From owner-freebsd-bugs Mon Dec 11 9:40:13 2000 From owner-freebsd-bugs@FreeBSD.ORG Mon Dec 11 09:40:01 2000 Return-Path: Delivered-To: freebsd-bugs@hub.freebsd.org Received: from freefall.freebsd.org (freefall.FreeBSD.org [216.136.204.21]) by hub.freebsd.org (Postfix) with ESMTP id A06B437B402 for ; Mon, 11 Dec 2000 09:40:01 -0800 (PST) Received: (from gnats@localhost) by freefall.freebsd.org (8.11.1/8.11.1) id eBBHe1m40780; Mon, 11 Dec 2000 09:40:01 -0800 (PST) (envelope-from gnats) Resent-Date: Mon, 11 Dec 2000 09:40:01 -0800 (PST) Resent-Message-Id: <200012111740.eBBHe1m40780@freefall.freebsd.org> Resent-From: gnats-admin@FreeBSD.org (GNATS Management) Resent-To: freebsd-bugs@FreeBSD.org Resent-Reply-To: gnats-admin@FreeBSD.org, Peter Pentchev Received: from ringworld.nanolink.com (pool249-tch-1.Sofia.0rbitel.net [212.95.170.249]) by hub.freebsd.org (Postfix) with SMTP id 7F67D37B400 for ; Mon, 11 Dec 2000 09:30:07 -0800 (PST) Received: (qmail 4382 invoked by uid 1000); 11 Dec 2000 17:29:16 -0000 Message-Id: <20001211172916.4381.qmail@ringworld.nanolink.com> Date: 11 Dec 2000 17:29:16 -0000 From: Peter Pentchev Reply-To: Peter Pentchev To: FreeBSD-gnats-submit@freebsd.org X-Send-Pr-Version: 3.2 Subject: bin/23472: gdb weirdness on programs compiled with -ggdb Resent-Sender: gnats@FreeBSD.org Sender: owner-freebsd-bugs@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org >Number: 23472 >Category: bin >Synopsis: gdb weirdness on programs compiled with -ggdb >Confidential: no >Severity: non-critical >Priority: low >Responsible: freebsd-bugs >State: open >Quarter: >Keywords: >Date-Required: >Class: sw-bug >Submitter-Id: current-users >Arrival-Date: Mon Dec 11 09:40:00 PST 2000 >Closed-Date: >Last-Modified: >Originator: Peter Pentchev >Release: FreeBSD 4.2-STABLE i386 >Organization: Orbitel JSCo. >Environment: FreeBSD FreeBSD 4.2-STABLE #6: Mon Dec 11 12:57:38 EET 2000 root@ringworld.oblivion.bg:/usr/obj/usr/src/sys/RINGWORLD >Description: If a program is compiled with -ggdb, gdb sometimes loses track of local variables' addresses and/or contents. >How-To-Repeat: Consider the following program: #include #include #define BUFLEN 100 int readstring(char *s, int len) { printf("readstring(%p, %d) called, s='%s'\n", s, len, s); return 0; } int main(void) { char str[BUFLEN] = "string"; printf("in main: str=%p, sizeof(str)=%d, str='%s'\n", str, sizeof(str), str); readstring(str, sizeof(str)); return 0; } ..and the following Makefile: CFLAGS = -g3 -ggdb all: zettest clean: rm -f zettest Following is the transcript of a gdb session. Script started on Mon Dec 11 17:48:52 2000 [roam@ringwraith ~/c/misc/zettest]$ gdb zettest GNU gdb 4.18 Copyright 1998 Free Software Foundation, Inc. GDB is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions. Type "show copying" to see the conditions. There is absolutely no warranty for GDB. Type "show warranty" for details. This GDB was configured as "i386-unknown-freebsd"... (gdb) br main Breakpoint 1 at 0x8048572: file zettest.c, line 15. (gdb) r Starting program: /usr/home/roam/lang/c/misc/zettest/zettest Breakpoint 1, main () at zettest.c:15 15 char str[BUFLEN] = "string"; (gdb) n 17 printf("in main: str=%p, sizeof(str)=%d, str='%s'\n", str, sizeof(str), str); (gdb) in main: str=0xbfbff904, sizeof(str)=100, str='string' ^^^^^^^^^^ real address ^^^^^^^^ real contents 18 readstring(str, sizeof(str)); (gdb) print (void *) str $1 = (void *) 0xbfbff88c ^^^^^^^^^^ something's fishy.. (gdb) print &str[0] $2 = 0xbfbff88c "" (gdb) s readstring (s=0xbfbff968 "´ù¿¿\211\204\004\b\001", len=134514114) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ uhm ^^^^^^^^^ excuse me?! at zettest.c:9 9 printf("readstring(%p, %d) called, s='%s'\n", s, len, s); (gdb) n readstring(0xbfbff904, 100) called, s='string' ^^^^^^^^^^ ^^^ ^^^^^^ everyhing's just fine 10 return 0; (gdb) c Continuing. Program exited normally. (gdb) quit [roam@ringwraith ~/c/misc/zettest]$ exit exit Script done on Mon Dec 11 17:49:15 2000 Well, so.. the program executed correctly, the addresses and values as printed by the printf() in readstring() were perfectly OK. Just gdb showed something wrong - in a program compiled with additional info for the purpose of debugging with gdb :) Here's the 'ident gdb' output.. /usr/bin/gdb: $FreeBSD: src/lib/libc/i386/string/strrchr.S,v 1.5 1999/08/27 23:59:35 peter Exp $ $FreeBSD: src/lib/libc/i386/string/strncmp.S,v 1.6 1999/08/27 23:59:35 peter Exp $ $FreeBSD: src/lib/libc/i386/string/index.S,v 1.5 1999/08/27 23:59:30 peter Exp $ $FreeBSD: src/lib/libc/i386/string/strcpy.S,v 1.5 1999/08/27 23:59:34 peter Exp $ $FreeBSD: src/lib/libc/i386/string/strcmp.S,v 1.5 1999/08/27 23:59:33 peter Exp $ $FreeBSD: src/lib/libc/i386/string/memchr.S,v 1.8 1999/08/27 23:59:31 peter Exp $ $NetBSD: bcopy.S,v 1.6 1996/11/12 00:50:06 jtc Exp $ $FreeBSD: src/lib/libc/i386/string/memset.S,v 1.5 1999/08/27 23:59:32 peter Exp $ $NetBSD: bcopy.S,v 1.6 1996/11/12 00:50:06 jtc Exp $ $FreeBSD: src/lib/libc/i386/sys/brk.S,v 1.7 1999/08/27 23:59:38 peter Exp $ $FreeBSD: src/lib/libc/i386/sys/sbrk.S,v 1.7 1999/08/27 23:59:44 peter Exp $ $FreeBSD: src/lib/libc/i386/sys/cerror.S,v 1.10 1999/08/27 23:59:38 peter Exp $ $FreeBSD: src/lib/libc/gen/err.c,v 1.6 1999/08/27 23:58:33 peter Exp $ $FreeBSD: src/lib/libc/i386/gen/isinf.c,v 1.6 1999/08/27 23:59:21 peter Exp $ $FreeBSD: src/lib/libc/stdio/asprintf.c,v 1.6 1999/08/28 00:00:55 peter Exp $ I do not know which FreeBSD releases are affected by this - I only have very recent 4.2-STABLE and -current machines :( And freefall was updated to a very-very recent 4.2-STABLE just hours before I needed to test :) >Fix: Wish I knew :( A friend wasted hours today in a gdb session, thinking his program was passing a value of 100 as 134 millions.. and at the same time marvelling at the program's perfectly fine output :( >Release-Note: >Audit-Trail: >Unformatted: To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-bugs" in the body of the message