reallocarr(3) - NetBSD Manual Pages

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REALLOCARR(3)           NetBSD Library Functions Manual          REALLOCARR(3)


NAME

     reallocarr -- reallocate array


SYNOPSIS

     #include <stdlib.h>

     int
     reallocarr(void *ptrp, size_t number, size_t size);


DESCRIPTION

     The reallocarr function safely allocates, resizes, or frees arrays in
     memory.

     If ptr is a null pointer, or a pointer to memory previously allocated
     with reallocarr, then reallocarr(&ptr, ,,number, ,, size) allocates or
     reallocates the memory that ptr points to, possibly moving it to a dif-
     ferent location in memory, so that it has space for an array of number
     elements of size bytes apiece.  reallocarr updates ptr in case it was
     moved on success, and leaves it unchanged on failure.

     If ptr was previously allocated, the objects stored at ptr[0], ptr[1],
     ..., up to the shorter of its old number and its new number, are copied
     into the new memory, like realloc(3).

     ptr may be null and number may be zero.  size must be nonzero.

     The memory allocated by reallocarr may be freed with reallocarr(&ptr, ,0,
     , size), which will always succeed and unconditionally set ptr to null.

     Like calloc(3), reallocarr fails gracefully if the product of number and
     size would overflow the representable size of memory.  Unlike calloc(3),
     new memory allocated by reallocarr is not zero-initialized.

     The reallocarr function may alter errno as a side effect.

     Note that the argument ptrp is a pointer to a pointer to allocated mem-
     ory, unlike realloc(3) which takes a pointer to allocated memory.


RETURN VALUES

     On successful completion, reallocarr returns 0 and updates ptr.  Other-
     wise, an errno(2) is returned, and ptr and the memory it points to are
     unmodified.


EXAMPLES

     The following uses reallocarr() to initialize an array of INITSIZE inte-
     gers, then resizes it to NEWSIZE elements, and finally frees it:

           int *data = NULL;
           int error = 0;

           /* allocate */
           error = reallocarr(&data, INITSIZE, sizeof(*data));
           if (error)
                   errc(1, error, "reallocarr failed");
           ...
           /* resize */
           error = reallocarr(&data, NEWSIZE, sizeof(*data));
           if (error)
                   errc(1, error, "reallocarr failed on resize");
           ...
           /* free */
           (void)reallocarr(&data, 0, sizeof(*data));
           assert(data == NULL);


SEE ALSO

     calloc(3), realloc(3), reallocarray(3)


HISTORY

     reallocarr first appeared in NetBSD 7.0.  OpenBSD introduced the
     reallocarray(3) function for the same purpose, but the interface makes it
     difficult to correctly handle zero-sized allocations.

NetBSD 10.1                     August 31, 2022                    NetBSD 10.1