Re: gdb_assert will never be triggered

Joel Brobecker
2004-07-22T03:25:00Z

> >It looks like the assertion will always be true, due to the block
> >above... Do we want to keep this gdb_assert() call nonetheless?
>
> Yes. Can you post the snipped comments (both of them :-).

Here is everything:

<<
/* Return the inner-most frame, when the caller passes in NULL. */
/* NOTE: cagney/2002-11-09: Not sure how this would happen. The
caller should have previously obtained a valid frame using
get_selected_frame() and then called this code - only possibility
I can think of is code behaving badly.

NOTE: cagney/2003-01-10: Talk about code behaving badly. Check
block_innermost_frame(). It does the sequence: frame = NULL;
while (1) { frame = get_prev_frame (frame); .... }. Ulgh! Why
it couldn't be written better, I don't know.

NOTE: cagney/2003-01-11: I suspect what is happening in
block_innermost_frame() is, when the target has no state
(registers, memory, ...), it is still calling this function. The
assumption being that this function will return NULL indicating
that a frame isn't possible, rather than checking that the target
has state and then calling get_current_frame() and
get_prev_frame(). This is a guess mind. */
if (this_frame == NULL)
{
/* NOTE: cagney/2002-11-09: There was a code segment here that
would error out when CURRENT_FRAME was NULL. The comment
that went with it made the claim ...

``This screws value_of_variable, which just wants a nice
clean NULL return from block_innermost_frame if there are no
frames. I don't think I've ever seen this message happen
otherwise. And returning NULL here is a perfectly legitimate
thing to do.''

Per the above, this code shouldn't even be called with a NULL
THIS_FRAME. */
frame_debug_got_null_frame (gdb_stdlog, this_frame, "this_frame NULL");
return current_frame;
}

/* There is always a frame. If this assertion fails, suspect that
something should be calling get_selected_frame() or
get_current_frame(). */
gdb_assert (this_frame != NULL);
>>

--
Joel