acinclude/ac_check_define.m4
author Sam Lantinga <slouken@libsdl.org>
Wed, 30 Nov 2016 22:06:05 -0800
changeset 10668 1889c850fafc
parent 6491 03b7e6b0a8bf
permissions -rw-r--r--
Fixed bug 3340 - SDL_BlitScaled causes access violation in some cases.

Simon Hug

The SDL_BlitScaled function runs into an access violation for specific blit coordinates and surface sizes. The attached testcase blits a 800x600 surface to a 1280x720 surface at the coordinates -640,-345 scaled to 1280x720. The blit function that moves the data then runs over and reads after the pixel data from the src surface causing an access violation.

I can't say where exactly it goes wrong, but I think it could have something to do with the rounding in SDL_UpperBlitScaled. final_src.y is 288 and final_src.h is 313. Together that's 601, which I believe is one too much, but I just don't know the code enough to make sure that's the problem.

Sylvain

I think this patch fix the issue, but maybe it's worth re-writing "SDL_UpperBlitScaled" using SDL_FRect.
     1 AC_DEFUN([AC_CHECK_DEFINE],[dnl
     2   AC_CACHE_CHECK(for $1 in $2, ac_cv_define_$1,
     3     AC_EGREP_CPP([YES_IS_DEFINED], [
     4 #include <$2>
     5 #ifdef $1
     6 YES_IS_DEFINED
     7 #endif
     8     ], ac_cv_define_$1=yes, ac_cv_define_$1=no)
     9   )
    10   if test "$ac_cv_define_$1" = "yes" ; then
    11     AC_DEFINE([HAVE_$1],[],[Added by AC_CHECK_DEFINE])
    12   fi
    13 ])dnl
    14 AC_DEFINE([HAVE_$1],[],[Added by AC_CHECK_DEFINE])