🚀 go-pugleaf

I hesitate to report this as a bug, because some might well consider
it a feature...

The problem occurs with gdb 4.6, compiled with gcc 2.2.2 on a sun4
host.

It seems the sun requires doubles to be aligned to 8-byte boundaries,
violations result in bus errors.  That's fine, except that gdb allows
me to do unaligned accesses with the p command.  I was porting some
code from a decstation to a sun, and got very confused when I could
write to pointers from within gdb, but my program couldn't.
It would be nice if gdb warned me when it did an unaligned access.

I've appended a simple example program below.

				- Fritz


/* Illustrate funny byte alignment problem with gdb
 *
 *  F. Herrmann  fritz@mtl.mit.edu
 *
 */

int main( int argc, char **argv)
{
  double dblarray[2];
  double *goodptr, *badptr;

  /* Start with a good pointer to a double */

  goodptr = dblarray;

  /* Create an unaligned bad pointer */

  badptr = (double *) ( 1 + (int *) goodptr);

  /* Put a break point here.
   *
   *  The unaligned assignment below will cause a bus error on a sun.
   *  But GDB is perfectly happy to let you do:
   *
   *	 (gdb) p *badptr
   *
   *  or even:
   *
   *     (gdb) p *badptr = 2.718
   *
   *  I guess it's nice that gdb can do something the hardware can't, but
   *  I would have appreciated a warning that the operation was illegal.
   *  I was porting some code from a decstation to a sun and got stuck on
   *  this for some time.
   */

  /* Try to store a double */

  *badptr = 3.14159;

  /* Don't expect to get here */

  printf( "%f\n", *badptr);

  return 0;
}