From e6b61b98f46918d2770a0147a42d10f0a0e18ca8 Mon Sep 17 00:00:00 2001
From: Bernhard Rosenkraenzer <bero@arklinux.ch>
Date: Mon, 21 Mar 2011 12:19:36 +0100
Subject: Fix endianness detection with gcc 4.6 -flto -fwhole-program
Trying to build Qt with gcc 4.6 and the -flto optimization enabled
fails at ./configure state because the endianness can't be detected.
With -flto in QMAKE_CFLAGS and -fwhole-program in QMAKE_LFLAGS_APP,
gcc 4.6 manages to compute msb_bigendian[1] == lsb_littleendian[1] at
build time and reduces main() to "return 1;", throwing away the bits
being looked for.
Treating the short[] arrays as "code" and trying to actually run them
prevents even the -fwhole-program optimizer from kicking them out, and
since the endian test isn't actually run, doesn't break anything.
Merge-request: 1130
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@nokia.com>
---
config.tests/unix/endian/endiantest.cpp | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/config.tests/unix/endian/endiantest.cpp b/config.tests/unix/endian/endiantest.cpp
index 296f890..40b2c38 100644
--- a/config.tests/unix/endian/endiantest.cpp
+++ b/config.tests/unix/endian/endiantest.cpp
@@ -48,9 +48,9 @@ short lsb_littleendian[] = { 0x0000, 0x654c, 0x7361, 0x5374, 0x6769, 0x696e, 0x6
int main(int, char **)
{
// make sure the linker doesn't throw away the arrays
- char *msb_bigendian_string = (char *) msb_bigendian;
- char *lsb_littleendian_string = (char *) lsb_littleendian;
- (void) msb_bigendian_string;
- (void) lsb_littleendian_string;
+ void (*msb_bigendian_string)() = (void (*)())msb_bigendian;
+ void (*lsb_littleendian_string)() = (void (*)())lsb_littleendian;
+ (void)msb_bigendian_string();
+ (void)lsb_littleendian_string();
return msb_bigendian[1] == lsb_littleendian[1];
}
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