From mboxrd@z Thu Jan 1 00:00:00 1970 From: jgevaryahu@hotmail.com (Jonathan Gevaryahu) Date: Thu, 17 Sep 2015 00:42:17 -0400 Subject: [TUHS] Did realloc ever zero the new memory? In-Reply-To: <20150914032045.GM3796@eureka.lemis.com> References: <201509130032.t8D0WvPl024634@tahoe.cs.Dartmouth.EDU> <20150913011501.GF2103@mcvoy.com> <20150914032045.GM3796@eureka.lemis.com> Message-ID: On 9/13/2015 11:20 PM, Greg 'groggy' Lehey wrote: > On Sunday, 13 September 2015 at 16:09:55 +1000, Dave Horsfall wrote: >> On Sat, 12 Sep 2015, Larry McVoy wrote: >> >>> That's a really good point. Anyone like these? >>> >>> void *alloc(size_t bytes); >>> void *realloc(void *old, size_t want); >>> >>> void *zalloc(size_t bytes); >>> void *zealloc(void *old, size_t want); >>> >>> So alloc is new, we can have that. Realloc() is OK? Or not? Does the >>> current one have weird semantics? >>> >>> zalloc/zealloc are new, we can have those. >>> >>> If you guys like these I can push on Linus and the glibc people. >> I'll vote for those, although my dev days are pretty much over. I've >> never liked malloc() etc not clearing memory, although it has been, ahem, >> useful, in the past... > http://xkcd.com/927/ > > Greg Why not crealloc? pronounced 'cereal-oc'? it would behave the same as realloc, but explicitly zeroes the area upon allocating it (and maybe also upon reducing the size of the area, it zeroes the area freed, or zeroes the area the memory structure was previously located at, if the whole memory structure has to be moved.) Borrowing from http://pubs.opengroup.org/onlinepubs/009695399/functions/realloc.html : The /crealloc/() function shall change the size of the memory object pointed to by /ptr/ to the size specified by /size/. The contents of the object shall remain unchanged up to the lesser of the new and old sizes. If the new size of the memory object would require movement of the object, the space for the previous instantiation of the object is zeroed, then freed. If the new size is larger, the contents of the newly allocated portion of the object are explicitly set to the value of 0. If /size/ is 0 and /ptr/ is not a null pointer, the object pointed to is zeroed, then freed. If the space cannot be allocated, the object shall remain unchanged. If /ptr/ is a null pointer, /crealloc/() shall be equivalent to /calloc/() for the specified size. If /ptr/ does not match a pointer returned earlier by /calloc/() , /malloc/() , /realloc/() or /crealloc/() or if the space has previously been deallocated by a call to /free/() , /realloc/() or /crealloc/(), the behavior is undefined. The order and contiguity of storage allocated by successive calls to /crealloc/() is unspecified. The pointer returned if the allocation succeeds shall be suitably aligned so that it may be assigned to a pointer to any type of object and then used to access such an object in the space allocated (until the space is explicitly freed or reallocated). Each such allocation shall yield a pointer to an object disjoint from any other object. The pointer returned shall point to the start (lowest byte address) of the allocated space. If the space cannot be allocated, a null pointer shall be returned. -- Jonathan Gevaryahu AKA Lord Nightmare jgevaryahu at gmail.com jgevaryahu at hotmail.com -------------- next part -------------- An HTML attachment was scrubbed... URL: