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The function calloc allocates memory and clears it to zero. It
is declared in stdlib.h.
This function allocates a block long enough to contain a vector of count elements, each of size eltsize. Its contents are cleared to zero before
callocreturns.
You could define calloc as follows:
void *
calloc (size_t count, size_t eltsize)
{
size_t size = count * eltsize;
void *value = malloc (size);
if (value != 0)
memset (value, 0, size);
return value;
}
But in general, it is not guaranteed that calloc calls
malloc internally. Therefore, if an application provides its own
malloc/realloc/free outside the C library, it
should always define calloc, too.