_uopen - Open Heap for Use

Syntax

#include <umalloc.h>
int _uopen(Heap_t heap);

uopen allows the current process to use the heap you specify. If the heap is shared, you must call _uopen in each process that will allocate or free from the heap. See "Managing Memory" in the VisualAge C++ Programming Guide for more information about sharing heaps, and about creating and using heaps in general.

If successful, _uopen returns 0. A nonzero return code indicates failure. Passing _uopen a heap that is not valid results in undefined behavior.

The following example creates a fixed-size heap, then uses _uopen to open it. The program then performs operations on the heap, and closes and destroys it.

#define  INCL_DOSMEMMGR             /* Memory Manager values */
#include <os2.h>
#include <bsememf.h>                /* Get flags for memory management  */
#include <stdlib.h>
#include <stdio.h>
#include <umalloc.h>

int main(void)
{
   void    *initial_block;
   APIRET  rc;
   Heap_t  myheap;
   char    *p;

   /* Call DosAllocMem to get the initial block of memory */
   if (0 != (rc = DosAllocMem(&initial_block, 65536,
                              PAG_WRITE | PAG_READ | PAG_COMMIT))) {
      printf("DosAllocMem error: return code = %ld\n", rc);
      exit(EXIT_FAILURE);
   }
   /* Create a fixed size heap starting with the block declared earlier */
   if (NULL == (myheap = _ucreate(initial_block, 65536, _BLOCK_CLEAN,
                                  _HEAP_REGULAR, NULL, NULL))) {
      puts("_ucreate failed.");
      exit(EXIT_FAILURE);
   }
   if (0 != _uopen(myheap)) {
      puts("_uopen failed.");
      exit(EXIT_FAILURE);
   }
   p = _umalloc(myheap, 100);
   free(p);
   if (0 != _uclose(myheap)) {
      puts("_uclose failed");
      exit(EXIT_FAILURE);
   }
   if (0 != (rc = DosFreeMem(initial_block))) {
      printf("DosFreeMem error: return code = %ld\n", rc);
      exit(EXIT_FAILURE);
   }
   return 0;
}

uaddmem
uclose
ucreate
Managing Memory" in the VisualAge C++ Programming Guide

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