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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 355632dca928
children
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<HTML
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><TITLE
>SDL_InitSubSystem</TITLE
><META
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>SDL_InitSubSystem</H1
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><H2
>Name</H2
>SDL_InitSubSystem&nbsp;--&nbsp;Initialize subsystems</DIV
><DIV
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><H2
>Synopsis</H2
><DIV
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><P
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><PRE
CLASS="FUNCSYNOPSISINFO"
>#include "SDL.h"</PRE
><P
><CODE
><CODE
CLASS="FUNCDEF"
>int <B
CLASS="FSFUNC"
>SDL_InitSubSystem</B
></CODE
>(Uint32 flags);</CODE
></P
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><H2
>Description</H2
><P
>After SDL has been initialized with <A
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><TT
CLASS="FUNCTION"
>SDL_Init</TT
></A
> you may initialize uninitialized subsystems with <TT
CLASS="FUNCTION"
>SDL_InitSubSystem</TT
>. The <TT
CLASS="PARAMETER"
><I
>flags</I
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> parameter is the same as that used in <A
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CLASS="FUNCTION"
>SDL_Init</TT
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>.</P
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><A
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><H2
>Examples</H2
><PRE
CLASS="PROGRAMLISTING"
>/* Seperating Joystick and Video initialization. */
SDL_Init(SDL_INIT_VIDEO);
.
.
SDL_SetVideoMode(640, 480, 16, SDL_DOUBLEBUF|SDL_FULLSCREEN);
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/* Do Some Video stuff */
.
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/* Initialize the joystick subsystem */
SDL_InitSubSystem(SDL_INIT_JOYSTICK);

/* Do some stuff with video and joystick */
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.
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/* Shut them both down */
SDL_Quit();</PRE
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