Use autoconf to detect WORDS_LITTLEENDIAN

Use autoconf to detect littleendian word order, and use
WORDS_LITTLEENDIAN instead of X86_MEMORY when we don't require
unaligned memory accesses to be permitted.

compiler.h

@@ -103,6 +103,9 @@ char *strsep(char **, const char *);
  */
 #if defined(__386__) || defined(__i386__) || defined(__x86_64__)
 # define X86_MEMORY 1
+# ifndef WORDS_LITTLEENDIAN
+#  define WORDS_LITTLEENDIAN 1
+# endif
 #else
 # define X86_MEMORY 0
 #endif

configure.in

@@ -1,6 +1,6 @@
-dnl Process this file with autoconf 2.59 or later to produce
+dnl Process this file with autoconf 2.61 or later to produce
 dnl a configure script.
-AC_PREREQ(2.59)
+AC_PREREQ(2.61)
 AC_INIT(config.h.in)
 AC_CONFIG_HEADERS(config.h)
 
@@ -48,9 +48,7 @@ AC_PREFIX_PROGRAM(nasm)
 
 dnl Checks for programs.
 dnl Consider AC_USE_SYSTEM_EXTENSIONS if autoconf 2.61 is OK in the future
-AC_GNU_SOURCE
-AC_ISC_POSIX
-AC_MINIX
+AC_USE_SYSTEM_EXTENSIONS
 AC_PROG_CC
 AC_PROG_LN_S
 AC_PROG_MAKE_SET
@@ -95,6 +93,13 @@ AC_CHECK_HEADERS(stdbool.h)
 dnl Checks for typedefs, structures, and compiler characteristics.
 AC_C_CONST
 AC_TYPE_SIZE_T
+AC_C_BIGENDIAN(AC_DEFINE(WORDS_BIGENDIAN),AC_DEFINE(WORDS_LITTLEENDIAN))
+AH_TEMPLATE(WORDS_BIGENDIAN,
+[Define to 1 if your processor stores words with the most significant
+byte first (like Motorola and SPARC, unlike Intel and VAX).])
+AH_TEMPLATE(WORDS_LITTLEENDIAN,
+[Define to 1 if your processor stores words with the most significant
+byte first (like Intel and VAX, unlike Motorola and SPARC).])
 
 dnl Checks for library functions.
 AC_SUBST(XOBJS)

wsaa.h

@@ -4,10 +4,7 @@
 #include "compiler.h"
 #include "nasmlib.h"
 
-/* XXX: only LITTLE_ENDIAN is actually needed here.  The way these
-   macros is written, it does not require that unaligned references
-   are permitted. */
-#if X86_MEMORY
+#ifdef WORDS_LITTEENDIAN
 
 #define WSAACHAR(s,v)				\
     do {					\