Mercurial > sdl-ios-xcode
annotate docs/man3/SDL_SemTryWait.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 |
rev | line source |
---|---|
181
e5bc29de3f0a
Updated from the SDL Documentation Project
Sam Lantinga <slouken@libsdl.org>
parents:
55
diff
changeset
|
1 .TH "SDL_SemTryWait" "3" "Tue 11 Sep 2001, 23:00" "SDL" "SDL API Reference" |
0 | 2 .SH "NAME" |
3 SDL_SemTryWait\- Attempt to lock a semaphore but don\&'t suspend the thread\&. | |
4 .SH "SYNOPSIS" | |
5 .PP | |
6 \fB#include "SDL\&.h" | |
7 #include "SDL_thread\&.h" | |
8 .sp | |
9 \fBint \fBSDL_SemTryWait\fP\fR(\fBSDL_sem *sem\fR); | |
10 .SH "DESCRIPTION" | |
11 .PP | |
12 \fBSDL_SemTryWait\fP is a non-blocking varient of \fI\fBSDL_SemWait\fP\fR\&. If the value of the semaphore pointed to by \fBsem\fR is positive it will atomically decrement the semaphore value and return 0, otherwise it will return \fBSDL_MUTEX_TIMEOUT\fR instead of suspending the thread\&. | |
13 .PP | |
14 After \fBSDL_SemTryWait\fP is successful, the semaphore can be released and its count atomically incremented by a successful call to \fISDL_SemPost\fR\&. | |
15 .SH "RETURN VALUE" | |
16 .PP | |
17 Returns \fB0\fR if the semaphore was successfully locked or either \fBSDL_MUTEX_TIMEOUT\fR or \fB-1\fR if the thread would have suspended or there was an error, respectivly\&. | |
18 .PP | |
19 If the semaphore was not successfully locked, the semaphore will be unchanged\&. | |
20 .SH "EXAMPLES" | |
21 .PP | |
22 .PP | |
23 .nf | |
24 \f(CWres = SDL_SemTryWait(my_sem); | |
25 | |
26 if (res == SDL_MUTEX_TIMEOUT) { | |
27 return TRY_AGAIN; | |
28 } | |
29 if (res == -1) { | |
30 return WAIT_ERROR; | |
31 } | |
32 | |
33 \&.\&.\&. | |
34 | |
35 SDL_SemPost(my_sem);\fR | |
36 .fi | |
37 .PP | |
38 .SH "SEE ALSO" | |
39 .PP | |
40 \fI\fBSDL_CreateSemaphore\fP\fR, \fI\fBSDL_DestroySemaphore\fP\fR, \fI\fBSDL_SemWait\fP\fR, \fI\fBSDL_SemWaitTimeout\fP\fR, \fI\fBSDL_SemPost\fP\fR, \fI\fBSDL_SemValue\fP\fR | |
181
e5bc29de3f0a
Updated from the SDL Documentation Project
Sam Lantinga <slouken@libsdl.org>
parents:
55
diff
changeset
|
41 ...\" created by instant / docbook-to-man, Tue 11 Sep 2001, 23:00 |