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Re: [pygame] Another blitting surface to itself crash

Thanks Nicholas,
That is kind of interesting, and kind of confusing. Hugo Arts got a Pygame parachute on XP that was traced to SDL itself. I get a Fatal Python error, as do you. But unless you use a vintage Windows system as I do then it would seem the type of error is independent of Windows version. It behaves as a memory violation, but where. And it is MinGW specific.
I ran gdb on a small C program that does a self blit. I saw no place where pointers go astray. The obvious way in which MinGW and VC code differs is some inline assembly happens with MinGW. But a test on the inlined assembly code involved with an overlapping blit showed no problems. I must be making a faulty assumption somewhere. 

Lenard


Nicholas Dudfield wrote:

Lenard,

"Fatal Python error: Inconsistent interned string state."
On Mon, Aug 18, 2008 at 8:17 AM, Lenard Lindstrom <len-l@xxxxxxxxx <mailto:len-l@xxxxxxxxx>> wrote: 

    Yes, debug print statements show the crash happens when the SDL
    blit funcion SDL_BlitSurface is called. Did you get a Pygame
    parachute or a Python interned string violation?

    Lenard


    Nicholas Dudfield wrote:

        Ok, I have been informed there is are PyGame blits not derived
        from SDL, so that explains that.

        {pygame_AlphaBlit, pygame_Blit} from clip above looks like

        Seems oblivious (sic) now it's pointed out.


        On Sat, Aug 16, 2008 at 4:37 PM, Nicholas Dudfield
        <ndudfield@xxxxxxxxx <mailto:ndudfield@xxxxxxxxx>
        <mailto:ndudfield@xxxxxxxxx <mailto:ndudfield@xxxxxxxxx>>> wrote:

           I had a little play with the test_blit_to_self.py:
           SDL VERSION:

           1.2.13 prebuilts

           PYGAME:

           Mingw compiled, svn r 1619

           OBSERVATIONS:

           Unmodified the test wouldn't run at all as noted earlier.

           I don't know if it's any help but I noticed after
        commenting out
           the "blitting screen to self" section that I could get the
           "blitting surface to self" test and "blitting surface to
        screen"
           to run the full 100 cycles if I instantiated the Surface
        `a` with
           pygame.SRCALPHA flags.

           Also, if using BLEND_RGB_ADD flags "blitting screen to self"
           worked. Also screen.copy() worked as a source... but eh.

           CONCLUSIONS:

           s.blit(s, (0,0)) works if SRCALPHA bits set for s
           screen.blit(screen, step, None, pygame.BLEND_RGB_ADD)

           Is that any help for you guys in debugging?? I have no C-fu
        or I
           would have a tinker myself.






--
Lenard Lindstrom
<len-l@xxxxxxxxx>