[Bug c++/100641] New: Link error when using extern thread_local variables on AIX

[Bug c++/100641] New: Link error when using extern thread_local variables on AIX

[mfarazma.ext at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100641

            Bug ID: 100641
           Summary: Link error when using extern thread_local variables on
                    AIX
           Product: gcc
           Version: 8.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: mfarazma.ext at gmail dot com
  Target Milestone: ---

Declaring a variable as "extern thread_local" in a C++ program leads to:

"ERROR: Undefined symbol: TLS init function for ..." during linking.

To reproduce:

file `0.cc`:
```
extern thread_local int foo;

int main(){
 return foo;
}
```

file `1.cc`:
```
thread_local int foo = 1; 
```

Then compile with `g++ 0.cc 1.cc` which produces this error:
```
ld: 0711-317 ERROR: Undefined symbol: TLS init function for foo
ld: 0711-317 ERROR: Undefined symbol: .TLS init function for foo
ld: 0711-317 ERROR: Undefined symbol: __get_tpointer
ld: 0711-345 Use the -bloadmap or -bnoquiet option to obtain more information.
collect2: error: ld returned 8 exit status
```

[Bug c++/100641] Link error when using extern thread_local variables on AIX

[mfarazma.ext at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100641

--- Comment #1 from m farazma <mfarazma.ext at gmail dot com> ---
Issue seems to be similar to this older gcc bug:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59364

[Bug target/100641] Link error when using extern thread_local variables on AIX

[hstong at ca dot ibm.com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100641

Hubert Tong <hstong at ca dot ibm.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |hstong at ca dot ibm.com

--- Comment #2 from Hubert Tong <hstong at ca dot ibm.com> ---
This was addressed in Clang last year. The AIX linker does not have the same
weak reference semantics as some other linkers. The means that the TLS init
function needs to be defined by the object file containing the definition of
the `thread_local` variable if the language semantics does not make it so that
all potential references occur in contexts where it is known that the
initialization/finalization is constant.

[Bug target/100641] Link error when using extern thread_local variables on AIX

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100641

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |DUPLICATE
             Status|UNCONFIRMED                 |RESOLVED

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Dup.

*** This bug has been marked as a duplicate of bug 93146 ***