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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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>SDL_Rect</TITLE
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>SDL_Rect</H1
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><H2
>Name</H2
>SDL_Rect&nbsp;--&nbsp;Defines a rectangular area</DIV
><DIV
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><H2
>Structure Definition</H2
><PRE
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>typedef struct{
  Sint16 x, y;
  Uint16 w, h;
} SDL_Rect;</PRE
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><TT
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><I
>x, y</I
></TT
></TD
><TD
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>Position of the upper-left corner of the rectangle</TD
></TR
><TR
><TD
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><TT
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><I
>w, h</I
></TT
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><TD
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>The width and height of the rectangle</TD
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><H2
>Description</H2
><P
>A <SPAN
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>SDL_Rect</SPAN
> defines a rectangular area of pixels. It is used by <A
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><TT
CLASS="FUNCTION"
>SDL_BlitSurface</TT
></A
> to define blitting regions and by several other video functions.</P
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><TT
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>SDL_BlitSurface</TT
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>,
<A
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>SDL_UpdateRect</TT
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