help request. seg fault when dereferencing pointer to large structure

[thomas ferris]

Dear gcc guru,

 

I'm using gcc 2.95.3 on a 2.4 GHz Xeon with 4GB of ram running redhat linux with the 2.4.20 and/or 2.4.27 kernel.  For the project I'm working on, I have no choice but to use 2.95.3.

 

If I create a large structure, then create a pointer to that structure, then use the pointer to reference areas of the structure more than 0xfffffff bytes from the beginning of the structure, I get a seg fault.

 

In the attached sample code, the "got here 3" prints, but the "got here 4" does not.  The line of code between those lines produces the seg fault.

 

I know the memory for the structure is getting allocated, and calloc never fails, so the allocated memory can be written.

 

Based on what I've seen, I would guess that whatever assembly language addressing mode is being used has an offset limit of 0xfffffff.

 

I look forward to any help you may be able to provide.

 

Thank you very much,

 

Mark

 

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#include <stdio.h>
#include <stdlib.h>

typedef struct
{
  int begin;

  int middle[100000000];

  int end;
} big_str;


void main (void)
{
  big_str  *bp;

  bp = calloc (sizeof(big_str));

  if (bp == NULL)
  {
    printf ("malloc failed \n");
    exit (1);
  }

  printf ("got here 1 \n");
  bp->begin = 1;
  printf ("got here 2 \n");
  bp->middle[0] = 1;
  printf ("got here 3 \n");
  bp->middle[67108862] = 1;
  printf ("got here 4 \n");
  bp->middle[67108863] = 1;
  printf ("got here 5 \n");
  bp->end = 1;
  printf ("got here 6 \n");

} /* end main */