preferring malloc over calloc

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c difference between malloc and calloc

Is there any situation where you would prefer malloc over calloc. i know both malloc and calloc allocate memory dynamically and that calloc also initializes all bits in alloted memory to zero. From this i would guess its always better to use calloc over malloc. Or is there some situations where malloc is better? Performance may be?

Voting to re-open this one. The other question is about the differences are. This question is different. It asks why one would prefer malloc (which is a common practice). — Raymond Hettinger, Aug 08 '15 at 02:37
@RaymondHettinger, if I remember correctly, that doesn't matter if their answers are the same. — Cristian Ciupitu, Aug 08 '15 at 03:33

score 26 · Accepted Answer · answered Nov 22 '10 at 05:19

26

If you need the dynamically allocated memory to be zero-initialized then use calloc.

If you don't need the dynamically allocated memory to be zero-initialized, then use malloc.

You don't always need zero-initialized memory; if you don't need the memory zero-initialized, don't pay the cost of initializing it. For example, if you allocate memory and then immediately copy data to fill the allocated memory, there's no reason whatsoever to perform zero-initialization.

calloc and malloc are functions that do different things: use whichever one is most appropriate for the task you need to accomplish.

answered Nov 22 '10 at 05:19

James McNellis

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Thanks.performance is a good point. I was also interested in knowing if there is any other possible reason. – user514946 Nov 22 '10 at 05:31
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(Ugh... they closed your question, which is slightly different than the "duplicate"... I hate S.O. sometimes.) Anyway, there are several reasons you may wish to use calloc over malloc. One is programs like valgrind will issue many potentially spurious warnings with malloc. Another is related to exposing bugs. Using uninitialized memory may result in erratic behavior that might make you notice a bug that would have otherwise gone unnoticed if you used calloc. – SO Stinks Apr 13 '13 at 07:05

score 2 · Answer 2 · answered Nov 22 '10 at 05:31

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Relying on calloc's zero-initialisation can be dangerous if you're not careful. Zeroing memory gives 0 for integral types and \0 for char types as expected. But it doesn't necessarily correspond to float/double 0 or NULL pointers.

answered Nov 22 '10 at 05:31

asdfjklqwer

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score 1 · Answer 3 · answered Nov 22 '10 at 05:32

You're normally allocating memory with the specific intent of storing something there. That means (at least most of) the space that's zero-initialized by calloc will soon be overwritten with other values. As such, most code uses malloc for a bit of extra speed with no real loss.

Nearly the only use I've seen for calloc was code that was (supposedly) benchmarking the speed of Java relative to C++. In the C++ version, it allocated some memory with calloc, then used memset to initialize the memory again in (what seemed to me) a fairly transparent attempt at producing results that favored Java.

preferring malloc over calloc

3 Answers3