Re: gdb_assert will never be triggered

Andrew Cagney
2004-07-29T22:56:57Z

>>>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:

(catching up with the backlog)

Right. PREV_FRAME should never be NULL. Unfortunatly breakage
elsewhere means that it occasionally is :-( If we fix the breakage we
can delete that if() and then the assert will make sense :-)

Andrew

> /* 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