Mercurial > sdl-ios-xcode
comparison src/video/SDL_blit_N.c @ 1544:ab1e4c41ab71
Fixed bug #33
Mike Frysinger wrote:
> with libsdl-1.2.9, some games (like bomberclone) started
> segfaulting in Gentoo
[...snip...]
> the last change in the last hunk:
[...snip...]
> if i change the statement to read:
> (table[which].blit_features & GetBlitFeatures()) == GetBlitFeatures()
> bomberclone no longer segfaults on my box
Alex Volkov wrote:
> The test "(table[which].blit_features & GetBlitFeatures()) ==
> table[which].blit_features)" is correct, and the previous
> "(table[which].cpu_mmx == SDL_HasMMX())" was actually broken.
I think there is potentially a slightly different cause of the above problem.
During the introduction of the Altivec code, the blit_table struct field
'alpha' got changed from a straightforward enum to a bitmask, which makes
perfect sense by itself. However, now the table driven blitter selection code
in SDL_CalculateBlitN() can choose the wrong blitters when searching for a
NO_ALPHA blitter because of the following code:
int a_need = 0;
...
(a_need & table[which].alpha) == a_need &&
When searching through the normal_blit_2[] table, a SET_ALPHA blitter (like
Blit_RGB565_ARGB8888) can now be selected instead of a NO_ALPHA one, causing
alpha channel bits to appear in a non-alpha destination surface. I suppose this
could theoretically be an indirect cause of the segfault mentioned above.
I *think* this can be fixed by changing to
int a_need = NO_ALPHA;
author | Sam Lantinga <slouken@libsdl.org> |
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date | Wed, 15 Mar 2006 15:47:49 +0000 |
parents | 98f9b16f565c |
children | 14717b52abc0 |
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1543:98f9b16f565c | 1544:ab1e4c41ab71 |
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2431 } else { | 2431 } else { |
2432 blitfun = BlitNto1; | 2432 blitfun = BlitNto1; |
2433 } | 2433 } |
2434 } else { | 2434 } else { |
2435 /* Now the meat, choose the blitter we want */ | 2435 /* Now the meat, choose the blitter we want */ |
2436 int a_need = 0; | 2436 int a_need = NO_ALPHA; |
2437 if(dstfmt->Amask) | 2437 if(dstfmt->Amask) |
2438 a_need = srcfmt->Amask ? COPY_ALPHA : SET_ALPHA; | 2438 a_need = srcfmt->Amask ? COPY_ALPHA : SET_ALPHA; |
2439 table = normal_blit[srcfmt->BytesPerPixel-1]; | 2439 table = normal_blit[srcfmt->BytesPerPixel-1]; |
2440 for ( which=0; table[which].dstbpp; ++which ) { | 2440 for ( which=0; table[which].dstbpp; ++which ) { |
2441 if ( MASKOK(srcfmt->Rmask, table[which].srcR) && | 2441 if ( MASKOK(srcfmt->Rmask, table[which].srcR) && |