From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 4589 invoked by alias); 22 Jul 2004 03:25:00 -0000 Mailing-List: contact gdb-patches-help@sources.redhat.com; run by ezmlm Precedence: bulk List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sources.redhat.com Received: (qmail 4582 invoked from network); 22 Jul 2004 03:24:59 -0000 Received: from unknown (HELO takamaka.act-europe.fr) (142.179.108.108) by sourceware.org with SMTP; 22 Jul 2004 03:24:59 -0000 Received: by takamaka.act-europe.fr (Postfix, from userid 507) id B0E2347D91; Wed, 21 Jul 2004 20:24:58 -0700 (PDT) Date: Thu, 22 Jul 2004 03:25:00 -0000 From: Joel Brobecker To: Andrew Cagney Cc: gdb-patches@sources.redhat.com Subject: Re: gdb_assert will never be triggered Message-ID: <20040722032458.GW1278@gnat.com> References: <20040722023907.GV1278@gnat.com> <40FF325F.6030207@gnu.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <40FF325F.6030207@gnu.org> User-Agent: Mutt/1.4i X-SW-Source: 2004-07/txt/msg00307.txt.bz2 > >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