http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46620
Summary: 32-bit structures containing bitfields are not copied
correctly on -O2 , x86 backend
Product: gcc
Version: 4.4.3
Status: UNCONFIRMED
Severity: major
Priority: P3
Component: c
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: bnitule...@tremend.ro
Created attachment 22499
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=22499
Test case exhibiting the error
The attached code contains a copy between two structures containing bitfields.
The x86 code generated on -O2 fails to copy two fields in the structure. It is
also very complex, trying to break the structure in sets of bitfields and copy
them independently.
I have attached an archive containing
- file exhibiting the error (bitfield-error.c)
- main file driving the example
- generated assembly code (gcc -c -O2 bitfield-error.c -S)
To run the code in the attachment
gcc -c -O2 bitfield-error.c
gcc -c -O0 bitfield-error-main.c
gcc -o bitfield-error bitfield-error.o bitfield-error-main.o
./bitfield-error
Result: 0, expected 1
Running at -O0 gives a different answer
gcc -c -O0 bitfield-error.c
gcc -o bitfield-error bitfield-error.o bitfield-error-main.o
./bitfield-error
Result: 1, expected 1
The gcc used is the one from Ubuntu 10.04.1 LTS :
$ gcc --version
gcc (Ubuntu 4.4.3-4ubuntu5) 4.4.3
Copyright (C) 2009 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
$ gcc -v
Using built-in specs.
Target: i486-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu 4.4.3-4ubuntu5'
--with-bugurl=file:///usr/share/doc/gcc-4.4/README.Bugs
--enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr --enable-shared
--enable-multiarch --enable-linker-build-id --with-system-zlib
--libexecdir=/usr/lib --without-included-gettext --enable-threads=posix
--with-gxx-include-dir=/usr/include/c++/4.4 --program-suffix=-4.4 --enable-nls
--enable-clocale=gnu --enable-libstdcxx-debug --enable-plugin --enable-objc-gc
--enable-targets=all --disable-werror --with-arch-32=i486 --with-tune=generic
--enable-checking=release --build=i486-linux-gnu --host=i486-linux-gnu
--target=i486-linux-gnu
Thread model: posix
gcc version 4.4.3 (Ubuntu 4.4.3-4ubuntu5)
