From 33ab5f24913db8d5590fe4155829bd38e7902506 Mon Sep 17 00:00:00 2001
Message-Id: <33ab5f24913db8d5590fe4155829bd38e7902506.1666164897.git.mprivozn@redhat.com>
From: Michal Privoznik <mprivozn@redhat.com>
Date: Fri, 14 Oct 2022 09:30:15 +0200
Subject: [PATCH] configure: Avoid using strings binary

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. We can mimic
what compiler.h is already doing: comparing __BYTE_ORDER__
against values for little/big endiandness.

Bug: https://bugs.gentoo.org/876933
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Message-Id: <d6d9c7043cfe6d976d96694f2b4ecf85cf3206f1.1665732504.git.mprivozn@redhat.com>
Cc: qemu-stable@nongnu.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 configure | 35 ++++++++++++++++++-----------------
 1 file changed, 18 insertions(+), 17 deletions(-)

diff --git a/configure b/configure
index f9ec050bf8..81561be7c1 100755
--- a/configure
+++ b/configure
@@ -1423,30 +1423,31 @@ if test "$tcg" = "enabled"; then
     git_submodules="$git_submodules tests/fp/berkeley-softfloat-3"
 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__ == __ORDER_LITTLE_ENDIAN__
+# error LITTLE
+#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
+if ! compile_prog ; then
+  bigendian="no"
 else
+  cat > $TMPC << EOF
+#if defined(__BYTE_ORDER__) && __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+# error BIG
+#endif
+int main(void) { return 0; }
+EOF
+
+  if ! compile_prog ; then
+    bigendian="yes"
+  else
     echo big/little test failed
     exit 1
+  fi
 fi
 
 ##########################################
-- 
2.37.3