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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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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12 The full HERMES library is available at: http://hermes.terminal.at/
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