Use a non-default compiler list in AC_PROG_CC and AC_PROG_CXX, since autoconf/automake still doesn't know what Clang is.

config.h.in

@@ -1,6 +1,5 @@
 /* config.h.in.  Generated from configure.ac by autoheader.  */
 
-
 /* Define if building universal (internal helper macro) */
 #undef AC_APPLE_UNIVERSAL_BUILD
 

configure

@@ -3486,197 +3486,7 @@ ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
 ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
 ac_compiler_gnu=$ac_cv_c_compiler_gnu
 if test -n "$ac_tool_prefix"; then
-  # Extract the first word of "${ac_tool_prefix}gcc", so it can be a program name with args.
+  for ac_prog in gcc clang suncc aCC xlC_r xlC cl.exe
-set dummy ${ac_tool_prefix}gcc; ac_word=$2
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
-$as_echo_n "checking for $ac_word... " >&6; }
-if ${ac_cv_prog_CC+:} false; then :
-  $as_echo_n "(cached) " >&6
-else
-  if test -n "$CC"; then
-  ac_cv_prog_CC="$CC" # Let the user override the test.
-else
-as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
-for as_dir in $PATH
-do
-  IFS=$as_save_IFS
-  test -z "$as_dir" && as_dir=.
-    for ac_exec_ext in '' $ac_executable_extensions; do
-  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
-    ac_cv_prog_CC="${ac_tool_prefix}gcc"
-    $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
-    break 2
-  fi
-done
-  done
-IFS=$as_save_IFS
-
-fi
-fi
-CC=$ac_cv_prog_CC
-if test -n "$CC"; then
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $CC" >&5
-$as_echo "$CC" >&6; }
-else
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
-$as_echo "no" >&6; }
-fi
-
-
-fi
-if test -z "$ac_cv_prog_CC"; then
-  ac_ct_CC=$CC
-  # Extract the first word of "gcc", so it can be a program name with args.
-set dummy gcc; ac_word=$2
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
-$as_echo_n "checking for $ac_word... " >&6; }
-if ${ac_cv_prog_ac_ct_CC+:} false; then :
-  $as_echo_n "(cached) " >&6
-else
-  if test -n "$ac_ct_CC"; then
-  ac_cv_prog_ac_ct_CC="$ac_ct_CC" # Let the user override the test.
-else
-as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
-for as_dir in $PATH
-do
-  IFS=$as_save_IFS
-  test -z "$as_dir" && as_dir=.
-    for ac_exec_ext in '' $ac_executable_extensions; do
-  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
-    ac_cv_prog_ac_ct_CC="gcc"
-    $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
-    break 2
-  fi
-done
-  done
-IFS=$as_save_IFS
-
-fi
-fi
-ac_ct_CC=$ac_cv_prog_ac_ct_CC
-if test -n "$ac_ct_CC"; then
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_ct_CC" >&5
-$as_echo "$ac_ct_CC" >&6; }
-else
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
-$as_echo "no" >&6; }
-fi
-
-  if test "x$ac_ct_CC" = x; then
-    CC=""
-  else
-    case $cross_compiling:$ac_tool_warned in
-yes:)
-{ $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: using cross tools not prefixed with host triplet" >&5
-$as_echo "$as_me: WARNING: using cross tools not prefixed with host triplet" >&2;}
-ac_tool_warned=yes ;;
-esac
-    CC=$ac_ct_CC
-  fi
-else
-  CC="$ac_cv_prog_CC"
-fi
-
-if test -z "$CC"; then
-          if test -n "$ac_tool_prefix"; then
-    # Extract the first word of "${ac_tool_prefix}cc", so it can be a program name with args.
-set dummy ${ac_tool_prefix}cc; ac_word=$2
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
-$as_echo_n "checking for $ac_word... " >&6; }
-if ${ac_cv_prog_CC+:} false; then :
-  $as_echo_n "(cached) " >&6
-else
-  if test -n "$CC"; then
-  ac_cv_prog_CC="$CC" # Let the user override the test.
-else
-as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
-for as_dir in $PATH
-do
-  IFS=$as_save_IFS
-  test -z "$as_dir" && as_dir=.
-    for ac_exec_ext in '' $ac_executable_extensions; do
-  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
-    ac_cv_prog_CC="${ac_tool_prefix}cc"
-    $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
-    break 2
-  fi
-done
-  done
-IFS=$as_save_IFS
-
-fi
-fi
-CC=$ac_cv_prog_CC
-if test -n "$CC"; then
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $CC" >&5
-$as_echo "$CC" >&6; }
-else
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
-$as_echo "no" >&6; }
-fi
-
-
-  fi
-fi
-if test -z "$CC"; then
-  # Extract the first word of "cc", so it can be a program name with args.
-set dummy cc; ac_word=$2
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
-$as_echo_n "checking for $ac_word... " >&6; }
-if ${ac_cv_prog_CC+:} false; then :
-  $as_echo_n "(cached) " >&6
-else
-  if test -n "$CC"; then
-  ac_cv_prog_CC="$CC" # Let the user override the test.
-else
-  ac_prog_rejected=no
-as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
-for as_dir in $PATH
-do
-  IFS=$as_save_IFS
-  test -z "$as_dir" && as_dir=.
-    for ac_exec_ext in '' $ac_executable_extensions; do
-  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
-    if test "$as_dir/$ac_word$ac_exec_ext" = "/usr/ucb/cc"; then
-       ac_prog_rejected=yes
-       continue
-     fi
-    ac_cv_prog_CC="cc"
-    $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
-    break 2
-  fi
-done
-  done
-IFS=$as_save_IFS
-
-if test $ac_prog_rejected = yes; then
-  # We found a bogon in the path, so make sure we never use it.
-  set dummy $ac_cv_prog_CC
-  shift
-  if test $# != 0; then
-    # We chose a different compiler from the bogus one.
-    # However, it has the same basename, so the bogon will be chosen
-    # first if we set CC to just the basename; use the full file name.
-    shift
-    ac_cv_prog_CC="$as_dir/$ac_word${1+' '}$@"
-  fi
-fi
-fi
-fi
-CC=$ac_cv_prog_CC
-if test -n "$CC"; then
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $CC" >&5
-$as_echo "$CC" >&6; }
-else
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
-$as_echo "no" >&6; }
-fi
-
-
-fi
-if test -z "$CC"; then
-  if test -n "$ac_tool_prefix"; then
-  for ac_prog in cl.exe
   do
     # Extract the first word of "$ac_tool_prefix$ac_prog", so it can be a program name with args.
 set dummy $ac_tool_prefix$ac_prog; ac_word=$2
@@ -3720,7 +3530,7 @@ fi
 fi
 if test -z "$CC"; then
   ac_ct_CC=$CC
-  for ac_prog in cl.exe
+  for ac_prog in gcc clang suncc aCC xlC_r xlC cl.exe
 do
   # Extract the first word of "$ac_prog", so it can be a program name with args.
 set dummy $ac_prog; ac_word=$2
@@ -3775,8 +3585,6 @@ esac
   fi
 fi
 
-fi
-
 
 test -z "$CC" && { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
 $as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
@@ -4529,7 +4337,7 @@ if test -z "$CXX"; then
     CXX=$CCC
   else
     if test -n "$ac_tool_prefix"; then
-  for ac_prog in g++ c++ gpp aCC CC cxx cc++ cl.exe FCC KCC RCC xlC_r xlC
+  for ac_prog in g++ clang++ sunCC aCC xlC_r xlC cl.exe
   do
     # Extract the first word of "$ac_tool_prefix$ac_prog", so it can be a program name with args.
 set dummy $ac_tool_prefix$ac_prog; ac_word=$2
@@ -4573,7 +4381,7 @@ fi
 fi
 if test -z "$CXX"; then
   ac_ct_CXX=$CXX
-  for ac_prog in g++ c++ gpp aCC CC cxx cc++ cl.exe FCC KCC RCC xlC_r xlC
+  for ac_prog in g++ clang++ sunCC aCC xlC_r xlC cl.exe
 do
   # Extract the first word of "$ac_prog", so it can be a program name with args.
 set dummy $ac_prog; ac_word=$2

configure.ac

@@ -41,8 +41,8 @@ fi
 dnl ###################
 dnl Checks for programs
 dnl ###################
-AC_PROG_CC
+AC_PROG_CC([gcc clang suncc aCC xlC_r xlC cl.exe])
-AC_PROG_CXX
+AC_PROG_CXX([g++ clang++ sunCC aCC xlC_r xlC cl.exe])
 AC_PROG_RANLIB
 AC_PROG_YACC
 AC_PROG_LN_S