[Vala] A seemingly impossible segfault.

[Michael Trausch <mike trausch us>]

I'm not entirely sure *where* in the stack the issue is.  I'm using
Vala 0.7.7, and when I compile the libvfcgi project I am receiving a
segfault at line 56 of http://is.gd/5mlyT -- however, a segfault there
should not be possible, as I understand it.  So, either I'm doing
something horribly wrong that I cannot see, or there's something
horribly wrong somewhere else that I cannot see.  Can anyone perhaps
tell me what I've done wrong?

The change that introduced the crash was the one wherein I initialized
and created the new object:

  http://bazaar.launchpad.net/~mtrausch/libvfcgi/trunk/revision/21/libvfcgi/server.vala

The thing I don't get is *why* that would crash at all.  GDB says:

Program received signal SIGSEGV, Segmentation fault.
0x00007ffff7bd73e6 in fast_cgi_server_construct (object_type=6330480,
error=0x7fffffffe1a0) at server.c:208
208             self->priv->m_mainloop = (_tmp0_ = g_main_loop_new (NULL, FALSE),
_g_main_loop_unref0 (self->priv->m_mainloop), _tmp0_);

Of course the problem there is that there are multiple statements and
I know not which one is actually crashing.  Looking at the
disassembly, I get:

000000000000d391 <fast_cgi_server_construct>:
    d391:       55                      push   %rbp
    d392:       48 89 e5                mov    %rsp,%rbp
    d395:       41 54                   push   %r12
    d397:       53                      push   %rbx
    d398:       48 81 ec b0 00 00 00    sub    $0xb0,%rsp
    d39f:       48 89 bd 58 ff ff ff    mov    %rdi,-0xa8(%rbp)
    d3a6:       48 89 b5 50 ff ff ff    mov    %rsi,-0xb0(%rbp)
    d3ad:       48 c7 45 e8 00 00 00    movq   $0x0,-0x18(%rbp)
    d3b4:       00
    d3b5:       bf 20 00 00 00          mov    $0x20,%edi
    d3ba:       e8 69 8d ff ff          callq  6128 <g_malloc0 plt>
    d3bf:       48 89 45 e0             mov    %rax,-0x20(%rbp)
    d3c3:       48 8b 45 e0             mov    -0x20(%rbp),%rax
    d3c7:       48 89 45 d8             mov    %rax,-0x28(%rbp)
    d3cb:       be 00 00 00 00          mov    $0x0,%esi
    d3d0:       bf 00 00 00 00          mov    $0x0,%edi
    d3d5:       e8 de 87 ff ff          callq  5bb8 <g_main_loop_new plt>
    d3da:       48 89 45 d0             mov    %rax,-0x30(%rbp)
    d3de:       48 8b 45 b8             mov    -0x48(%rbp),%rax
    d3e2:       48 8b 40 18             mov    0x18(%rax),%rax
    d3e6:       48 8b 00                mov    (%rax),%rax

0xd3e6 is the line that is causing it to crash, according to the backtrace.

I haven't the slightest how to follow it from there, so I am hoping
that someone here can see my error or provide some insight as to what
might be being done wrong.

    --- Mike