RE: [Qemu-devel] qemu dsound and crash

[ZIGLIO, Frediano, VF-IT]

> 
> ZIGLIO, Frediano wrote:
> 
> >I analyzed the dsound problem (using Windows dsound audio 
> driver cause
> >crash when closing console window cf "Qemu impressions"). 
> The problem is
> >very complicated. Is seems that for some reasons dsound dll 
> is unloaded
> >before msvcrt (which hold atexit and exit function) so dsound free
> >memory then msvcrt calls at exit callbacks which try to access freed
> >structure... The problem occur on Windows XP and I got error 
> using Qemu
> >downloaded at http://www.h7.dion.ne.jp/~qemu-win/ and compiling 0.8.1
> >from sources. dsound.dll is loaded calling CoCreateInstance in
> >audio/dsoundaudio.c (line 975) however is very strange this dll free
> >cause even dsound.dll depends on msvcrt.dll. Perhaps a 
> workaround can be
> >to call SetConsoleCtrlHandler on main and calling exit by 
> our own... I
> >noted that for some reason qemu.exe seems to load msvcrt.dll two
> >times...
> 
> Thanks for your info. I wondered what caused the problem. It 
> seems that
> optimization also have effect on the problem.
> 
> Regards,
> Kazu
> 

Thanks,
  at least I know someone read my mails :)

Well... how I discovered the cause
- launched qemu, closing with "X" crash
- I compiled qemu (without dsound support) and accidentally "X" works...
- after recompiling with dsound + fmod qemu crash with "X"
- now what cause the error

---------------------------
qemu.exe - Application Error
---------------------------
The instruction at "0x00438213" referenced memory at "0x0b112210". The
memory could not be "read". 
Click on OK to terminate the program
---------------------------
OK   
---------------------------
- 0x00438213 is in dsoundaudio.c (enabled mapfile on linker to discover
this)
- I added many printf and discovered that problem was dsound->Release()
- added others printf, Release is not called two times
- opened debugger and placed a break point on access of 0x0b112210
(after DSound creation)
- memory change in a HeapFree called from dsound.DllMain from
ntdll.LdrShutdownProcess from kernel32

What did I do next (today) ? I didn't understand why qemu.exe imports
msvcrt two times... I linked with --verbose flags and I noted that some
libraries are linked twice but removing these duplications have no
effects (as I expected). I noted that -lmsvcrt and -lmoldname are linked
together. This caused some problems in another project some time ago so
I decided to remove -lmoldname... after a lot of replacement in sources
(like open -> _open, read -> _read and so on) I got it linked with one
msvcrt import from qemu.exe, but this not solve initial problem... so
this is not the cause... I can confirm that my workaround works fine but
I'm unable to explain the dsound problem... why the hell should windows
free dsound before msvcrt?

freddy77