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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 ><HEAD ><TITLE >SDL_VideoDriverName</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+ "><LINK REL="HOME" TITLE="SDL Library Documentation" HREF="index.html"><LINK REL="UP" TITLE="Video" HREF="video.html"><LINK REL="PREVIOUS" TITLE="SDL_GetVideoInfo" HREF="sdlgetvideoinfo.html"><LINK REL="NEXT" TITLE="SDL_ListModes" HREF="sdllistmodes.html"></HEAD ><BODY CLASS="REFENTRY" BGCOLOR="#FFF8DC" TEXT="#000000" LINK="#0000ee" VLINK="#551a8b" ALINK="#ff0000" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="3" ALIGN="center" >SDL Library Documentation</TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="bottom" ><A HREF="sdlgetvideoinfo.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" ></TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="sdllistmodes.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><H1 ><A NAME="SDLVIDEODRIVERNAME" ></A >SDL_VideoDriverName</H1 ><DIV CLASS="REFNAMEDIV" ><A NAME="AEN1127" ></A ><H2 >Name</H2 >SDL_VideoDriverName -- Obtain the name of the video driver</DIV ><DIV CLASS="REFSYNOPSISDIV" ><A NAME="AEN1130" ></A ><H2 >Synopsis</H2 ><DIV CLASS="FUNCSYNOPSIS" ><A NAME="AEN1131" ></A ><P ></P ><PRE CLASS="FUNCSYNOPSISINFO" >#include "SDL.h"</PRE ><P ><CODE ><CODE CLASS="FUNCDEF" >char *<B CLASS="FSFUNC" >SDL_VideoDriverName</B ></CODE >(char *namebuf, int maxlen);</CODE ></P ><P ></P ></DIV ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN1137" ></A ><H2 >Description</H2 ><P >The buffer pointed to by <TT CLASS="PARAMETER" ><I >namebuf</I ></TT > is filled up to a maximum of <TT CLASS="PARAMETER" ><I >maxlen</I ></TT > characters (include the NULL terminator) with the name of the initialised video driver. The driver name is a simple one word identifier like "x11" or "windib".</P ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN1142" ></A ><H2 >Return Value</H2 ><P >Returns <TT CLASS="LITERAL" >NULL</TT > if video has not been initialised with <TT CLASS="FUNCTION" >SDL_Init</TT > or a pointer to <TT CLASS="PARAMETER" ><I >namebuf</I ></TT > otherwise.</P ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN1148" ></A ><H2 >See Also</H2 ><P ><A HREF="sdlinit.html" ><TT CLASS="FUNCTION" >SDL_Init</TT ></A > <A HREF="sdlinitsubsystem.html" ><TT CLASS="FUNCTION" >SDL_InitSubSystem</TT ></A ></P ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="sdlgetvideoinfo.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="sdllistmodes.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >SDL_GetVideoInfo</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="video.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >SDL_ListModes</TD ></TR ></TABLE ></DIV ></BODY ></HTML >