From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 19533 invoked by alias); 24 Sep 2003 19:31:45 -0000 Mailing-List: contact gdb-help@sources.redhat.com; run by ezmlm Precedence: bulk List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-owner@sources.redhat.com Received: (qmail 19493 invoked from network); 24 Sep 2003 19:31:44 -0000 Received: from unknown (HELO mx1.redhat.com) (66.187.233.31) by sources.redhat.com with SMTP; 24 Sep 2003 19:31:44 -0000 Received: from int-mx1.corp.redhat.com (int-mx1.corp.redhat.com [172.16.52.254]) by mx1.redhat.com (8.11.6/8.11.6) with ESMTP id h8OJVg128297 for ; Wed, 24 Sep 2003 15:31:43 -0400 Received: from pobox.corp.redhat.com (pobox.corp.redhat.com [172.16.52.156]) by int-mx1.corp.redhat.com (8.11.6/8.11.6) with ESMTP id h8OJVgc06994 for ; Wed, 24 Sep 2003 15:31:42 -0400 Received: from localhost.redhat.com (devserv.devel.redhat.com [172.16.58.1]) by pobox.corp.redhat.com (8.12.8/8.12.8) with ESMTP id h8OJVfeX031667; Wed, 24 Sep 2003 15:31:41 -0400 Received: by localhost.redhat.com (Postfix, from userid 469) id 348EE2CC8D; Wed, 24 Sep 2003 15:41:24 -0400 (EDT) From: Elena Zannoni MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <16241.62308.13394.591111@localhost.redhat.com> Date: Wed, 24 Sep 2003 19:31:00 -0000 To: Andrew Haley Cc: gcc@gcc.gnu.org, gdb@sources.redhat.com Subject: Re: Handling aliases in debug information In-Reply-To: <200309241445.h8OEjLJt011370@cuddles.cambridge.redhat.com> References: <200309241445.h8OEjLJt011370@cuddles.cambridge.redhat.com> X-SW-Source: 2003-09/txt/msg00304.txt.bz2 Andrew Haley writes: > In this program, a and b are aliases for the same variable: > > int > main (int argc, char *argv[]) > { > union > { > int a; > int b; > }; > a = argc; > return b; > } > > But debugging is hard: > > cuddles:~ $ g++ -v > Reading specs from /usr/local/lib/gcc/i686-pc-linux-gnu/3.4/specs > Configured with: '/local/aph/gcc/gcc/configure' '--enable-threads=posix '--enable-languages=c,c++,java : (reconfigured) > Thread model: posix > gcc version 3.4 20030915 (experimental) > cuddles:~ $ g++ union.cc -g > cuddles:~ $ gdb ./a.out > GNU gdb 5.2.1 > Copyright 2002 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 "i686-pc-linux-gnu"... > (gdb) b main > Breakpoint 1 at 0x8048434: file union.cc, line 10. > (gdb) r > Starting program: /cuddles/aph/home/a.out > > Breakpoint 1, main (argc=1, argv=0xbfffdbc4) at union.cc:10 > 10 a = argc; > (gdb) n > 11 return b; > (gdb) p a > No symbol "a" in current context. > (gdb) info locals > No locals. > > Is this because > > a. g++ is not generating good debug info for anonymous unions? > b. gdb is not interpreting g++ debug info correctly? > c. Some other reason? Hmm, I do not see this: [ezannoni@topanga ezannoni]$ gcc -g aph.cc -o aph [ezannoni@topanga ezannoni]$ gdb ./aph GNU gdb Red Hat Linux (5.3.90-0.20030710.39rh) Copyright 2003 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-redhat-linux-gnu"...Using host libthread_db library "/lib/tls/libthread_db.so.1". (gdb) b main Breakpoint 1 at 0x8048324: file aph.cc, line 9. (gdb) r Starting program: /home/ezannoni/aph Breakpoint 1, main (argc=1, argv=0xbfffc5b4) at aph.cc:9 9 a = argc; (gdb) p a $1 = 134513528 (gdb) p b $2 = 134513528 (gdb) info locals a = 134513528 b = 134513528 (gdb) n 10 return b; (gdb) info locals a = 1 b = 1 (gdb) [ezannoni@topanga ezannoni]$ gcc -v Reading specs from /usr/lib/gcc-lib/i386-redhat-linux/3.2.3/specs Configured with: ../configure --prefix=/usr --mandir=/usr/share/man --infodir=/usr/share/info --enable-shared --enable-threads=posix --disable-checking --with-system-zlib --enable-__cxa_atexit --host=i386-redhat-linux Thread model: posix gcc version 3.2.3 20030502 (Red Hat Linux 3.2.3-20) But I see you are using an ancient gdb. So maybe try a newer one. elena