Re: [libvirt] [PATCHv2] virsh: avoid uninitialized memory usage

On 04/19/2012 06:43 PM, Wen Congyang wrote: Thanks for searching. This is a bug in theory: POSIX requires that you use sa_sigaction if sa_flags includes SA_SIGINFO, and that you use sa_handler otherwise, and while it permits sa_handler and sa_sigaction to overlap, it does not require this. Thankfully, in practice, I know of no platform where sa_sigaction and sa_handler do not overlap; furthermore, I don't know of any commonly used ABIs where casting a 1-arg function pointer and calling it with 3 arguments breaks (the extra 2 args are ignored by the callee); likewise, commonly used ABIs state that if you cast a 3-arg function pointer and call it with only 1 argument, you have predictable behavior so long as you limit yourself to the first argument (but you _are_ likely to misbehave if you try to access the other two arguments). Again, practice says it will work, but theory says you can't rely on it to work, so we should fix it. Do you want to prepare the patch, or shall I? Gnulib doesn't guarante SA_SIGINFO, but it _does_ guarantee that for all platforms where SA_SIGINFO is not defined, then sa_sigaction overlaps with sa_handler, and that such platforms have a calling convention . Therefore, on those platforms, we end up installing a sa_handler, and given my above statements about practice, as long as we don't access the second or third argument, we won't trigger any odd behaviors. Yep, definite bug for mingw. -- Eric Blake eblake(a)redhat.com +1-919-301-3266 Libvirt virtualization library http://libvirt.org