malloc
Defined in header <stdlib.h>
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Allocates size
bytes of uninitialized storage.
If allocation succeeds, returns a pointer to the lowest (first) byte in the allocated memory block that is suitably aligned for any object type with fundamental alignment.
If size
is zero, the behavior is implementation defined (null pointer may be returned, or some non-null pointer may be returned that may not be used to access storage, but has to be passed to free
).
A previous call to |
(since C11) |
Parameters
size | - | number of bytes to allocate |
Return value
On success, returns the pointer to the beginning of newly allocated memory. To avoid a memory leak, the returned pointer must be deallocated with free()
or realloc()
.
On failure, returns a null pointer.
Example
#include <stdio.h>
#include <stdlib.h>
int main(void)
{
int *p1 = malloc(4*sizeof(int)); // allocates enough for an array of 4 int
int *p2 = malloc(sizeof(int[4])); // same, naming the type directly
int *p3 = malloc(4*sizeof *p3); // same, without repeating the type name
if(p1) {
for(int n=0; n<4; ++n) // populate the array
p1[n] = n*n;
for(int n=0; n<4; ++n) // print it back out
printf("p1[%d] == %d\n", n, p1[n]);
}
free(p1);
free(p2);
free(p3);
}
Output:
p1[0] == 0
p1[1] == 1
p1[2] == 4
p1[3] == 9
References
C11 standard (ISO/IEC 9899:2011):
- 7.22.3.4 The malloc function (p: 349)
C99 standard (ISO/IEC 9899:1999):
- 7.20.3.3 The malloc function (p: 314)
C89/C90 standard (ISO/IEC 9899:1990):
- 4.10.3.3 The malloc function
See also
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