Re: [pygame] Another blitting surface to itself crash

["Brian Fisher" <brian@xxxxxxxxxxxxxxxxxxx>]

I've actually gotten both the interned string thing and a pygame parachute error in the same run

also, I still think the weird _strdup linkage is a good clue. I haven't had time to try myself, but I think compiling sdl with mingw with source modified to not call strdup ever will fix the problem.

On Sun, Aug 17, 2008 at 11:55 PM, Lenard Lindstrom <len-l@xxxxxxxxx> wrote:

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>