Lenard René Dudfield wrote:
maybe it is memory alignment? Maybe the mmx/sse routines require 8 byte alignment or something? On Mon, Aug 18, 2008 at 4:55 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.
#include <stdio.h>
#include <stdlib.h>
#define SDL_revcpy(dst, src, len) \
do { \
int u0, u1, u2; \
char *dstp = (char *)(dst); \
char *srcp = (char *)(src); \
int n = (len); \
if ( n >= 4 ) { \
__asm__ __volatile__ ( \
"std\n\t" \
"rep ; movsl\n\t" \
: "=&c" (u0), "=&D" (u1), "=&S" (u2) \
: "0" (n >> 2), \
"1" (dstp+(n-4)), "2" (srcp+(n-4)) \
: "memory" ); \
} \
switch (n & 3) { \
case 3: dstp[2] = srcp[2]; \
case 2: dstp[1] = srcp[1]; \
case 1: dstp[0] = srcp[0]; \
break; \
default: \
break; \
} \
} while(0)
int main(int argc, char *argv[])
{
const int bufsize = 40;
const int padding = 8;
const int blocksize = 20;
char buffer[bufsize+1], *b;
int alignment, dstoffset, i;
buffer[bufsize] = 0; /* null terminated string */
for (alignment = 0; alignment < 4; ++alignment)
{
b = buffer + padding + alignment;
for (dstoffset = 0; dstoffset < 5; ++dstoffset)
{
for (i = 0; i < bufsize; ++i)
{
buffer[i] = '.';
}
for (i = 0; i < blocksize; ++i)
{
b[i] = 'a' + i;
}
printf("%s\n", buffer);
SDL_revcpy(b+dstoffset, b, blocksize);
printf("%s\n\n", buffer);
}
}
/* system("PAUSE"); */
return 0;
}