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Frees a block of thread-local memory that was originally allocated using DosAllocThreadLocalMemory.


DosFreeThreadLocalMemory (p)


p (ULONG *) - input
Address of the memory block to free.

Return Code

rc (APIRET) - returns
This function returns one of the following values:
  • 0 NO_ERROR


When a process is started, a small block of memory is set aside to be used as a thread-local memory area. This memory is at the same virtual address for each thread, but is backed by different physical memory. This permits each thread to have a small block of memory that is unique, or local, to that thread.

The thread-local memory area consists of 32 DWORDs (128 bytes), each DWORD being 32-bits in size.

Example Code

This example shows how to allocate and free 3 DWORDs of local thread memory.

#include <os2.h>
#include <stdio.h>          /* Needed for printf */

PULONG   pulThreadDWords = NULL;     /* Pointer to thread DWORDs returned */
APIRET   rc              = NO_ERROR; /* Return code */

int main(VOID) {

         /* Allocate 3 DWORDs of local thread memory */

  rc = DosAllocThreadLocalMemory(3,                   /* Number of DWORDs */
                                 &pulThreadDWords);   /* Address returned */

  if (rc != NO_ERROR) {
    printf("DosAllocThreadLocalMemory error: return code = %u\n", rc);
    return 1;

          /* ... Use the thread-local memory ... */

  rc = DosFreeThreadLocalMemory(pulThreadDWords);     /* Free the DWORDs */

  if (rc != NO_ERROR) {
    printf("DosFreeThreadLocalMemory error: return code = %u\n", rc);
    return 1;

  return NO_ERROR;

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