PR29961, plugin-api.h: "Could not detect architecture endianess"

[Alan Modra]

Found when attempting to build binutils on sparc sunos-5.8 where
sys/byteorder.h defines _BIG_ENDIAN but not any of the BYTE_ORDER
variants.  This patch adds the extra tests to cope with the old
machine, and tidies the header a little.

If you're wondering why I bother with the tidy, it's because the other
patches in the PR included sys/byteorder.h (again!) and added tests
specific to sunos-5.8 immediately after.  No doubt that was following
the same practice as for __GLIBC__.  If glibc's endian.h had been
treated the same as other headers included here, we'd probably have
seen better fixes.

	PR 29961
	plugin-api.h: When handling non-gcc or gcc < 4.6.0 include
	necessary header files before testing macros.  Make more use
	of #elif.  Test _LITTLE_ENDIAN and _BIG_ENDIAN in final tests.

diff --git a/include/plugin-api.h b/include/plugin-api.h
index 395d5bcc598..f3cf2d8101b 100644
--- a/include/plugin-api.h
+++ b/include/plugin-api.h
@@ -37,7 +37,7 @@
 #error cannot find uint64_t type
 #endif
 
-/* Detect endianess based on __BYTE_ORDER__ macro.  */
+/* Detect endianess based on gcc's (>=4.6.0) __BYTE_ORDER__ macro.  */
 #if defined(__BYTE_ORDER__) && defined(__ORDER_BIG_ENDIAN__) && \
     defined(__ORDER_LITTLE_ENDIAN__) && defined(__ORDER_PDP_ENDIAN__)
 #if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
@@ -47,46 +47,47 @@
 #elif __BYTE_ORDER__ == __ORDER_PDP_ENDIAN__
 #define PLUGIN_PDP_ENDIAN 1
 #endif
+
 #else
-/* Older GCC releases (<4.6.0) can make detection from glibc macros.  */
+/* Include header files to define endian macros.  */
 #if defined(__GLIBC__) || defined(__GNU_LIBRARY__) || defined(__ANDROID__)
 #include <endian.h>
+
+#elif defined(__SVR4) && defined(__sun)
+#include <sys/byteorder.h>
+
+#elif defined(__FreeBSD__) || defined(__NetBSD__) || \
+      defined(__DragonFly__) || defined(__minix)
+#include <sys/endian.h>
+
+#elif defined(__OpenBSD__)
+#include <machine/endian.h>
+#endif
+
+/* Detect endianess based on __BYTE_ORDER.  */
 #ifdef __BYTE_ORDER
 #if __BYTE_ORDER == __LITTLE_ENDIAN
 #define PLUGIN_LITTLE_ENDIAN 1
 #elif __BYTE_ORDER == __BIG_ENDIAN
 #define PLUGIN_BIG_ENDIAN 1
 #endif
-#endif
-#endif
-/* Include all necessary header files based on target.  */
-#if defined(__SVR4) && defined(__sun)
-#include <sys/byteorder.h>
-#endif
-#if defined(__FreeBSD__) || defined(__NetBSD__) || \
-    defined(__DragonFly__) || defined(__minix)
-#include <sys/endian.h>
-#endif
-#if defined(__OpenBSD__)
-#include <machine/endian.h>
-#endif
+
 /* Detect endianess based on _BYTE_ORDER.  */
-#ifdef _BYTE_ORDER
+#elif defined _BYTE_ORDER
 #if _BYTE_ORDER == _LITTLE_ENDIAN
 #define PLUGIN_LITTLE_ENDIAN 1
 #elif _BYTE_ORDER == _BIG_ENDIAN
 #define PLUGIN_BIG_ENDIAN 1
 #endif
-#endif
+
 /* Detect based on _WIN32.  */
-#if defined(_WIN32)
+#elif defined _WIN32
 #define PLUGIN_LITTLE_ENDIAN 1
-#endif
+
 /* Detect based on __BIG_ENDIAN__ and __LITTLE_ENDIAN__ */
-#ifdef __LITTLE_ENDIAN__
+#elif defined __LITTLE_ENDIAN__ || defined _LITTLE_ENDIAN
 #define PLUGIN_LITTLE_ENDIAN 1
-#endif
-#ifdef __BIG_ENDIAN__
+#elif defined __BIG_ENDIAN__ || defined _BIG_ENDIAN
 #define PLUGIN_BIG_ENDIAN 1
 #endif
 #endif

-- 
Alan Modra
Australia Development Lab, IBM