annotate src/hermes/README @ 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 |
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74212992fb08 |
children |
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1 HERMES 1.2.4 (c)1998 Christian Nentwich (brn) (c.nentwich@cs.ucl.ac.uk)
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2 and quite a few assembler routines (c) Glenn Fielder (gaffer@gaffer.org)
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3
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4 This library and all the files enclosed in this package are free software
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5 under the terms of the GNU Library General Public License (LGPL). Please
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6 refer to the included file COPYING.LIB for the exact terms.
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7 ----------------------------------------------------------------------------
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8
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9 This is a stripped down version of HERMES, including only the x86 assembler
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10 converters, for use with Simple DirectMedia Layer.
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11
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12 The full HERMES library is available at: http://hermes.terminal.at/
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13
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