On Mon, Apr 30, 2018 at 09:20:29AM -0400, John Ferlan wrote: > > > On 04/25/2018 11:55 AM, Marc Hartmayer wrote: > > 1. Don't allocate if there is nothing that needs to be > > allocated. Especially as the result of calling calloc(0, ...) is > > implementation-defined. > > Following VIR_ALLOC_N one finds : > > VIR_ALLOC_N(params_val, nparams) > > which equates to > > # define VIR_ALLOC_N(ptr, count) \ > virAllocN(&(ptr), sizeof(*(ptr)), (count), true, \ > VIR_FROM_THIS, __FILE__, __FUNCTION__, __LINE__) > > or > > virAllocN(¶ms_val, sizeof(params_val), nparams, true, ...) > > and eventually/essentially > > *params_val = calloc(sizeof(params_val), nparams) > > If the returned value is NULL then we error w/ OOM (4th param=true). > > So, unless @params_val had no elements, it won't be calloc(0,...) and > thus the question becomes is there a more specific path you are > referencing here? > > FWIW: My f26 man page for calloc says: > > "The calloc() function allocates memory for an array of nmemb elements > of size bytes each and returns a pointer to the allocated memory. The > memory is set to zero. If nmemb or size is 0, then calloc() returns > either NULL, or a unique pointer value that can later be successfully > passed to free()" > > We have so many places in the code that use VIR_ALLOC_N and do not check > if the sizeof() or count is 0 - which makes me wonder even more about > the specific case in which you are referencing. I looked through the > various remote_protocol.x structures that would use this and it seems > they all use remote_typed_param for the structure being returned, so > it's not clear how any of them could have a sizeof() returning 0.
If there is any problem with this, then we should just change bootstrap.conf to use calloc-gnu instead of calloc-posix, which basically turns calloc(0) into calloc(1) for compat with glibc behaviour. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :| -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
