Mercurial > sdl-ios-xcode
view docs/man3/SDL_mutexP.3 @ 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> |
---|---|
date | Wed, 15 Mar 2006 15:47:49 +0000 |
parents | e5bc29de3f0a |
children | 546f7c1eb755 |
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.TH "SDL_mutexP" "3" "Tue 11 Sep 2001, 23:01" "SDL" "SDL API Reference" .SH "NAME" SDL_mutexP\- Lock a mutex .SH "SYNOPSIS" .PP \fB#include "SDL\&.h" #include "SDL_thread\&.h" .sp \fBint \fBSDL_mutexP\fP\fR(\fBSDL_mutex *mutex\fR); .SH "DESCRIPTION" .PP Locks the \fBmutex\fR, which was previously created with \fI\fBSDL_CreateMutex\fP\fR\&. If the mutex is already locked then \fBSDL_mutexP\fP will not return until it is \fIunlocked\fR\&. Returns \fB0\fR on success, or \fB-1\fR on an error\&. .PP SDL also defines a macro \fB#define SDL_LockMutex(m) SDL_mutexP(m)\fP\&. .SH "SEE ALSO" .PP \fI\fBSDL_CreateMutex\fP\fR, \fI\fBSDL_mutexV\fP\fR ...\" created by instant / docbook-to-man, Tue 11 Sep 2001, 23:01