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alloca() Allocate Memory Block on Stack
#include <malloc.h> Required for declarations only
char *alloca(size); Returns pointer to allocated space
unsigned size; Number of bytes to allocate on stack
alloca() allocates 'size' bytes on the program's stack. This space is
automatically freed when the function that called alloca() is exited.
Returns: A char pointer to allocated space. Returns NULL (defined
in <stdio.h>) if the space cannot be allocated.
Notes: Do not pass the pointer returned by alloca() as an
argument to free(); the space will be automatically freed
upon exit from the function that called alloca().
Because alloca() manipulates the stack, it should be used
only in simple assignment statements and NEVER in an
expression that is an argument to a function.
-------------------------------- Example ---------------------------------
The following statements demonstrate a call to alloca() that
allocates space for 20 integers on the stack:
#include <malloc.h>
#include <stdio.h> /* for printf and NULL */
func(x)
int x;
{
int *intptr;
/* allocate 'x' ints in a simple expression */
intptr = (int *) alloca(x * sizeof(int));
if (intptr == NULL) {
printf("not enough stack space\n");
return;
}
.
.
/* 'intptr' is automatically "freed" on exit */
}
main()
{
func(20);
}
See Also:
calloc()
malloc()
realloc()
stackavail()
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