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Calloc () and NULL

I know that calloc allocates memory and writes zeros to each cell, so my question is, is there a difference between using calloc or using malloc and running over cells that write NULL? Are calloc zeros equivalent to NULL?

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No, they are not always equivalent, but on the most popular machines everything will be fine. calloc

writes a bit pattern of all zeros to the allocated memory, but the null pointer value may not be completely bit-zero on some machines (or even for some types on some machines).



Check out the Null Pointers section in the C FAQ for a lot of information.

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NULL does not guarantee that all bits are set to 0, even if it is always compared to the integer constant 0.

Calloc will set all bits to 0 just like calling memset. It is acceptable that the resulting value (s) will not be compared to NULL.



Therefore, they are not equivalent.

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