From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 14615 invoked by alias); 6 Jul 2011 01:29:52 -0000 Received: (qmail 14591 invoked by uid 22791); 6 Jul 2011 01:29:52 -0000 X-SWARE-Spam-Status: No, hits=-2.8 required=5.0 tests=ALL_TRUSTED,AWL,BAYES_00 X-Spam-Check-By: sourceware.org Received: from localhost (HELO sourceware.org) (127.0.0.1) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Wed, 06 Jul 2011 01:29:40 +0000 From: "qiyao at gcc dot gnu.org" To: gdb-prs@sourceware.org Subject: [Bug gdb/12956] Watchpoint on invalid memory addressed is too slow, they should be 'pending' until allocated X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gdb X-Bugzilla-Component: gdb X-Bugzilla-Keywords: X-Bugzilla-Severity: enhancement X-Bugzilla-Who: qiyao at gcc dot gnu.org X-Bugzilla-Status: NEW X-Bugzilla-Priority: P2 X-Bugzilla-Assigned-To: unassigned at sourceware dot org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Changed-Fields: CC Message-ID: In-Reply-To: References: X-Bugzilla-URL: http://sourceware.org/bugzilla/ Auto-Submitted: auto-generated Content-Type: text/plain; charset="UTF-8" MIME-Version: 1.0 Date: Wed, 06 Jul 2011 01:29:00 -0000 Mailing-List: contact gdb-prs-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-prs-owner@sourceware.org X-SW-Source: 2011-q3/txt/msg00023.txt.bz2 http://sourceware.org/bugzilla/show_bug.cgi?id=12956 Yao Qi changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |qiyao at gcc dot gnu.org --- Comment #1 from Yao Qi 2011-07-06 01:29:22 UTC --- (In reply to comment #0) > I am setting a watchpoint for the memory address that is not yet allocated. I > am interested in what happens when it is allocated and later. > > 'watch' statement sets a software watchpoint, and program instantly becomes > very slow. My guess is that gdb traces the program and checks if the memory is > valid after each instruction. This is wrong. > yes, in software watchpoint, gdb will execute program in a single step manner, and check memory changed or not. That is why program is slow, but I don't think it is wrong. > Since memory can only become valid after mmap or brk/sbrk calls, gdb should > only trace those calls in such situation, which is a 'pending' state for a > watchpoint. Once the memory address becomes valid, gdb should change status to > hardware watchpoint. If the memory is deallocated again (with munmap or ^^^^^^^^^^^^^^^^^^^ I guess you mean "software watchpoint" here. > brk/sbrk calls) gdb should change state back to 'pending' and wait for the > possible other allocations. This approach you proposed should speed up watchpoint in some cases. GDB also supports debugging ELF without OS on some bare-mental boards, so syscall mmap/brk/sbrk/ is not available there. -- Configure bugmail: http://sourceware.org/bugzilla/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are on the CC list for the bug.