[Sumover-dev] Re: [Media Tools] #183: VIC H.264 crashing on startup in avcodec.dll

[Media Tools]

#183: VIC H.264 crashing on startup in avcodec.dll
---------------------+------------------------------------------------------
  Reporter:  piers   |       Owner:  piers       
      Type:  defect  |      Status:  closed      
  Priority:  major   |   Milestone:              
 Component:  vic     |     Version:  2.8ucl-1.4.0
Resolution:  fixed   |    Keywords:              
---------------------+------------------------------------------------------
Old description:

> VIC was crashing on startup in __gcc_register_frame() - having been
> called by__do_global_ctors () and by DllMainCRTStartup at 12 () when the dll
> is loaded. Had to debug in gdb - after tracking the original crash in
> from Visual C++ but since VC++ can't read the debug info generated by
> mingw I ran it in mingw gdb. It seems that gdb can use the symbol
> information from VC++ (which setup in VC++ using the Microsoft symbol
> server: http://msdl.microsoft.com/download/symbols)
>
> It turns out the problem was the same as [http://www.nabble.com/Bad-DLL-
> relocation---reproducible-w--test-case-tt18292380.html#a18292380 this
> project] was having:
> "The problem is that DLLs generated by MingW GCC (with -shared) are not
> correctly relocatable, even though they contain relocation information.
> LoadLibrary() returns ERROR_NOACCESS if it is forced to relocate the DLL
> and a backtrace shows a blind jump into bad memory from
> __gcc_register_frame. "
>
> "* The crash is caused by the weak reference __register_frame_info being
> given an out-of-segment pointer (0x9dae0000) in the relocated DLL. I
> presume fixup has gone wrong?
>
> * This is not an issue with GCC 4.2.1-SJLJ, likely due to the SJLJ
> unwind model, which uses different code in __gcc_register_frame.
> However, I was unable to find the 4.2.1-DW2 package to confirm this. "
>
> This avcodec.dll library had been compiled with mingw gcc-4.3.0-alpha -
> It was fixed by compiling it with GCC 4.2.1-SJLJ.

New description:

 VIC was crashing on startup in !__gcc_register_frame() - having been
 called by !__do_global_ctors () and by DllMainCRTStartup at 12 () when the
 dll is loaded. Had to debug in gdb - after tracking the original crash in
 from Visual C++ but since VC++ can't read the debug info generated by
 mingw I ran it in mingw gdb. It seems that gdb can use the symbol
 information from VC++ (which setup in VC++ using the Microsoft symbol
 server: http://msdl.microsoft.com/download/symbols)

 It turns out the problem was the same as [http://www.nabble.com/Bad-DLL-
 relocation---reproducible-w--test-case-tt18292380.html#a18292380 this
 project] was having:
   The problem is that DLLs generated by MingW GCC (with -shared) are not
 correctly relocatable, even though they contain relocation information.
 LoadLibrary() returns ERROR_NOACCESS if it is forced to relocate the DLL
 and a backtrace shows a blind jump into bad memory from
 !__gcc_register_frame.

     * The crash is caused by the weak reference !__register_frame_info
 being given an out-of-segment pointer (0x9dae0000) in the relocated DLL. I
 presume fixup has gone wrong?

     * This is not an issue with GCC 4.2.1-SJLJ, likely due to the SJLJ
 unwind model, which uses different code in !__gcc_register_frame. However,
 I was unable to find the 4.2.1-DW2 package to confirm this.

 VIC's avcodec.dll library had been compiled with mingw gcc-4.3.0-alpha -
 It was fixed by compiling it with GCC 4.2.1-SJLJ.

-- 
Ticket URL: <https://frostie.cs.ucl.ac.uk/nets/mmedia/ticket/183>
Media Tools <http://mediatools.cs.ucl.ac.uk/>
Media Tools