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

[Media Tools]

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

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