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From: "roland at gnu dot org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug other/63758] New: liblto_plugin.so has undefined reference to _environ on OSX
Date: Thu, 06 Nov 2014 00:14:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63758

            Bug ID: 63758
           Summary: liblto_plugin.so has undefined reference to _environ
                    on OSX
           Product: gcc
           Version: 4.9.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: other
          Assignee: unassigned at gcc dot gnu.org
          Reporter: roland at gnu dot org
              Host: x86_64-apple-darwin
             Build: x86_64-apple-darwin11.4.2

Failure mode:

.../bin/../lib/gcc/.../4.9.2/../../../../.../bin/ld:
.../bin/../libexec/gcc/.../4.9.2/liblto_plugin.so: error loading plugin:
dlopen(.../bin/../libexec/gcc/.../4.9.2/liblto_plugin.so, 2): Symbol not found:
_environ
  Referenced from: .../bin/../libexec/gcc/.../4.9.2/liblto_plugin.so
  Expected in: flat namespace
 in .../bin/../libexec/gcc/.../4.9.2/liblto_plugin.so
collect2:error: ld returned 1 exit status

The references come from libiberty code (xmalloc.c and pex-unix.c).  Using
environ in a main program is fine, but it's documented on OSX that you
cannot use it from a shared library.  Instead, you must call the
_NSGetEnviron function to return its address (which also works just as well
in a main program).

I have a working fix which I'll attach shortly.