CMake/Source/kwsys/RequireLargeFilesSupport.cxx

#define _LARGEFILE_SOURCE
#define _LARGE_FILES
#define _FILE_OFFSET_BITS 64
#include <sys/types.h>
#include <sys/stat.h>
#include <assert.h>
#include <stdio.h>

int main( int, char **argv )
{
  // check that off_t can hold 2^63 - 1 and perform basic operations...
#define OFF_T_64 (((off_t) 1 << 62) - 1 + ((off_t) 1 << 62))
  if (OFF_T_64 % 2147483647 != 1)
    return 1;

  // stat breaks on SCO OpenServer
  struct stat buf;
  stat( argv[0], &buf );
  if (!S_ISREG(buf.st_mode))
    return 2;

  FILE *file = fopen( argv[0], "r" );
  off_t offset = ftello( file );
  fseek( file, offset, SEEK_CUR );
  fclose( file );
  return 0;
}