From af795d1f88e9d8f1fad0613eac93c6775b4f6735 Mon Sep 17 00:00:00 2001
From: Eric Biggers <ebiggers3@gmail.com>
Date: Mon, 29 Dec 2014 21:26:06 -0600
Subject: [PATCH] Adjust endianness detection

__BYTE_ORDER__ isn't available in older gcc, unfortunately.
---
 configure.ac                  |  1 +
 include/wimlib/compiler-gcc.h | 12 +++++++++++-
 include/wimlib/compiler.h     |  2 +-
 3 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/configure.ac b/configure.ac
index e5e834f3..27d6fa38 100644
--- a/configure.ac
+++ b/configure.ac
@@ -5,6 +5,7 @@ AC_CONFIG_SRCDIR([src/wim.c])
 AC_CONFIG_MACRO_DIR([m4])
 AC_CONFIG_AUX_DIR([build-aux])
 AM_INIT_AUTOMAKE([-Wall -Werror subdir-objects foreign])
+AC_C_BIGENDIAN
 m4_ifdef([AM_PROG_AR], [AM_PROG_AR])
 LT_INIT
 
diff --git a/include/wimlib/compiler-gcc.h b/include/wimlib/compiler-gcc.h
index 46983308..cb42c894 100644
--- a/include/wimlib/compiler-gcc.h
+++ b/include/wimlib/compiler-gcc.h
@@ -27,7 +27,17 @@
 #define inline			inline __attribute__((always_inline))
 #define noinline		__attribute__((noinline))
 
-#define CPU_IS_BIG_ENDIAN	(__BYTE_ORDER__ == __ORDER_BIG_ENDIAN__)
+/* Newer gcc supports __BYTE_ORDER__.  Older gcc doesn't.  */
+#ifdef __BYTE_ORDER__
+#  define CPU_IS_BIG_ENDIAN	(__BYTE_ORDER__ == __ORDER_BIG_ENDIAN__)
+#elif defined(HAVE_CONFIG_H)
+#  include "config.h"
+#  ifdef WORDS_BIGENDIAN
+#    define CPU_IS_BIG_ENDIAN 1
+#  else
+#    define CPU_IS_BIG_ENDIAN 0
+#  endif
+#endif
 
 #if defined(__x86_64__) || defined(__i386__)
 #  define UNALIGNED_ACCESS_SPEED 3
diff --git a/include/wimlib/compiler.h b/include/wimlib/compiler.h
index 11eaa239..4bd92d78 100644
--- a/include/wimlib/compiler.h
+++ b/include/wimlib/compiler.h
@@ -59,7 +59,7 @@
 #endif
 
 #ifndef CPU_IS_BIG_ENDIAN
-#  error "missing required definition of CPU_IS_BIG_ENDIAN"
+#  error "missing required endianness definition"
 #endif
 
 #define CPU_IS_LITTLE_ENDIAN (!CPU_IS_BIG_ENDIAN)
-- 
2.43.0