[Bug c++/77285] [5/6/7 Regression] extern thread_local linkage

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77285

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Reduced:

cat >a.cpp <<EOF
struct __attribute__((abi_tag("tag"))) X { ~X() { }int i = 0; };
thread_local X gFeelingLucky;
EOF

cat >main.cpp <<EOF
struct __attribute__((abi_tag("tag"))) X { ~X() { }int i = 0; };
extern thread_local X gFeelingLucky;

int main() {
 return gFeelingLucky.i;
}
EOF

g++ main.cpp a.cpp
/tmp/ccTyHWNr.o: In function `TLS wrapper function for gFeelingLucky':
main.cpp:(.text._ZTW13gFeelingLucky[_ZTW13gFeelingLucky]+0x5): undefined
reference to `TLS init function for gFeelingLucky'
collect2: error: ld returned 1 exit status

nm a.o 
                 U _GLOBAL_OFFSET_TABLE_
0000000000000000 B _Z13gFeelingLuckyB5cxx11
                 U _ZNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEC1Ev
                 U _ZNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEED1Ev
0000000000000000 r _ZStL19piecewise_construct
0000000000000000 T _ZTH13gFeelingLuckyB5cxx11
                 U __cxa_thread_atexit
                 U __dso_handle
0000000000000020 b __tls_guard
0000000000000000 t __tls_init

nm main.o
                 U _GLOBAL_OFFSET_TABLE_
                 U _Z13gFeelingLuckyB5cxx11
                 U
_ZNKSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEE6lengthEv
0000000000000000 r _ZStL19piecewise_construct
                 U _ZTH13gFeelingLucky
0000000000000000 W _ZTW13gFeelingLucky
0000000000000000 T main