test.cxx
------------------------------------------------------
#include <iostream>
struct A
{
unsigned short x:14;
unsigned short y:14;
};
extern unsigned n;
int main()
{
A a;
a.x = n & 0x3FFF;
a.y = (n>>14) & 0x3FFF;
unsigned expected = n & 0x3FFF;
if( a.x != expected )
{
std::cout << "test failed: "
<< " (x=" << a.x
<< ") != " << expected
<< ", y=" << a.y
<< std::endl;
return 1;
}
std::cout << "test succedeed" << std::endl;
return 0;
}
unsigned n = 0xFE7B4873U;
------------------------------------------------------
output:
test failed: (x=18547) != 2163, y=14829
14-bit unsigned field expands with non-zero padding bits
appears with gcc-4.2.1, gcc-4.1.2, gcc-4.2-20070822
does not appear with gcc-3.4.6
gcc was configured and built with crosstool-0.43 (with glibc-2.3.2)
powerpc-603-linux-gnu-g++ -v
Using built-in specs.
Target: powerpc-603-linux-gnu
Configured with:
/home/corpse/tmp/interlink/crosstool-0.43/build/powerpc-603-linux-gnu/gcc-4.2.1-glibc-2.3.2/gcc-4.2.1/configure
--target=powerpc-603-linux-gnu --host=i686-host_pc-linux-gnu
--prefix=/opt/compilers/gcc-4.2.1-glibc-2.3.2/powerpc-603-linux-gnu
--with-cpu=603 --enable-cxx-flags=-mcpu=603
--with-headers=/opt/compilers/gcc-4.2.1-glibc-2.3.2/powerpc-603-linux-gnu/powerpc-603-linux-gnu/include
--with-local-prefix=/opt/compilers/gcc-4.2.1-glibc-2.3.2/powerpc-603-linux-gnu/powerpc-603-linux-gnu
--disable-nls --enable-threads=posix --enable-symvers=gnu --enable-__cxa_atexit
--enable-languages=c,c++ --enable-shared --enable-c99 --enable-long-long
Thread model: posix
gcc version 4.2.1
--
Summary: bitfield optimizations causes corrupt bitfield expansion
at runtime
Product: gcc
Version: 4.2.1
Status: UNCONFIRMED
Severity: critical
Priority: P3
Component: c++
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: xk-corpse at hotmail dot com
GCC build triplet: i686-pc-linux-gnu
GCC host triplet: i686-pc-linux-gnu
GCC target triplet: powerpc-603-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33205
