[Bug c++/69775] New: thread_local extern variable causes linkage error

[saarraz2 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69775

            Bug ID: 69775
           Summary: thread_local extern variable causes linkage error
           Product: gcc
           Version: 5.3.0
            Status: UNCONFIRMED
          Severity: blocker
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: saarraz2 at gmail dot com
  Target Milestone: ---

I have code equivalent to the following:

foo.hpp:

    extern thread_local Foo foo;


foo.cpp:

    thread_local Foo foo;



I get a linkage error:

undefined reference to `TLS init function for hhh::util::format::start'
I've seen this bug referenced multiple times before - #55800 and #59364, both
of which happened 2 years ago and state that GCC version 4.9 had fixed the
problem, yet I'm getting the same problem with GCC 5.3! (through MINGW)