🚀 go-pugleaf

When manipulating obscenely large structures...

For gcc2.3.1 target==host==sparc-sun-sunos4.1, the program at the bottom
prints out (lines marked '*' are my editing to show errors)
* sizeof(struct RootSection) == 0xf0000000, 3840 Mb
* sizeof(struct RootMemory) == 0xf0000000, 3840 Mb
  &p->instruction_buffer = 0xc0000000
  &p->outbound_buffer = 0xd0000000
* &p->inbound_buffer = 0xc0000000
For gcc2.3.1, target==host==dec-mips-ultrix, the same program prints out
  sizeof(struct RootSection) == 0x10000000, 256 Mb
* sizeof(struct RootMemory) == 0x10000000, 256 Mb
  &p->instruction_buffer = 0xc0000000
  &p->outbound_buffer = 0xd0000000
* &p->inbound_buffer = 0xc0000000
which is a bit closer to the correct answer; I believe that the correct
answer should be:
  sizeof(struct RootSection) == 0x10000000, 256 Mb
  sizeof(struct RootMemory) == 0x30000000, 768 Mb
  &p->instruction_buffer = 0xc0000000
  &p->outbound_buffer = 0xd0000000
  &p->inbound_buffer = 0xe0000000

At the very least some warning message could be issued.

sun's native cc, and dec-ultrix cc both topple over with this.


Reading specs from /usr/local/lib/gcc-lib/sparc-sun/2.3.1/specs
gcc version 2.3.1
 /usr/local/lib/gcc-lib/sparc-sun/2.3.1/cpp -lang-c -v -undef -D__GNUC__=2 -Dsparc -Dsun -Dunix -D__sparc__ -D__sun__ -D__unix__ -D__sparc -D__sun -D__unix junk3.c /usr/tmp/cca02979.i
GNU CPP version 2.3.1 (sparc)
 /usr/local/lib/gcc-lib/sparc-sun/2.3.1/cc1 /usr/tmp/cca02979.i -quiet -dumpbase junk3.c -version -o /usr/tmp/cca02979.s
GNU C version 2.3.1 (sparc) compiled by GNU C version 2.3.1.
 /usr/local/lib/gcc-lib/sparc-sun/2.3.1/as -o /usr/tmp/cca029791.o /usr/tmp/cca02979.s
 /usr/local/lib/gcc-lib/sparc-sun/2.3.1/ld -e start -dc -dp /lib/crt0.o -L/usr/local/lib/gcc-lib/sparc-sun/2.3.1 -L/usr/local/lib /usr/tmp/cca029791.o -lgcc -lc -lgcc

#include <stdio.h>
typedef unsigned int u_int;
#define Mb (1024*1024)
struct RootSection {
  u_int data[(128/sizeof(u_int)) * Mb];
  u_int csr[(128/sizeof(u_int)) * Mb];
};
struct RootMemory {
  struct RootSection instruction_buffer;
  struct RootSection outbound_buffer;
  struct RootSection inbound_buffer;
};

#define ROOT_MEMORY_ADDRESS 0xc0000000

main()
{
  struct RootMemory *p = (struct RootMemory *) ROOT_MEMORY_ADDRESS;

  printf("sizeof(struct RootSection) == 0x%08x, %d Mb\n",
    (u_int)sizeof(struct RootSection),
    (u_int)sizeof(struct RootSection)/Mb
  );
  printf("sizeof(struct RootMemory) == 0x%08x, %d Mb\n",
    (u_int)sizeof(struct RootMemory),
    (u_int)sizeof(struct RootMemory)/Mb
  );

  printf("&p->instruction_buffer = 0x%08x\n", &p->instruction_buffer);
  printf("&p->outbound_buffer = 0x%08x\n", &p->outbound_buffer);
  printf("&p->inbound_buffer = 0x%08x\n", &p->inbound_buffer);
}