malloc() — Reserve Storage Block


#include <stdlib.h>
void *malloc(size_t size);

Language Level





The malloc() function reserves a block of storage of size bytes. Unlike the calloc() function, malloc() does not initialize all elements to 0. The maximum size for a non-teraspace malloc() is 16711568 bytes.

  1. All heap storage is associated with the activation group of the calling function. As such, storage should be allocated, deallocated, and reallocated within the same activation group. You cannot allocate heap storage within one activation group and deallocate or reallocate that storage from a different activation group. For more information about activation groups, see the ILE Concepts manual.
  2. To use teraspace storage instead of single-level store storage without changing the C source code, specify the TERASPACE(*YES *TSIFC) parameter on the compiler command. This maps the malloc() library function to _C_TS_malloc(), its teraspace storage counterpart. The maximum amount of teraspace storage that can be allocated by each call to _C_TS_malloc() is 2GB - 224, or 2147483424 bytes. If more than 2147483408 bytes are needed on a single request, call _C_TS_malloc64(unsigned long long int);.

    For more information, see the ILE Concepts manual.

  3. For current statistics on the teraspace storage being used by MI programs in an activation group, call the _C_TS_malloc_info function. This function returns information including total bytes, allocated bytes and blocks, unallocated bytes and blocks, requested bytes, pad bytes, and overhead bytes. To get more detailed information about the memory structures used by the _C_TS_malloc() and _C_TS_malloc64() functions, call the _C_TS_malloc_debug() function. You can use the information this function returns to identify memory corruption problems.
  4. If the Quick Pool memory manager has been enabled in the current activation group, then the storage is retrieved using Quick Pool memory manager. See _C_Quickpool_Init() — Initialize Quick Pool Memory Manager for more information.

Return Value

The malloc() function returns a pointer to the reserved space. The storage space to which the return value points is suitably aligned for storage of any type of object. The return value is NULL if not enough storage is available, or if size was specified as zero.


This example prompts for the number of array entries you want and then reserves enough space in storage for the entries. If malloc() was successful, the example assigns values to the entries and prints out each entry; otherwise, it prints out an error.
#include <stdio.h>
#include <stdlib.h>
int main(void)
  long * array;    /* start of the array */
  long * index;    /* index variable     */
  int    i;        /* index variable     */
  int  num;        /* number of entries of the array */
  printf( "Enter the size of the array\n" );
  scanf( "%i", &num );
  /* allocate num entries */
  if ( (index = array = (long *) malloc( num * sizeof( long ))) != NULL )
    for ( i = 0; i < num; ++i )           /* put values in array    */
       *index++ = i;                      /* using pointer notation */
    for ( i = 0; i < num; ++i )           /* print the array out    */
      printf( "array[ %i ] = %i\n", i, array[i] );
  else { /* malloc error */
    perror( "Out of storage" );
/********************  Output should be similar to:  **************
Enter the size of the array
array[ 0 ] = 0
array[ 1 ] = 1
array[ 2 ] = 2
array[ 3 ] = 3
array[ 4 ] = 4

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