SDL_mixer: revert replace AM_PATH_SDL2 usage with corresponding PKG_CHECK_MODULES.

From 69f1cb0800aa333464b9fa81203453079f47b917 Mon Sep 17 00:00:00 2001
From: Ozkan Sezer <[EMAIL REDACTED]>
Date: Mon, 7 Nov 2022 21:15:40 +0300
Subject: [PATCH] revert replace AM_PATH_SDL2 usage with corresponding
 PKG_CHECK_MODULES.

Reference issue: https://github.com/libsdl-org/SDL/issues/6494 .
---
 acinclude/sdl2.m4 | 180 ++++++++++++++++++++++
 configure         | 373 ++++++++++++++++++++++++++++++++++++++++++----
 configure.ac      |   5 +-
 3 files changed, 525 insertions(+), 33 deletions(-)
 create mode 100644 acinclude/sdl2.m4

diff --git a/acinclude/sdl2.m4 b/acinclude/sdl2.m4
new file mode 100644
index 00000000..af101a84
--- /dev/null
+++ b/acinclude/sdl2.m4
@@ -0,0 +1,180 @@
+# Configure paths for SDL
+# Sam Lantinga 9/21/99
+# stolen from Manish Singh
+# stolen back from Frank Belew
+# stolen from Manish Singh
+# Shamelessly stolen from Owen Taylor
+
+# serial 2
+
+dnl AM_PATH_SDL2([MINIMUM-VERSION, [ACTION-IF-FOUND [, ACTION-IF-NOT-FOUND]]])
+dnl Test for SDL, and define SDL_CFLAGS and SDL_LIBS
+dnl
+AC_DEFUN([AM_PATH_SDL2],
+[dnl
+dnl Get the cflags and libraries from the sdl2-config script
+dnl
+AC_ARG_WITH(sdl-prefix,[  --with-sdl-prefix=PFX   Prefix where SDL is installed (optional)],
+            sdl_prefix="$withval", sdl_prefix="")
+AC_ARG_WITH(sdl-exec-prefix,[  --with-sdl-exec-prefix=PFX Exec prefix where SDL is installed (optional)],
+            sdl_exec_prefix="$withval", sdl_exec_prefix="")
+AC_ARG_ENABLE(sdltest, [  --disable-sdltest       Do not try to compile and run a test SDL program],
+		    , enable_sdltest=yes)
+
+  min_sdl_version=ifelse([$1], ,2.0.0,$1)
+
+  if test "x$sdl_prefix$sdl_exec_prefix" = x ; then
+    PKG_CHECK_MODULES([SDL], [sdl2 >= $min_sdl_version],
+           [sdl_pc=yes],
+           [sdl_pc=no])
+  else
+    sdl_pc=no
+    if test x$sdl_exec_prefix != x ; then
+      sdl_config_args="$sdl_config_args --exec-prefix=$sdl_exec_prefix"
+      if test x${SDL2_CONFIG+set} != xset ; then
+        SDL2_CONFIG=$sdl_exec_prefix/bin/sdl2-config
+      fi
+    fi
+    if test x$sdl_prefix != x ; then
+      sdl_config_args="$sdl_config_args --prefix=$sdl_prefix"
+      if test x${SDL2_CONFIG+set} != xset ; then
+        SDL2_CONFIG=$sdl_prefix/bin/sdl2-config
+      fi
+    fi
+  fi
+
+  if test "x$sdl_pc" = xyes ; then
+    no_sdl=""
+    SDL2_CONFIG="pkg-config sdl2"
+  else
+    as_save_PATH="$PATH"
+    if test "x$prefix" != xNONE && test "$cross_compiling" != yes; then
+      PATH="$prefix/bin:$prefix/usr/bin:$PATH"
+    fi
+    AC_PATH_PROG(SDL2_CONFIG, sdl2-config, no, [$PATH])
+    PATH="$as_save_PATH"
+    AC_MSG_CHECKING(for SDL - version >= $min_sdl_version)
+    no_sdl=""
+
+    if test "$SDL2_CONFIG" = "no" ; then
+      no_sdl=yes
+    else
+      SDL_CFLAGS=`$SDL2_CONFIG $sdl_config_args --cflags`
+      SDL_LIBS=`$SDL2_CONFIG $sdl_config_args --libs`
+
+      sdl_major_version=`$SDL2_CONFIG $sdl_config_args --version | \
+             sed 's/\([[0-9]]*\).\([[0-9]]*\).\([[0-9]]*\)/\1/'`
+      sdl_minor_version=`$SDL2_CONFIG $sdl_config_args --version | \
+             sed 's/\([[0-9]]*\).\([[0-9]]*\).\([[0-9]]*\)/\2/'`
+      sdl_micro_version=`$SDL2_CONFIG $sdl_config_args --version | \
+             sed 's/\([[0-9]]*\).\([[0-9]]*\).\([[0-9]]*\)/\3/'`
+      if test "x$enable_sdltest" = "xyes" ; then
+        ac_save_CFLAGS="$CFLAGS"
+        ac_save_CXXFLAGS="$CXXFLAGS"
+        ac_save_LIBS="$LIBS"
+        CFLAGS="$CFLAGS $SDL_CFLAGS"
+        CXXFLAGS="$CXXFLAGS $SDL_CFLAGS"
+        LIBS="$LIBS $SDL_LIBS"
+dnl
+dnl Now check if the installed SDL is sufficiently new. (Also sanity
+dnl checks the results of sdl2-config to some extent
+dnl
+      rm -f conf.sdltest
+      AC_RUN_IFELSE([AC_LANG_SOURCE([[
+#include <stdio.h>
+#include <stdlib.h>
+#include "SDL.h"
+
+int main (int argc, char *argv[])
+{
+  int major, minor, micro;
+  FILE *fp = fopen("conf.sdltest", "w");
+
+  if (fp) fclose(fp);
+
+  if (sscanf("$min_sdl_version", "%d.%d.%d", &major, &minor, &micro) != 3) {
+     printf("%s, bad version string\n", "$min_sdl_version");
+     exit(1);
+   }
+
+   if (($sdl_major_version > major) ||
+      (($sdl_major_version == major) && ($sdl_minor_version > minor)) ||
+      (($sdl_major_version == major) && ($sdl_minor_version == minor) && ($sdl_micro_version >= micro)))
+    {
+      return 0;
+    }
+  else
+    {
+      printf("\n*** 'sdl2-config --version' returned %d.%d.%d, but the minimum version\n", $sdl_major_version, $sdl_minor_version, $sdl_micro_version);
+      printf("*** of SDL required is %d.%d.%d. If sdl2-config is correct, then it is\n", major, minor, micro);
+      printf("*** best to upgrade to the required version.\n");
+      printf("*** If sdl2-config was wrong, set the environment variable SDL2_CONFIG\n");
+      printf("*** to point to the correct copy of sdl2-config, and remove the file\n");
+      printf("*** config.cache before re-running configure\n");
+      return 1;
+    }
+}
+
+]])], [], [no_sdl=yes], [echo $ac_n "cross compiling; assumed OK... $ac_c"])
+        CFLAGS="$ac_save_CFLAGS"
+        CXXFLAGS="$ac_save_CXXFLAGS"
+        LIBS="$ac_save_LIBS"
+      fi
+    fi
+    if test "x$no_sdl" = x ; then
+      AC_MSG_RESULT(yes)
+    else
+      AC_MSG_RESULT(no)
+    fi
+  fi
+  if test "x$no_sdl" = x ; then
+     ifelse([$2], , :, [$2])
+  else
+     if test "$SDL2_CONFIG" = "no" ; then
+       echo "*** The sdl2-config script installed by SDL could not be found"
+       echo "*** If SDL was installed in PREFIX, make sure PREFIX/bin is in"
+       echo "*** your path, or set the SDL2_CONFIG environment variable to the"
+       echo "*** full path to sdl2-config."
+     else
+       if test -f conf.sdltest ; then
+        :
+       else
+          echo "*** Could not run SDL test program, checking why..."
+          CFLAGS="$CFLAGS $SDL_CFLAGS"
+          CXXFLAGS="$CXXFLAGS $SDL_CFLAGS"
+          LIBS="$LIBS $SDL_LIBS"
+          AC_LINK_IFELSE([AC_LANG_PROGRAM([[
+#include <stdio.h>
+#include "SDL.h"
+
+int main(int argc, char *argv[])
+{ return 0; }
+#undef  main
+#define main K_and_R_C_main
+]], [[ return 0; ]])],
+        [ echo "*** The test program compiled, but did not run. This usually means"
+          echo "*** that the run-time linker is not finding SDL or finding the wrong"
+          echo "*** version of SDL. If it is not finding SDL, you'll need to set your"
+          echo "*** LD_LIBRARY_PATH environment variable, or edit /etc/ld.so.conf to point"
+          echo "*** to the installed location  Also, make sure you have run ldconfig if that"
+          echo "*** is required on your system"
+	  echo "***"
+          echo "*** If you have an old version installed, it is best to remove it, although"
+          echo "*** you may also be able to get things to work by modifying LD_LIBRARY_PATH"],
+        [ echo "*** The test program failed to compile or link. See the file config.log for the"
+          echo "*** exact error that occured. This usually means SDL was incorrectly installed"
+          echo "*** or that you have moved SDL since it was installed. In the latter case, you"
+          echo "*** may want to edit the sdl2-config script: $SDL2_CONFIG" ])
+          CFLAGS="$ac_save_CFLAGS"
+          CXXFLAGS="$ac_save_CXXFLAGS"
+          LIBS="$ac_save_LIBS"
+       fi
+     fi
+     SDL_CFLAGS=""
+     SDL_LIBS=""
+     ifelse([$3], , :, [$3])
+  fi
+  AC_SUBST(SDL_CFLAGS)
+  AC_SUBST(SDL_LIBS)
+  rm -f conf.sdltest
+])
diff --git a/configure b/configure
index 52fdca6a..b6bfa015 100755
--- a/configure
+++ b/configure
@@ -847,6 +847,7 @@ XMP_LIBS
 XMP_CFLAGS
 MODPLUG_LIBS
 MODPLUG_CFLAGS
+SDL2_CONFIG
 SDL_LIBS
 SDL_CFLAGS
 SORT
@@ -960,6 +961,9 @@ enable_fast_install
 with_gnu_ld
 enable_libtool_lock
 enable_dependency_tracking
+with_sdl_prefix
+with_sdl_exec_prefix
+enable_sdltest
 enable_music_cmd
 enable_music_wave
 enable_music_mod
@@ -1653,6 +1657,7 @@ Optional Features:
   --disable-libtool-lock  avoid locking (might break parallel builds)
   --enable-dependency-tracking
                           Use gcc -MMD -MT dependency tracking [default=yes]
+  --disable-sdltest       Do not try to compile and run a test SDL program
   --enable-music-cmd      support an external music player [default=yes]
   --enable-music-wave     enable streaming WAVE music [default=yes]
   --enable-music-mod      enable MOD music [default=yes]
@@ -1708,6 +1713,8 @@ Optional Packages:
   --with-pic              try to use only PIC/non-PIC objects [default=use
                           both]
   --with-gnu-ld           assume the C compiler uses GNU ld [default=no]
+  --with-sdl-prefix=PFX   Prefix where SDL is installed (optional)
+  --with-sdl-exec-prefix=PFX Exec prefix where SDL is installed (optional)
   --with-timidity-cfg=FILE
                           Specify full path to timidity.cfg
 
@@ -2140,6 +2147,49 @@ fi
   as_fn_set_status $ac_retval
 
 } # ac_fn_cxx_try_link
+
+# ac_fn_c_try_run LINENO
+# ----------------------
+# Try to run conftest.$ac_ext, and return whether this succeeded. Assumes that
+# executables *can* be run.
+ac_fn_c_try_run ()
+{
+  as_lineno=${as_lineno-"$1"} as_lineno_stack=as_lineno_stack=$as_lineno_stack
+  if { { ac_try="$ac_link"
+case "(($ac_try" in
+  *\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
+  *) ac_try_echo=$ac_try;;
+esac
+eval ac_try_echo="\"\$as_me:${as_lineno-$LINENO}: $ac_try_echo\""
+printf "%s\n" "$ac_try_echo"; } >&5
+  (eval "$ac_link") 2>&5
+  ac_status=$?
+  printf "%s\n" "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; } && { ac_try='./conftest$ac_exeext'
+  { { case "(($ac_try" in
+  *\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
+  *) ac_try_echo=$ac_try;;
+esac
+eval ac_try_echo="\"\$as_me:${as_lineno-$LINENO}: $ac_try_echo\""
+printf "%s\n" "$ac_try_echo"; } >&5
+  (eval "$ac_try") 2>&5
+  ac_status=$?
+  printf "%s\n" "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; }
+then :
+  ac_retval=0
+else $as_nop
+  printf "%s\n" "$as_me: program exited with status $ac_status" >&5
+       printf "%s\n" "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+       ac_retval=$ac_status
+fi
+  rm -rf conftest.dSYM conftest_ipa8_conftest.oo
+  eval $as_lineno_stack; ${as_lineno_stack:+:} unset as_lineno
+  as_fn_set_status $ac_retval
+
+} # ac_fn_c_try_run
 ac_configure_args_raw=
 for ac_arg
 do
@@ -4886,13 +4936,13 @@ then :
 else $as_nop
   lt_cv_nm_interface="BSD nm"
   echo "int some_variable = 0;" > conftest.$ac_ext
-  (eval echo "\"\$as_me:4889: $ac_compile\"" >&5)
+  (eval echo "\"\$as_me:4939: $ac_compile\"" >&5)
   (eval "$ac_compile" 2>conftest.err)
   cat conftest.err >&5
-  (eval echo "\"\$as_me:4892: $NM \\\"conftest.$ac_objext\\\"\"" >&5)
+  (eval echo "\"\$as_me:4942: $NM \\\"conftest.$ac_objext\\\"\"" >&5)
   (eval "$NM \"conftest.$ac_objext\"" 2>conftest.err > conftest.out)
   cat conftest.err >&5
-  (eval echo "\"\$as_me:4895: output\"" >&5)
+  (eval echo "\"\$as_me:4945: output\"" >&5)
   cat conftest.out >&5
   if $GREP 'External.*some_variable' conftest.out > /dev/null; then
     lt_cv_nm_interface="MS dumpbin"
@@ -6151,7 +6201,7 @@ ia64-*-hpux*)
   ;;
 *-*-irix6*)
   # Find out which ABI we are using.
-  echo '#line 6154 "configure"' > conftest.$ac_ext
+  echo '#line 6204 "configure"' > conftest.$ac_ext
   if { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_compile\""; } >&5
   (eval $ac_compile) 2>&5
   ac_status=$?
@@ -7824,11 +7874,11 @@ else $as_nop
    -e 's:.*FLAGS}\{0,1\} :&$lt_compiler_flag :; t' \
    -e 's: [^ ]*conftest\.: $lt_compiler_flag&:; t' \
    -e 's:$: $lt_compiler_flag:'`
-   (eval echo "\"\$as_me:7827: $lt_compile\"" >&5)
+   (eval echo "\"\$as_me:7877: $lt_compile\"" >&5)
    (eval "$lt_compile" 2>conftest.err)
    ac_status=$?
    cat conftest.err >&5
-   echo "$as_me:7831: \$? = $ac_status" >&5
+   echo "$as_me:7881: \$? = $ac_status" >&5
    if (exit $ac_status) && test -s "$ac_outfile"; then
      # The compiler can only warn and ignore the option if not recognized
      # So say no if there are warnings other than the usual output.
@@ -8174,11 +8224,11 @@ else $as_nop
    -e 's:.*FLAGS}\{0,1\} :&$lt_compiler_flag :; t' \
    -e 's: [^ ]*conftest\.: $lt_compiler_flag&:; t' \
    -e 's:$: $lt_compiler_flag:'`
-   (eval echo "\"\$as_me:8177: $lt_compile\"" >&5)
+   (eval echo "\"\$as_me:8227: $lt_compile\"" >&5)
    (eval "$lt_compile" 2>conftest.err)
    ac_status=$?
    cat conftest.err >&5
-   echo "$as_me:8181: \$? = $ac_status" >&5
+   echo "$as_me:8231: \$? = $ac_status" >&5
    if (exit $ac_status) && test -s "$ac_outfile"; then
      # The compiler can only warn and ignore the option if not recognized
      # So say no if there are warnings other than the usual output.
@@ -8281,11 +8331,11 @@ else $as_nop
    -e 's:.*FLAGS}\{0,1\} :&$lt_compiler_flag :; t' \
    -e 's: [^ ]*conftest\.: $lt_compiler_flag&:; t' \
    -e 's:$: $lt_compiler_flag:'`
-   (eval echo "\"\$as_me:8284: $lt_compile\"" >&5)
+   (eval echo "\"\$as_me:8334: $lt_compile\"" >&5)
    (eval "$lt_compile" 2>out/conftest.err)
    ac_status=$?
    cat out/conftest.err >&5
-   echo "$as_me:8288: \$? = $ac_status" >&5
+   echo "$as_me:8338: \$? = $ac_status" >&5
    if (exit $ac_status) && test -s out/conftest2.$ac_objext
    then
      # The compiler can only warn and ignore the option if not recognized
@@ -8337,11 +8387,11 @@ else $as_nop
    -e 's:.*FLAGS}\{0,1\} :&$lt_compiler_flag :; t' \
    -e 's: [^ ]*conftest\.: $lt_compiler_flag&:; t' \
    -e 's:$: $lt_compiler_flag:'`
-   (eval echo "\"\$as_me:8340: $lt_compile\"" >&5)
+   (eval echo "\"\$as_me:8390: $lt_compile\"" >&5)
    (eval "$lt_compile" 2>out/conftest.err)
    ac_status=$?
    cat out/conftest.err >&5
-   echo "$as_me:8344: \$? = $ac_status" >&5
+   echo "$as_me:8394: \$? = $ac_status" >&5
    if (exit $ac_status) && test -s out/conftest2.$ac_objext
    then
      # The compiler can only warn and ignore the option if not recognized
@@ -10780,7 +10830,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 10783 "configure"
+#line 10833 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -10877,7 +10927,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 10880 "configure"
+#line 10930 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -14576,11 +14626,11 @@ else $as_nop
    -e 's:.*FLAGS}\{0,1\} :&$lt_compiler_flag :; t' \
    -e 's: [^ ]*conftest\.: $lt_compiler_flag&:; t' \
    -e 's:$: $lt_compiler_flag:'`
-   (eval echo "\"\$as_me:14579: $lt_compile\"" >&5)
+   (eval echo "\"\$as_me:14629: $lt_compile\"" >&5)
    (eval "$lt_compile" 2>conftest.err)
    ac_status=$?
    cat conftest.err >&5
-   echo "$as_me:14583: \$? = $ac_status" >&5
+   echo "$as_me:14633: \$? = $ac_status" >&5
    if (exit $ac_status) && test -s "$ac_outfile"; then
      # The compiler can only warn and ignore the option if not recognized
      # So say no if there are warnings other than the usual output.
@@ -14677,11 +14727,11 @@ else $as_nop
    -e 's:.*FLAGS}\{0,1\} :&$lt_compiler_flag :; t' \
    -e 's: [^ ]*conftest\.: $lt_compiler_flag&:; t' \
    -e 's:$: $lt_compiler_flag:'`
-   (eval echo "\"\$as_me:14680: $lt_compile\"" >&5)
+   (eval echo "\"\$as_me:14730: $lt_compile\"" >&5)
    (eval "$lt_compile" 2>out/conftest.err)
    ac_status=$?
    cat out/conftest.err >&5
-   echo "$as_me:14684: \$? = $ac_status" >&5
+   echo "$as_me:14734: \$? = $ac_status" >&5
    if (exit $ac_status) && test -s out/conftest2.$ac_objext
    then
      # The compiler can only warn and ignore the option if not recognized
@@ -14730,11 +14780,11 @@ else $as_nop
    -e 's:.*FLAGS}\{0,1\} :&$lt_compiler_flag :; t' \
    -e 's: [^ ]*conftest\.: $lt_compiler_flag&:; t' \
    -e 's:$: $lt_compiler_flag:'`
-   (eval echo "\"\$as_me:14733: $lt_compile\"" >&5)
+   (eval echo "\"\$as_me:14783: $lt_compile\"" >&5)
    (eval "$lt_compile" 2>out/conftest.err)
    ac_status=$?
    cat out/conftest.err >&5
-   echo "$as_me:14737: \$? = $ac_status" >&5
+   echo "$as_me:14787: \$? = $ac_status" >&5
    if (exit $ac_status) && test -s out/conftest2.$ac_objext
    then
      # The compiler can only warn and ignore the option if not recognized
@@ -16475,20 +16525,50 @@ find_lib()
 
 SDL_VERSION=2.0.9
 
+# Check whether --with-sdl-prefix was given.
+if test ${with_sdl_prefix+y}
+then :
+  withval=$with_sdl_prefix; sdl_prefix="$withval"
+else $as_nop
+  sdl_prefix=""
+fi
+
+
+# Check whether --with-sdl-exec-prefix was given.
+if test ${with_sdl_exec_prefix+y}
+then :
+  withval=$with_sdl_exec_prefix; sdl_exec_prefix="$withval"
+else $as_nop
+  sdl_exec_prefix=""
+fi
+
+# Check whether --enable-sdltest was given.
+if test ${enable_sdltest+y}
+then :
+  enableval=$enable_sdltest;
+else $as_nop
+  enable_sdltest=yes
+fi
+
+
+  min_sdl_version=$SDL_VERSION
+
+  if test "x$sdl_prefix$sdl_exec_prefix" = x ; then
+
 pkg_failed=no
-{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for sdl2 >= $SDL_VERSION" >&5
-printf %s "checking for sdl2 >= $SDL_VERSION... " >&6; }
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for sdl2 >= $min_sdl_version" >&5
+printf %s "checking for sdl2 >= $min_sdl_version... " >&6; }
 
 if test -n "$SDL_CFLAGS"; then
     pkg_cv_SDL_CFLAGS="$SDL_CFLAGS"
  elif test -n "$PKG_CONFIG"; then
     if test -n "$PKG_CONFIG" && \
-    { { printf "%s\n" "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"sdl2 >= \$SDL_VERSION\""; } >&5
-  ($PKG_CONFIG --exists --print-errors "sdl2 >= $SDL_VERSION") 2>&5
+    { { printf "%s\n" "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"sdl2 >= \$min_sdl_version\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "sdl2 >= $min_sdl_version") 2>&5
   ac_status=$?
   printf "%s\n" "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
   test $ac_status = 0; }; then
-  pkg_cv_SDL_CFLAGS=`$PKG_CONFIG --cflags "sdl2 >= $SDL_VERSION" 2>/dev/null`
+  pkg_cv_SDL_CFLAGS=`$PKG_CONFIG --cflags "sdl2 >= $min_sdl_version" 2>/dev/null`
 		      test "x$?" != "x0" && pkg_failed=yes
 else
   pkg_failed=yes
@@ -16500,12 +16580,12 @@ if test -n "$SDL_LIBS"; then
     pkg_cv_SDL_LIBS="$SDL_LIBS"
  elif test -n "$PKG_CONFIG"; then
     if test -n "$PKG_CONFIG" && \
-    { { printf "%s\n" "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"sdl2 >= \$SDL_VERSION\""; } >&5
-  ($PKG_CONFIG --exists --print-errors "sdl2 >= $SDL_VERSION") 2>&5
+    { { printf "%s\n" "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"sdl2 >= \$min_sdl_version\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "sdl2 >= $min_sdl_version") 2>&5
   ac_status=$?
   printf "%s\n" "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
   test $ac_status = 0; }; then
-  pkg_cv_SDL_LIBS=`$PKG_CONFIG --libs "sdl2 >= $SDL_VERSION" 2>/dev/null`
+  pkg_cv_SDL_LIBS=`$PKG_CONFIG --libs "sdl2 >= $min_sdl_version" 2>/dev/null`
 		      test "x$?" != "x0" && pkg_failed=yes
 else
   pkg_failed=yes
@@ -16526,25 +16606,254 @@ else
         _pkg_short_errors_supported=no
 fi
         if test $_pkg_short_errors_supported = yes; then
-	        SDL_PKG_ERRORS=`$PKG_CONFIG --short-errors --print-errors --cflags --libs "sdl2 >= $SDL_VERSION" 2>&1`
+	        SDL_PKG_ERRORS=`$PKG_CONFIG --short-errors --print-errors --cflags --libs "sdl2 >= $min_sdl_version" 2>&1`
         else
-	        SDL_PKG_ERRORS=`$PKG_CONFIG --print-errors --cflags --libs "sdl2 >= $SDL_VERSION" 2>&1`
+	        SDL_PKG_ERRORS=`$PKG_CONFIG --print-errors --cflags --libs "sdl2 >= $min_sdl_version" 2>&1`
         fi
 	# Put the nasty error message in config.log where it belongs
 	echo "$SDL_PKG_ERRORS" >&5
 
-	as_fn_error $? "*** SDL version $SDL_VERSION not found!" "$LINENO" 5
+	sdl_pc=no
 elif test $pkg_failed = untried; then
         { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: no" >&5
 printf "%s\n" "no" >&6; }
-	as_fn_error $? "*** SDL version $SDL_VERSION not found!" "$LINENO" 5
+	sdl_pc=no
 else
 	SDL_CFLAGS=$pkg_cv_SDL_CFLAGS
 	SDL_LIBS=$pkg_cv_SDL_LIBS
         { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: yes" >&5
 printf "%s\n" "yes" >&6; }
+	sdl_pc=yes
+fi
+  else
+    sdl_pc=no
+    if test x$sdl_exec_prefix != x ; then
+      sdl_config_args="$sdl_config_args --exec-prefix=$sdl_exec_prefix"
+      if test x${SDL2_CONFIG+set} != xset ; then
+        SDL2_CONFIG=$sdl_exec_prefix/bin/sdl2-config
+      fi
+    fi
+    if test x$sdl_prefix != x ; then
+      sdl_config_args="$sdl_config_args --prefix=$sdl_prefix"
+      if test x${SDL2_CONFIG+set} != xset ; then
+        SDL2_CONFIG=$sdl_prefix/bin/sdl2-config
+      fi
+    fi
+  fi
+
+  if test "x$sdl_pc" = xyes ; then
+    no_sdl=""
+    SDL2_CONFIG="pkg-config sdl2"
+  else
+    as_save_PATH="$PATH"
+    if test "x$prefix" != xNONE && test "$cross_compiling" != yes; then
+      PATH="$prefix/bin:$prefix/usr/bin:$PATH"
+    fi
+    # Extract the first word of "sdl2-config", so it can be a program name with args.
+set dummy sdl2-config; ac_word=$2
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
+printf %s "checking for $ac_word... " >&6; }
+if test ${ac_cv_path_SDL2_CONFIG+y}
+then :
+  printf %s "(cached) " >&6
+else $as_nop
+  case $SDL2_CONFIG in
+  [\\/]* | ?:[\\/]*)
+  ac_cv_path_SDL2_CONFIG="$SDL2_CONFIG" # Let the user override the test with a path.
+  ;;
+  *)
+  as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+for as_dir in $PATH
+do
+  IFS=$as_save_IFS
+  case $as_dir in #(((
+    '') as_dir=./ ;;
+    */) ;;
+    *) as_dir=$as_dir/ ;;
+  esac
+    for ac_exec_ext in '' $ac_executable_extensions; do
+  if as_fn_executable_p "$as_dir$ac_word$ac_exec_ext"; then
+    ac_cv_path_SDL2_CONFIG="$as_dir$ac_word$ac_exec_ext"
+    printf "%s\n" "$as_me:${as_lineno-$LINENO}: found $as_dir$ac_word$ac_exec_ext" >&5
+    break 2
+  fi
+done
+  done
+IFS=$as_save_IFS
+
+  test -z "$ac_cv_path_SDL2_CONFIG" && ac_cv_path_SDL2_CONFIG="no"
+  ;;
+esac
+fi
+SDL2_CONFIG=$ac_cv_path_SDL2_CONFIG
+if test -n "$SDL2_CONFIG"; then
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $SDL2_CONFIG" >&5
+printf "%s\n" "$SDL2_CONFIG" >&6; }
+else
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: no" >&5
+printf "%s\n" "no" >&6; }
+fi
+
+
+    PATH="$as_save_PATH"
+    { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for SDL - version >= $min_sdl_version" >&5
+printf %s "checking for SDL - version >= $min_sdl_version... " >&6; }
+    no_sdl=""
+
+    if test "$SDL2_CONFIG" = "no" ; then
+      no_sdl=yes
+    else
+      SDL_CFLAGS=`$SDL2_CONFIG $sdl_config_args --cflags`
+      SDL_LIBS=`$SDL2_CONFIG $sdl_config_args --libs`
+
+      sdl_major_version=`$SDL2_CONFIG $sdl_config_args --version | \
+             sed 's/\([0-9]*\).\([0-9]*\).\([0-9]*\)/\1/'`
+      sdl_minor_version=`$SDL2_CONFIG $sdl_config_args --version | \
+             sed 's/\([0-9]*\).\([0-9]*\).\([0-9]*\)/\2/'`
+      sdl_micro_version=`$SDL2_CONFIG $sdl_config_args --version | \
+             sed 's/\([0-9]*\).\([0-9]*\).\([0-9]*\)/\3/'`
+      if test "x$enable_sdltest" = "xyes" ; then
+        ac_save_CFLAGS="$CFLAGS"
+        ac_save_CXXFLAGS="$CXXFLAGS"
+        ac_save_LIBS="$LIBS"
+        CFLAGS="$CFLAGS $SDL_CFLAGS"
+        CXXFLAGS="$CXXFLAGS $SDL_CFLAGS"
+        LIBS="$LIBS $SDL_LIBS"
+      rm -f conf.sdltest
+      if test "$cross_compiling" = yes
+then :
+  echo $ac_n "cross compiling; assumed OK... $ac_c"
+else $as_nop
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include "SDL.h"
+
+int main (int argc, char *argv[])
+{
+  int major, minor, micro;
+  FILE *fp = fopen("conf.sdltest", "w");
+
+  if (fp) fclose(fp);
+
+  if (sscanf("$min_sdl_version", "%d.%d.%d", &major, &minor, &micro) != 3) {
+     printf("%s, bad version string\n", "$min_sdl_version");
+     exit(1);
+   }
+
+   if (($sdl_major_version > major) ||
+      (($sdl_major_version == major) && ($sdl_minor_version > minor)) ||
+      (($sdl_major_version == major) && ($sdl_minor_version == minor) && ($sdl_micro_version >= micro)))
+    {
+      return 0;
+    }
+  else
+    {
+      printf("\n*** 'sdl2-config --version' returned %d.%d.%d, but the minimum version\n", $sdl_major_version, $sdl_minor_version, $sdl_micro_version);
+      printf("*** of SDL required is %d.%d.%d. If sdl2-config is correct, then it is\n", major, minor, micro);
+      printf("*** best to upgrade to the required version.\n");
+      printf("*** If sdl2-config was wrong, set the environment variable SDL2_CONFIG\n");
+      printf("*** to point to the correct copy of sdl2-config, and remove the file\n");
+      printf("*** config.cache before re-running configure\n");
+      return 1;
+    }
+}
+
+
+_ACEOF
+if ac_fn_c_try_run "$LINENO"
+then :
+
+else $as_nop
+  no_sdl=yes
+fi
+rm -f core *.core core.conftest.* gmon.out bb.out conftest$ac_exeext \
+  conftest.$ac_objext conftest.beam conftest.$ac_ext
+fi
+
+        CFLAGS="$ac_save_CFLAGS"
+        CXXFLAGS="$ac_save_CXXFLAGS"
+        LIBS="$ac_save_LIBS"
+      fi
+    fi
+    if test "x$no_sdl" = x ; then
+      { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+printf "%s\n" "yes" >&6; }
+    else
+      { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: no" >&5
+printf "%s\n" "no" >&6; }
+    fi
+  fi
+  if test "x$no_sdl" = x ; then
+     :
+  else
+     if test "$SDL2_CONFIG" = "no" ; then
+       echo "*** The sdl2-config script installed by SDL could not be found"
+       echo "*** If SDL was installed in PREFIX, make sure PREFIX/bin is in"
+       echo "*** your path, or set the SDL2_CONFIG environment variable to the"
+       echo "*** full path to sdl2-config."
+     else
+       if test -f conf.sdltest ; then
+        :
+       else
+          echo "*** Could not run SDL test program, checking why..."
+          CFLAGS="$CFLAGS $SDL_CFLAGS"
+          CXXFLAGS="$CXXFLAGS $SDL_CFLAGS"
+          LIBS="$LIBS $SDL_LIBS"
+          cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+#include <stdio.h>
+#include "SDL.h"
 
+int main(int argc, char *argv[])
+{ return 0; }
+#undef  main
+#define main K_and_R_C_main
+
+int
+main (void)
+{
+ return 0;
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"
+then :
+   echo "*** The test program compiled, but did not run. This usually means"
+          echo "*** that the run-time linker is not finding SDL or finding the wrong"
+          echo "*** version of SDL. If it is not finding SDL, you'll need to set your"
+          echo "*** LD_LIBRARY_PATH environment variable, or edit /etc/ld.so.conf to point"
+          echo "*** to the installed location  Also, make sure you have run ldconfig if that"
+          echo "*** is required on your system"
+	  echo "***"
+          echo "*** If you have an old version installed, it is best to remove it, although"
+          echo "*** you may also be able to get things to work by modifying LD_LIBRARY_PATH"
+else $as_nop
+   echo "*** The test program failed to compile or link. See the file config.log for the"
+          echo "*** exact error that occured. This usually means SDL was incorrectly installed"
+          echo "*** or that you have moved SDL since it was installed. In the latter case, you"
+          echo "*** may want to edit the sdl2-config script: $SDL2_CONFIG"
 fi
+rm -f core conftest.err conftest.$ac_objext conftest.beam \
+    conftest$ac_exeext conftest.$ac_ext
+          CFLAGS="$ac_save_CFLAGS"
+          CXXFLAGS="$ac_save_CXXFLAGS"
+          LIBS="$ac_save_LIBS"
+       fi
+     fi
+     SDL_CFLAGS=""
+     SDL_LIBS=""
+     as_fn_error $? "*** SDL version $SDL_VERSION not found!" "$LINENO" 5
+
+  fi
+
+
+  rm -f conf.sdltest
+
 EXTRA_CFLAGS="$EXTRA_CFLAGS $SDL_CFLAGS"
 
 EXTRA_CFLAGS="$EXTRA_CFLAGS -DSDL_BUILD_MAJOR_VERSION=$MAJOR_VERSION -DSDL_BUILD_MINOR_VERSION=$MINOR_VERSION -DSDL_BUILD_MICRO_VERSION=$MICRO_VERSION"
diff --git a/configure.ac b/configure.ac
index 26f965b1..0a53897f 100644
--- a/configure.ac
+++ b/configure.ac
@@ -281,7 +281,10 @@ find_lib()
 
 dnl Check for SDL
 SDL_VERSION=2.0.9
-PKG_CHECK_MODULES([SDL], [sdl2 >= $SDL_VERSION],, AC_MSG_ERROR([*** SDL version $SDL_VERSION not found!]))
+AM_PATH_SDL2($SDL_VERSION,
+            :,
+            AC_MSG_ERROR([*** SDL version $SDL_VERSION not found!])
+)
 EXTRA_CFLAGS="$EXTRA_CFLAGS $SDL_CFLAGS"
 
 dnl For use in static assertions