596c7 flush_limbo_die_list
        ../../gcc/dwarf2out.c:30951
0x8663c5 dwarf2out_finish
        ../../gcc/dwarf2out.c:30991
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.
lto-wrapper: fatal error: g++ returned 1 exit status
compilation terminated.
/usr/bin/ld: error: lto-wrapper failed
collect2: error: ld returned 1 exit status

That started with my r254437. Let me isolate also a test-case without the
warning.