Re: [libvirt] [PATCH 05/24] maint: don't leave garbage on early API exit

On 01/02/2014 11:24 AM, John Ferlan wrote: Ooh, you make a good point. The caller has a bug in that case, and we could technically argue that they deserve the segfault (passing a bad pointer is the classic case of undefined behavior, and faulting will call attention to their bad code faster than an error code that might be ignored). But just because they deserve it doesn't mean we should do it, especially since it is a change in behavior for sloppy programs that currently get a nice error message but would now crash (we can't detect every single bad pointer, but NULL is a special case that is both more likely than any other bad pointer, and also easy enough to single out). So on the grounds of accommodating existing sloppy use, I'm thinking that it's best to change all of these to make the memset conditional on a non-NULL pointer, but still moving the memset to occur before other early exits (that is, we guarantee that if the buffer is valid, we clear it; and if the buffer is NULL, we guarantee a sane error message). My rework of this patch gets delayed to v2. By the way, the motivation behind this patch is functions like virConnectListAllDomains, which takes pains to ensure *domains is set to NULL regardless of error, but which DID play it safe: virConnectListAllDomains(virConnectPtr conn, virDomainPtr **domains, unsigned int flags) { VIR_DEBUG("conn=%p, domains=%p, flags=%x", conn, domains, flags); virResetLastError(); if (domains) *domains = NULL; -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org