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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_CDOpen</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="CD-ROM" HREF="cdrom.html"><LINK REL="PREVIOUS" TITLE="SDL_CDName" HREF="sdlcdname.html"><LINK REL="NEXT" TITLE="SDL_CDStatus" HREF="sdlcdstatus.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="sdlcdname.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" ></TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="sdlcdstatus.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><H1 ><A NAME="SDLCDOPEN" ></A >SDL_CDOpen</H1 ><DIV CLASS="REFNAMEDIV" ><A NAME="AEN7274" ></A ><H2 >Name</H2 >SDL_CDOpen -- Opens a CD-ROM drive for access.</DIV ><DIV CLASS="REFSYNOPSISDIV" ><A NAME="AEN7277" ></A ><H2 >Synopsis</H2 ><DIV CLASS="FUNCSYNOPSIS" ><A NAME="AEN7278" ></A ><P ></P ><PRE CLASS="FUNCSYNOPSISINFO" >#include "SDL.h"</PRE ><P ><CODE ><CODE CLASS="FUNCDEF" >SDL_CD *<B CLASS="FSFUNC" >SDL_CDOpen</B ></CODE >(int drive);</CODE ></P ><P ></P ></DIV ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN7284" ></A ><H2 >Description</H2 ><P >Opens a CD-ROM drive for access. It returns a <A HREF="sdlcd.html" ><SPAN CLASS="STRUCTNAME" >SDL_CD</SPAN ></A > structure on success, or <TT CLASS="LITERAL" >NULL</TT > if the drive was invalid or busy. This newly opened CD-ROM becomes the default CD used when other CD functions are passed a <TT CLASS="LITERAL" >NULL</TT > CD-ROM handle. </P ><P >Drives are numbered starting with 0. Drive 0 is the system default CD-ROM.</P ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN7292" ></A ><H2 >Examples</H2 ><PRE CLASS="PROGRAMLISTING" >SDL_CD *cdrom; int cur_track; int min, sec, frame; SDL_Init(SDL_INIT_CDROM); atexit(SDL_Quit); /* Check for CD drives */ if(!SDL_CDNumDrives()){ /* None found */ fprintf(stderr, "No CDROM devices available\n"); exit(-1); } /* Open the default drive */ cdrom=SDL_CDOpen(0); /* Did if open? Check if cdrom is NULL */ if(!cdrom){ fprintf(stderr, "Couldn't open drive: %s\n", SDL_GetError()); exit(-1); } /* Print Volume info */ printf("Name: %s\n", SDL_CDName(0)); printf("Tracks: %d\n", cdrom->numtracks); for(cur_track=0;cur_track < cdrom->numtracks; cur_track++){ FRAMES_TO_MSF(cdrom->track[cur_track].length, &min, &sec, &frame); printf("\tTrack %d: Length %d:%d\n", cur_track, min, sec); } SDL_CDClose(cdrom);</PRE ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN7295" ></A ><H2 >See Also</H2 ><P ><A HREF="sdlcd.html" ><SPAN CLASS="STRUCTNAME" >SDL_CD</SPAN ></A >, <A HREF="sdlcdtrack.html" ><SPAN CLASS="STRUCTNAME" >SDL_CDtrack</SPAN ></A >, <A HREF="sdlcdclose.html" ><TT CLASS="FUNCTION" >SDL_CDClose</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="sdlcdname.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="sdlcdstatus.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >SDL_CDName</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="cdrom.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >SDL_CDStatus</TD ></TR ></TABLE ></DIV ></BODY ></HTML >