[Bug c++/82906] New: thread_local address not uniqued across shared libraries

[rafael.espindola at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82906

            Bug ID: 82906
           Summary: thread_local address not uniqued across shared
                    libraries
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rafael.espindola at gmail dot com
  Target Milestone: ---

Given

test.h:
inline int *foo() {                                                           
  static thread_local int i = 42;                                             
  return &i;                                                                  
}   

test.cpp:
#include "test.h"                                                             
int *bar() { return foo(); } 

test2.cpp:
#include "test.h"
#include <stdio.h>
int *bar();
int main() {
  printf("%d\n", bar() == foo());
  return 0;
}

If test.cpp is compiled with "gcc -c -O2 -fPIC test.c", the resulting .o has a
R_X86_64_TLSLD R_X86_64_DTPOFF32 pair.

Compiling the rest of the program with

g++ test.o -shared -o test.so"
g++ test2.cpp test.so -o t  -Wl,-rpath="\$ORIGIN"

produces an executable that prints 0 when run. It should print 1, that is,
bar() and foo() should find the same address.

Changing test.o to use general dynamic instead of local dynamic solves the
problem.