Re: [PATCH] Compare contents when evaluating an array watchpoint

[Klee Dienes <klee at apple dot com>]

Sure:  breakpoint.c:984 (in insert_breakpoints), and breakpoint.c:5480 
(in can_use_hardware_watchpoint).

Here's the relevant code from breakpoint.c:984:

            /* Look at each value on the value chain.  */
            for (; v; v = v->next)
              {
                /* If it's a memory location, and GDB actually needed
                   its contents to evaluate the expression, then we
                   must watch it.  */
                if (VALUE_LVAL (v) == lval_memory
                    && ! VALUE_LAZY (v))
                  {
                    struct type *vtype = check_typedef (VALUE_TYPE (v));

                    /* We only watch structs and arrays if user asked
                       for it explicitly, never if they just happen to
                       appear in the middle of some value chain.  */
                    if (v == b->val_chain
                        || (TYPE_CODE (vtype) != TYPE_CODE_STRUCT
                            && TYPE_CODE (vtype) != TYPE_CODE_ARRAY))
                      {
                        CORE_ADDR addr;
                        int len, type;

                        addr = VALUE_ADDRESS (v) + VALUE_OFFSET (v);
                        len = TYPE_LENGTH (VALUE_TYPE (v));
                        type = hw_write;
                        if (b->type == bp_read_watchpoint)
                          type = hw_read;
                        else if (b->type == bp_access_watchpoint)
                          type = hw_access;

                        val = target_insert_watchpoint (addr, len, 
type);

On Monday, October 7, 2002, at 10:26 AM, Eli Zaretskii wrote:

> On Mon, 7 Oct 2002, Klee Dienes wrote:
>
> > My patch doesn't change the behavior
> > of the trigger phase at all --- this phase has always set the trigger
> > to watch the entire contents of the array.
> IIRC, that's not true: what you call ``the trigger phase'' was watching
> the address of the array, not its contents.  To watch the contents, you
> needed to watch specific array elements.
>
> In other words, "watch my_array" would break when the pointer to
> the first element of my_array[] changed to point to a different memory
> location.  If you want to watch array contents, you need to say
> "watch my_array[0]", "watch my_array[1]", etc.
>
> Of course, it's been a while since I looked at that code, so I might be
> mistaken.  If so, could you please tell where's the code in the current
> CVS sources which is watching the entire contents of the array?