Red Hat Bugzilla – Bug 426181
4.1.2 20070925 (Red Hat 4.1.2-33) -fstrict-aliasing causes skipped code
Last modified: 2007-12-19 02:55:00 EST
Description of problem: This problem is described in detail in http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32328 Which says gnu.org's 4.1.2 is clean of this bug. That fix needs to be backported to Redhat 4.1.2-33 and Fedora 4.1.2 20070925 Version-Release number of selected component (if applicable): Fedora 4.1.2 20070925 (Redhat 4.1.2-33) How reproducible: Steps to Reproduce: 1. 2. 3. Actual results: Expected results: Additional info:
The symptoms appear when compiling kernel module drivers/net/wireless/b43/rfkill.c The code that calls KEY_WLAN 1 and KEY_WLAN 0 is optimized out. This is why Fedora 2.6.22-1.42 (f8 x86_64) worked in lighting the LED and Fedora 2.6.22-1.49 (same arch) didn't. Same code, different compilation result. There are additional examples in the references bugzillas... just thought I'd add a Fedora-specific one. I'm not a compiler-internals guy. Just pointing out this was patched in the gnu 4.1.2 but not in the RH/F 4.1.2.
Kernel modules should be compiled with -fno-strict-aliasing anyway, kernel violates aliasing in hundreds of places. If you read the PR properly, it would be clear this is a WONTFIX for 4.1.x/4.2.x, the changes aren't really backportable to earlier GCC versions and are massive.