[PATCH] configure: Avoid using strings binary

[Michal Privoznik]

When determining the endiandness of the target architecture we're
building for a small program is compiled, which in an obfuscated
way declares two strings. Then, we look which string is in
correct order (using strings binary) and deduct the endiandness.
But using the strings binary is problematic, because it's part of
toolchain (strings is just a symlink to
x86_64-pc-linux-gnu-strings or llvm-strings). And when
(cross-)compiling, it requires users to set the symlink to the
correct toolchain.

Fortunately, we have a better alternative anyways. Since we
require either clang or gcc we can rely on macros they declare.

Bug: https://bugs.gentoo.org/876933
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
---
 configure | 33 ++++++++++++++++++---------------
 1 file changed, 18 insertions(+), 15 deletions(-)

diff --git a/configure b/configure
index 45ee6f4eb3..91e04635cb 100755
--- a/configure
+++ b/configure
@@ -1426,27 +1426,30 @@ fi
 # ---
 # big/little endian test
 cat > $TMPC << EOF
-#include <stdio.h>
-short big_endian[] = { 0x4269, 0x4765, 0x4e64, 0x4961, 0x4e00, 0, };
-short little_endian[] = { 0x694c, 0x7454, 0x654c, 0x6e45, 0x6944, 0x6e41, 0, };
-int main(int argc, char *argv[])
-{
-    return printf("%s %s\n", (char *)big_endian, (char *)little_endian);
-}
+#if defined(__BYTE_ORDER) && __BYTE_ORDER == __BIG_ENDIAN || \
+    defined(__BIG_ENDIAN__)
+# error BIG
+#endif
+int main(void) { return 0; }
 EOF
 
 if compile_prog ; then
-    if strings -a $TMPE | grep -q BiGeNdIaN ; then
-        bigendian="yes"
-    elif strings -a $TMPE | grep -q LiTtLeEnDiAn ; then
-        bigendian="no"
-    else
-        echo big/little test failed
-        exit 1
-    fi
+  bigendian="yes"
 else
+  cat > $TMPC << EOF
+#if defined(__BYTE_ORDER) && __BYTE_ORDER == __LITTLE_ENDIAN || \
+    defined(__LITTLE_ENDIAN__)
+# error LITTLE
+#endif
+int main(void) { return 0; }
+EOF
+
+  if compile_prog ; then
+    bigendian="no"
+  else
     echo big/little test failed
     exit 1
+  fi
 fi
 
 ##########################################
-- 
2.35.1