[Bug middle-end/50598] [4.7 Regression] Undefined symbols: "___emutls_v.*", ... on *-apple-darwin*

[iains at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50598

--- Comment #7 from Iain Sandoe <iains at gcc dot gnu.org> 2011-11-03 18:22:05 UTC ---
$ more ../gcc-live-trunk/libgomp/testsuite/libgomp.c++/pr24455-1.C 
// { dg-do compile }
// { dg-require-effective-target tls }
extern int i;
#pragma omp threadprivate (i)

int i;

===
if this is compiled with  "-x c "  we get:

$ more pr24455-1.s         .text
__GLOBAL__sub_I_65535_0_pr24455_1.C:
        pushl   %ebx
        subl    $24, %esp
        call    ___x86.get_pc_thunk.bx
L00000000001$pb:
        movl    $0, 12(%esp)
        movl    $4, 8(%esp)
        movl    $4, 4(%esp)
        movl    L___emutls_v.i$non_lazy_ptr-L00000000001$pb(%ebx), %eax
        movl    %eax, (%esp)
        call    ___emutls_register_common
        addl    $24, %esp
        popl    %ebx
        ret
        .mod_init_func
        .align 2
        .long   __GLOBAL__sub_I_65535_0_pr24455_1.C
        .comm   ___emutls_v.i,16,2
        .section __TEXT,__textcoal_nt,coalesced,pure_instructions
        .weak_definition        ___x86.get_pc_thunk.bx
        .private_extern ___x86.get_pc_thunk.bx
___x86.get_pc_thunk.bx:
        movl    (%esp), %ebx
        ret
        .section __IMPORT,__pointers,non_lazy_symbol_pointers
L___emutls_v.i$non_lazy_ptr:
        .indirect_symbol ___emutls_v.i
        .long   0
        .subsections_via_symbols

====

if compiled with g++ we get an empty body (as per comment #4).

the tree-dumps are not very interesting - because the tu shows as empty ...

I'm guessing that somehow g++ is dropping the extern .. which allows the
revised version of cgraphunit to prune the variable .. but I'm not sure how to
go about debugging this at the moment ...