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.
slouken@6491
     1
AC_DEFUN([AC_CHECK_DEFINE],[dnl
slouken@3342
     2
  AC_CACHE_CHECK(for $1 in $2, ac_cv_define_$1,
slouken@3342
     3
    AC_EGREP_CPP([YES_IS_DEFINED], [
slouken@3342
     4
#include <$2>
slouken@3342
     5
#ifdef $1
slouken@3342
     6
YES_IS_DEFINED
slouken@3342
     7
#endif
slouken@3342
     8
    ], ac_cv_define_$1=yes, ac_cv_define_$1=no)
slouken@3342
     9
  )
slouken@3342
    10
  if test "$ac_cv_define_$1" = "yes" ; then
slouken@3374
    11
    AC_DEFINE([HAVE_$1],[],[Added by AC_CHECK_DEFINE])
slouken@3342
    12
  fi
slouken@3342
    13
])dnl
slouken@3374
    14
AC_DEFINE([HAVE_$1],[],[Added by AC_CHECK_DEFINE])