libffi crashes libgobject when compiled without optimizations

libffi crashes libgobject when compiled without optimizations

[LRN]

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I'm using mingw.org i386 gcc 4.7.2
When i compile libffi with -O1, everything works fine.
If i replace "-O1" with " -O0 \
 -fauto-inc-dec \
 -fcompare-elim  \
 -fcprop-registers  \
 -fdce  \
 -fdefer-pop  \
 -fdelayed-branch  \
 -fdse  \
 -fguess-branch-probability  \
 -fif-conversion2  \
 -fif-conversion  \
 -fipa-pure-const  \
 -fipa-profile  \
 -fipa-reference  \
 -fmerge-constants \
 -fsplit-wide-types  \
 -ftree-bit-ccp  \
 -ftree-builtin-call-dce  \
 -ftree-ccp  \
 -ftree-ch  \
 -ftree-copyrename  \
 -ftree-dce  \
 -ftree-dominator-opts  \
 -ftree-dse  \
 -ftree-forwprop  \
 -ftree-fre  \
 -ftree-phiprop  \
 -ftree-sra  \
 -ftree-pta  \
 -ftree-ter \
 -funit-at-a-time \
 -fomit-frame-pointer \
"
(that is, -O0 and all the optimizations that -O1 enables)
libffi crashes when libgobject is unloaded.

The crash can be reproduced with this program:

#include <windows.h>
#include <stdio.h>

int
main (int argc, char **argv)
{
  HMODULE h;

  h = LoadLibraryA ("libgobject-2.0-0.dll");
  if (h == NULL)
    printf ("Failed to loadlib: %lu\n", GetLastError ());
  else
    FreeLibrary (h);
  return 0;
}

The version of glib doesn't matter much (anything released within last
couple of years will do, i think). The version of libffi doesn't
matter either (verified for the first commit after 3.0.10 (i.e. the
one that bumped the interface)).
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Re: libffi crashes libgobject when compiled without optimizations

[Anthony Green]

On Sat, Mar 9, 2013 at 7:39 AM, LRN <lrn1986@gmail.com> wrote:
> The crash can be reproduced with this program:
>

Are you able to generate a stack trace from the crash?

Thanks,

AG

Re: libffi crashes libgobject when compiled without optimizations

[LRN]

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On 16.03.2013 16:56, Anthony Green wrote:
> On Sat, Mar 9, 2013 at 7:39 AM, LRN <lrn1986@gmail.com> wrote:
>> The crash can be reproduced with this program:
>> 
> 
> Are you able to generate a stack trace from the crash?
> 

F:\src\mingw\bin>gdb --args testfficrash.exe
GNU gdb (GDB) 7.5
Copyright (C) 2012 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later
<http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "i686-pc-mingw32".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from F:\src\mingw\bin\testfficrash.exe...done.
(gdb) b abort
Breakpoint 1 at 0x401be8
(gdb) r
Starting program: F:\src\mingw\bin\testfficrash.exe
[New Thread 21652.0x5fa58]

Breakpoint 1, 0x6b74c9d0 in abort () from F:\src\mingw\bin\libffi-6.dll
(gdb) bt
#0  0x6b74c9d0 in abort () from F:\src\mingw\bin\libffi-6.dll
#1  0x6b74c6d6 in __deregister_frame_info_bases () from
F:\src\mingw\bin\libffi-6.dll
#2  0x6b741283 in __gcc_deregister_frame () from
F:\src\mingw\bin\libffi-6.dll
#3  0x6b741023 in __dll_exit () from F:\src\mingw\bin\libffi-6.dll
#4  0x6b7410ae in DllMainCRTStartup@12 () from
F:\src\mingw\bin\libffi-6.dll
#5  0x77a89950 in ntdll!RtlpNtMakeTemporaryKey () from
C:\Windows\system32\ntdll.dll
#6  0x6b740000 in ?? ()
#7  0x77aaacde in ntdll!TpCallbackIndependent () from
C:\Windows\system32\ntdll.dll
#8  0x6b741060 in __dll_exit () from F:\src\mingw\bin\libffi-6.dll
#9  0x00000000 in ?? ()

This is with 1.0.13-rc1
Not very useful, i know.

I've tried getting a list of symbols exported from libffi, and then
setting breakpoints on all of them, just to see what is being called.
Turns out, nothing is called, except for __deregister_frame_info_bases
(which crashes). Well, that is not precise. There are two functions
for which i can't set breakpoints, because gdb says they have the
address of 0x0. That's __register_frame_info and  __deregister_frame_info.

The libffi that is compiled with optimization does not have any weird
functions exported (just the ffi_*()).

My guess is that for -O0 libgcc is linked into libffi, which conflicts
with libgcc_s_dw2 (which is pulled by libintl, which, in turn, is
pulled by libglib, which is pulled by libgobject).

I've made another test program (attached, testcrash.c), and my
suspicions proved to be correct - it crashes. If i change the order in
which libraries are unloaded (free libffi first, then libgcc), gdb
throws some warnings around (about breakpoints) when stepping, but
otherwise program ends normally.

Why libintl links to libgcc is a question that's been bugging me for
some time now. It seems that now i have more incentives to find out
(that said, i still don't understand why libffi is linked to libgcc
when compiled with -O0).

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#include <windows.h>
#include <stdio.h>

int
main (int argc, char **argv)
{
  HMODULE h;
  HMODULE h2;

  h2 = LoadLibraryA ("libgcc_s_dw2-1.dll");
  h = LoadLibraryA ("libffi-6.dll");
  if ((h == NULL) || (h2 == NULL))
  {
    printf ("Failed to loadlib: %lu\n", GetLastError ());
  }
  else
  {
    FreeLibrary (h2);
    FreeLibrary (h);
  }
  return 0;
}