m4: Add missing as-compiler-flag.m4 macro

m4/as-compiler-flag.m4

@@ -0,0 +1,62 @@
+dnl as-compiler-flag.m4 0.1.0
+
+dnl autostars m4 macro for detection of compiler flags
+
+dnl David Schleef <[email protected]>
+
+dnl $Id: as-compiler-flag.m4,v 1.1 2005/12/15 23:35:19 ds Exp $
+
+dnl AS_COMPILER_FLAG(CFLAGS, ACTION-IF-ACCEPTED, [ACTION-IF-NOT-ACCEPTED])
+dnl Tries to compile with the given CFLAGS.
+dnl Runs ACTION-IF-ACCEPTED if the compiler can compile with the flags,
+dnl and ACTION-IF-NOT-ACCEPTED otherwise.
+
+AC_DEFUN([AS_COMPILER_FLAG],
+[
+  AC_MSG_CHECKING([to see if compiler understands $1])
+
+  save_CFLAGS="$CFLAGS"
+  CFLAGS="$CFLAGS $1"
+
+  AC_TRY_COMPILE([ ], [], [flag_ok=yes], [flag_ok=no])
+  CFLAGS="$save_CFLAGS"
+
+  if test "X$flag_ok" = Xyes ; then
+    m4_ifvaln([$2],[$2])
+    true
+  else
+    m4_ifvaln([$3],[$3])
+    true
+  fi
+  AC_MSG_RESULT([$flag_ok])
+])
+
+dnl AS_COMPILER_FLAGS(VAR, FLAGS)
+dnl Tries to compile with the given CFLAGS.
+
+AC_DEFUN([AS_COMPILER_FLAGS],
+[
+  list=$2
+  flags_supported=""
+  flags_unsupported=""
+  AC_MSG_CHECKING([for supported compiler flags])
+  for each in $list
+  do
+    save_CFLAGS="$CFLAGS"
+    CFLAGS="$CFLAGS $each"
+    AC_TRY_COMPILE([ ], [], [flag_ok=yes], [flag_ok=no])
+    CFLAGS="$save_CFLAGS"
+
+    if test "X$flag_ok" = Xyes ; then
+      flags_supported="$flags_supported $each"
+    else
+      flags_unsupported="$flags_unsupported $each"
+    fi
+  done
+  AC_MSG_RESULT([$flags_supported])
+  if test "X$flags_unsupported" != X ; then
+    AC_MSG_WARN([unsupported compiler flags: $flags_unsupported])
+  fi
+  $1="$$1 $flags_supported"
+])
+