From: "Nick van der Merwe" <NEEK AT cerecam DOT uct DOT ac DOT za>
To: djgpp AT sun DOT soe DOT clarkson DOT edu
Date:          Wed, 11 May 1994 12:15:02 SAST-2
Subject:       .._remaining_physical_memory()

My previous postings on this problem were in a huge mess, hence no 
replies. I do apologise. This is the problem:

I have been doing dynamic memory allocation using malloc,calloc and 
free. Now with v1.11 I tried using 
_go32_dpmi_remaining_physical_memory() to check what happens to my 
memory. I compiled the program below with maint4, and ran it under 
DOS and in a Windows DOS Box.

In Windows it indicated that no memory had been allocated, and in DOS 
it kept on indicating the wrong values e.g. indicating that 16K has 
been allocated for a 100byte array etc. (16K the page size?)

A similar 2-D allocation routine a la Dr. John Weiss has been used 
and tested using this function. This shows the correct values being 
allocated(using calloc) + small overhead, but it doesn't indicate the 
data blocks being freed.

The simple example below has been tested using BorlandC++, 
substituting farcoreleft() for 
_go32_dpmi_remaining_physical_memory(). In this case it worked 
perfectly.

Is the problem with my code,.._remaining_physical_memory() or with 
the malloc() and free() commands not giving back the memory?

I notice a similar question was posted on memory in DV/X.

----------------------------------------------------------------------
#include <dpmi.h>
#include <std.h>
#include <malloc.h>
#include <math.h>
#include "nutils.h"

unsigned char *ucline;
int *iline;

int main()
{
  unsigned long phys_mem,virt_mem,oldmem,newmem,allocmem,expected;
  int width,n;

  width=512;
  phys_mem=_go32_dpmi_remaining_physical_memory();
  virt_mem=_go32_dpmi_remaining_virtual_memory();
  printf("start: physical memory = %ld , virtual memory =  
%ld\n",phys_mem,virt_mem);

  /*
  //  Test 1-D arrays
  */

  printf("\nInput vector size: ");
  scanf("%d",&width);

  oldmem=phys_mem;

  ucline=(unsigned char *)malloc(width*sizeof(unsigned char));

  newmem=_go32_dpmi_remaining_physical_memory();
  allocmem=oldmem-newmem;
  expected=(unsigned long)(width*sizeof(unsigned char));

  printf("UCvector(%d): allocated = %ld , expected = %ld ,diff = 
%ld\n",width,allocmem,expected,allocmem-expected);

  free(ucline);

  newmem=_go32_dpmi_remaining_physical_memory();
  printf("After freeing: memory now = %ld , expected = %ld , 
difference = %ld\n",newmem,oldmem,labs(newmem-oldmem));

  oldmem=newmem;


  iline=(int *)malloc(width*sizeof(int));

  newmem=_go32_dpmi_remaining_physical_memory();
  allocmem=oldmem-newmem;
  expected=(unsigned long)(width*sizeof(int));

  printf("Ivector(%d): allocated = %ld , expected = %ld ,diff = 
%ld\n",width,allocmem,expected,allocmem-expected);

  /* write to vector */
  for(n=0;n<width;++n)
                      iline[n]=0;

  free(iline);


  newmem=_go32_dpmi_remaining_physical_memory();
  printf("After freeing: memory now = %ld , expected = %ld , 
difference = %ld\n",newmem,oldmem,labs(newmem-oldmem));

  getkey();
  return(0);
}
----------------------------------------------------------------------
Nick van der Merwe
Department of Surveying and Geodetic Engineering
University of Cape Town | 
South Africa            |       "Welcome to the Gnu South Africa"
Internet: neek AT cerecam DOT uct DOT ac DOT za