Re: [libvirt] [PATCH] Cygwin's GCC doesn't like this .sa_handler initialization for some reason

On 04/25/2010 05:32 AM, Matthias Bolte wrote: ACK. By the way, the "for some reason" boils down to how sa_handler is declared in <signal.h> on the two platforms. On cygwin, sa_handler happens to be a member of an anonymous union (exploiting a gcc extension); whereas on Linux, it is a macro that accesses a member of a named union. If I read POSIX correctly, both behaviors for the declaration of sa_handler are permitted. But dotted assignment only works in the case of a named union. Whether it is a gcc bug that you can't use dotted assignment to access a member of an anonymous union, or a cygwin bug for having a header that does not allow compilation like Linux (when cygwin's stated goal is to be Linux-compatible) is debatable. By the way, this use of memset() to initialize action_stop assumes that the null pointer is all 0 bits (which is probably okay for all platforms that libvirt will ever run on). There is currently a discussion on gnulib on the fact that to be portable to C99, where a null pointer might not be all 0 bits, you would instead have to use the more drawn-out sequence: static struct sigaction zero_sigaction = {0}; struct sigaction action_stop = zero_sigaction; action_stop.sa_handler = stop; But don't go changing this commit just for that theoretical platform. -- Eric Blake eblake(a)redhat.com +1-801-349-2682 Libvirt virtualization library http://libvirt.org