From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 22216 invoked by alias); 20 Feb 2004 21:27:47 -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 22206 invoked from network); 20 Feb 2004 21:27:44 -0000 Received: from unknown (HELO localhost.redhat.com) (216.129.200.20) by sources.redhat.com with SMTP; 20 Feb 2004 21:27:44 -0000 Received: from gnu.org (localhost [127.0.0.1]) by localhost.redhat.com (Postfix) with ESMTP id AFC1F2B92; Fri, 20 Feb 2004 16:27:41 -0500 (EST) Message-ID: <40367BCD.8090403@gnu.org> Date: Fri, 20 Feb 2004 21:27:00 -0000 From: Andrew Cagney User-Agent: Mozilla/5.0 (X11; U; NetBSD macppc; en-US; rv:1.4.1) Gecko/20040217 MIME-Version: 1.0 To: gdb-patches@sources.redhat.com Subject: [patch/rfc] The off again, on again, PC == 0 in get_prev_frame Content-Type: multipart/mixed; boundary="------------040700090607040506090609" X-SW-Source: 2004-02/txt/msg00567.txt.bz2 This is a multi-part message in MIME format. --------------040700090607040506090609 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Content-length: 1649 Ref: [PATCH] Don't try to unwind the PC in frame.c:get_prev_frame() http://sources.redhat.com/ml/gdb-patches/2004-01/msg00104.html Having only recently posted: > Can just you add a -ve comment stating why a test for PC==0 does not belong in that function? I'm pretty much certain that someone will eventually try to re-add a very similar test (via inside_entry_func for instance). the attached adds a conditionalized check for "PC == 0" to get_prev_frame. If there's a zero PC, _and_ it isn't the inner most frame, stop unwinding. That should let mark's original case through. Turns out that the old removed test was stopping this problem on amd64: (gdb) PASS: gdb.threads/linux-dp.exp: continue to breakpoint: thread 5's print where #0 print_philosopher (n=3, left=33 '!', right=33 '!') at /home/cygnus/cagney/GD B/src/gdb/testsuite/gdb.threads/linux-dp.c:105 #1 0x0000000000400e4a in philosopher (data=0x50177c) at /home/cygnus/cagney/GDB /src/gdb/testsuite/gdb.threads/linux-dp.c:148 #2 0x0000002a95671c2b in start_thread () from /lib64/tls/libpthread.so.0 #3 0x0000002a959de040 in thread_start () from /lib64/tls/libc.so.6 #4 0x0000000000000000 in ?? () #5 0x0000000000000000 in ?? () #6 0x0000000000000000 in ?? () #7 0x0000000000000000 in ?? () #8 0x0000000000000000 in ?? () #9 0x0000000000000000 in ?? () #10 0x0000000000000000 in ?? () #11 0x0000000000000000 in ?? () #12 0x0000000000000000 in ?? () #13 0x0000000000000000 in ?? () #14 0x0000000000000000 in ?? () #15 0x0000000000000000 in ?? () #16 0x0000002a95b41580 in _nl_C_locobj () from /lib64/tls/libc.so.6 #17 0x00000000427ffdc8 in ?? () comments (...) Andrew --------------040700090607040506090609 Content-Type: text/plain; name="diffs" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="diffs" Content-length: 1955 2004-02-20 Andrew Cagney * frame.c (get_prev_frame): With the exception of the inner-most frame, do not backtrace past a frame with a zero pc. Index: frame.c =================================================================== RCS file: /cvs/src/src/gdb/frame.c,v retrieving revision 1.162 diff -u -r1.162 frame.c --- frame.c 16 Feb 2004 21:49:21 -0000 1.162 +++ frame.c 20 Feb 2004 21:12:52 -0000 @@ -1721,14 +1721,9 @@ return prev; } -/* Return a structure containing various interesting information - about the frame that called THIS_FRAME. Returns NULL - if there is no such frame. - - This function tests some target-independent conditions that should - terminate the frame chain, such as unwinding past main(). It - should not contain any target-dependent tests, such as checking - whether the program-counter is zero. */ +/* Return a structure containing various interesting information about + the frame that called THIS_FRAME. Returns NULL if there is no such + frame. */ struct frame_info * get_prev_frame (struct frame_info *this_frame) @@ -1843,6 +1838,24 @@ fprint_frame (gdb_stdlog, NULL); fprintf_unfiltered (gdb_stdlog, "// inside entry func }\n"); } + return NULL; + } + + /* Don't allow frames with a zero PC to unwind. The exception is + the inner-most frame - a jump through a NULL pointer results in + an inner most frame that is both unwindable and has a zero + PC. */ + /* NOTE: cagney/2004-02-20: The old zero PC check, removed + 2004-01-11, had the problem that it stopped backtraces from that + inner most zero PCed frame. */ + if (this_frame->level > 0 && get_frame_pc (this_frame) == 0) + { + if (frame_debug) + { + fprintf_unfiltered (gdb_stdlog, "-> "); + fprint_frame (gdb_stdlog, NULL); + fprintf_unfiltered (gdb_stdlog, " // PC zero }\n"); + } return NULL; } --------------040700090607040506090609--