On 04/01/2014 09:28 AM, Ondrej Oprala wrote: > Hi, > Could someone please explain to me, why are xrealloc and xfree (or more > specifically - their parts) from lib/malloc/xmalloc.c necessary? > > e.g. > if (string) > free(string); > Why is this needed? AFAIK the C standard specifies free(NULL) is > completely legal.
Bruno Haible argued that the cost of a redundant if conditional is cheaper than the cost of a function call in profiling runs, at least in the portions of gnulib where he used that idiom. Personally, I like getting rid of the redundant if (I think the extra CPU cycles spent are in the noise, until given a profile dump that proves otherwise). > Also: > temp = pointer ? realloc (pointer, bytes) : malloc (bytes); > Again, the C standard says that realloc(0, bytes) is equivalent to > malloc(bytes). There's no good reason for this one; probably just extremely old legacy code back in the day when various libc were not compatible to the restrictions added in later versions of the C standard. -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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