From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 31739 invoked by alias); 28 Dec 2004 02:33:58 -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 31711 invoked from network); 28 Dec 2004 02:33:51 -0000 Received: from unknown (HELO mail.amplepower.com) (216.39.162.139) by sourceware.org with SMTP; 28 Dec 2004 02:33:51 -0000 Received: from [192.168.8.30] (helo=knuth.amplepower.com ident=roth) by mail.amplepower.com with esmtp (Exim 3.36 #1 (Debian)) id 1Cj7BE-0004mg-00; Mon, 27 Dec 2004 18:33:48 -0800 Date: Tue, 28 Dec 2004 09:10:00 -0000 From: "Theodore A. Roth" X-X-Sender: roth@knuth.amplepower.com cc: Andrew Cagney , gdb-patches@sources.redhat.com Subject: Re: [RFA] initialize err variable in load_section_callback() In-Reply-To: Message-ID: References: <4176A188.1030904@gnu.org> <417D9450.2030401@gnu.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-SW-Source: 2004-12/txt/msg00447.txt.bz2 This patch got left hanging. Is it a lost cause or can I get approval to commit it? Thanks. On Tue, 26 Oct 2004, Theodore A. Roth wrote: > On Mon, 25 Oct 2004, Andrew Cagney wrote: > > > Theodore A. Roth wrote: > > > On Wed, 20 Oct 2004, Andrew Cagney wrote: > > > > > > > > >>Theodore A. Roth wrote: > > >> > > >>>Hi, > > >>> > > >>>I just encountered a problem with using the "load" command with a remote > > >>>avr target. The first packet would be sent to the remote target and then > > >>>gdb would just give up with this error message: > > >>> > > >>> (gdb) load > > >>> Loading section .text, size 0x1f8 lma 0x0 > > >>> Sending packet: $M0,a:0c9446000c9463000c94#d7...Ack > > >>> Packet received: OK > > >>> Memory access error while loading section .text. > > >>> > > >>>It looks like load_section_callback() in symfile.c is assuming that a > > >>>call to target_write_memory_partial() will set the err variable. > > >>>Unfortunately, that is not a valid assumption. > > >>> > > >>>The attached patch got things working again, but this feels like a hack > > >>>to me since target_write_memory_partial() should really be setting err > > >>>to a sane value before returning. > > >>> > > >>>Patch is against today's cvs mainline. > > >> > > >>Here's the contract: > > >>/* Make a single attempt at transfering LEN bytes. On a successful > > >> transfer, the number of bytes actually transfered is returned and > > >> ERR is set to 0. When a transfer fails, -1 is returned (the number > > >> of bytes actually transfered is not defined) and ERR is set to a > > >> non-zero error indication. */ > > >>So the bug is further down the target stack. > > > > > > > > > Both target_write_memory_partial() and target_read_memory_partial() > > > break that contract then: > > > > > > int > > > target_write_memory_partial (CORE_ADDR memaddr, char *buf, int len, int *err) > > > { > > > if (target_xfer_partial_p ()) > > > return target_xfer_partial (target_stack, TARGET_OBJECT_MEMORY, NULL, > > > NULL, buf, memaddr, len); > > > else > > > return target_xfer_memory_partial (memaddr, buf, len, 1, err); > > > } > > > > > > If target_xfer_partial_p() returns true (which the avr port does), then > > > err is never set and the caller will see garbage if it didn't initialize > > > err. > > > > > > Should the return value of the target_xfer_partial() call be checked, or > > > should err just be blindly see to zero? > > > > The result will need to be checked, and *err set accordingly. > > > > Hmm, to_xfer_partial doesn't specify how to handle errors. We'd better > > pin that down. > > > > Of hand the interface could allow: > > > > - when -1, set *err to errno > > Attached patch implements the above case. > > > - when -1, set *err to EIO > > I dug down the stack to see if there was a guarantee if errno is going > to be set if retval -1. I didn't see that so I'm a bit nervous about my > attached patch. Would it make any sense to set errno to 0 before the > call to target_xfer_partial(), then if retval is -1 also check errno? > I.e. if errno == 0, set *err to EIO, else *err to errno. > > > - when -ve, set *err -VE return value > > I assume -ve is an error code? Sould I extend my patch to also check for > retval < -1 and if so set *err to retval? > > > > > I suspect that it should be the first. The comments for > > target_read_partial should also be updated to mention this. > > You lost me on this one. target_read_partial() with comments currently > reads like this: > > /* Target vector read/write partial wrapper functions. > > NOTE: cagney/2003-10-21: I wonder if having "to_xfer_partial > (inbuf, outbuf)", instead of separate read/write methods, make life > easier. */ > > LONGEST > target_read_partial (struct target_ops *ops, > enum target_object object, > const char *annex, void *buf, > ULONGEST offset, LONGEST len) > { > return target_xfer_partial (ops, object, annex, buf, NULL, offset, len); > } > > Was there some other comment you had in mind? > > Thanks for helping me with this. > > --- > Ted Roth > PGP Key ID: 0x18F846E9 > Jabber ID: troth@jabber.org --- Ted Roth PGP Key ID: 0x18F846E9 Jabber ID: troth@jabber.org