Debian bug report logs - #660, boring messages

Message sent to debian-devel@pixar.com:


Subject: Bug#660: GDB gets address of structure member wrong in memory breakpoint
Reply-To: iwj10@cus.cam.ac.uk (Ian Jackson), debian-bugs@pixar.com
Resent-To: debian-devel@pixar.com
Resent-From: iwj10@cus.cam.ac.uk (Ian Jackson)
Resent-Sender: iwj10@cus.cam.ac.uk
Resent-Date: Mon, 27 Mar 1995 15:33:04 GMT
Resent-Message-ID: <debian-bugs-handler.660.03271520383803@pixar.com>
X-Debian-PR-Package: gdb
X-Debian-PR-Keywords: 
Received: via spool for debian-bugs; Mon, 27 Mar 1995 15:33:04 GMT
Received: with rfc822 via encapsulated-mail id 03271520383803;
          Mon, 27 Mar 1995 15:20:40 GMT
Received: from pixar.com by mongo.pixar.com with smtp
	(Smail3.1.28.1 #15) id m0rtGVT-0006USC; Mon, 27 Mar 95 07:15 PST
Received: from bootes.cus.cam.ac.uk by pixar.com with SMTP id AA14255
  (5.65c/IDA-1.4.4 for <debian-bugs@pixar.com>); Mon, 27 Mar 1995 07:09:41 -0800
Received: by bootes.cus.cam.ac.uk
	(Smail-3.1.29.0 #30) id m0rtFaj-000BzvC; Mon, 27 Mar 95 15:16 BST
Received: by chiark (Smail3.1.28.1 #3)
	id m0rtE8u-0002gOZ; Mon, 27 Mar 95 13:43 BST
Message-Id: <m0rtE8u-0002gOZ.ijackson@nyx.cs.du.edu>
Date: Mon, 27 Mar 95 13:43 BST
From: iwj10@cus.cam.ac.uk (Ian Jackson)
To: Debian bugs submission address <debian-bugs@pixar.com>

Package: gdb
Version: 4.12

As you can see below, when setting a memory breakpoint on a structure
member GDB uses the address of the start of the structure by mistake.
Applying *& to the member (to take its address and then dereference
it) gives correct results.

chiark:~/junk> cat t.c
struct foo { int a,b; };

void fong(struct foo *p, int x) { p->b=x; }

int main(int argc, char **argv) {
  struct foo f;
  f.a= 2;
  f.b= 3;
  fong(&f,4);
  f.b=5;
  fong(&f,6);
}
chiark:~/junk> gcc -g t.c
chiark:~/junk> /new/usr/bin/gdb a.out
GDB is free software and you are welcome to 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.
GDB 4.12 (i486-debian-linux), Copyright 1994 Free Software Foundation, Inc...
(gdb) break main
Breakpoint 1 at 0x6f: file t.c, line 7.
(gdb) run
Starting program: /u/ian/junk/a.out

Breakpoint 1, main (argc=1, argv=0xbffff978) at t.c:7
7         f.a= 2;
(gdb) step
8         f.b= 3;
(gdb) step
9         fong(&f,4);
(gdb) print f
$1 = {a = 2, b = 3}
(gdb) abreak f.b
Memorypoint 2: f.b
(gdb) abreak f.a
Memorypoint 3: f.a
(gdb) abreak *&f.b
Memorypoint 4: *&f.b
(gdb) info memory
Num Type           Disp Enb Address    What
2   memorypoint    keep y   0xbffff95c  r/w  4   f.b
3   memorypoint    keep y   0xbffff95c  r/w  4   f.a
4   memorypoint    keep y   0xbffff960  r/w  4   *&f.b
(gdb) cont
Continuing.

Memory breakpoint 4 on *&f.b at 0xbffff960 with length 4: accessed.
3       void fong(struct foo *p, int x) { p->b=x; }
(gdb) disable 4
(gdb) cont
Continuing.

Memory breakpoint 2 on f.b at 0xbffff95c with length 4: accessed.
0x224   exit.c:38: No such file or directory.
(gdb) where
#0  0x224 in exit (status=-1073743524) at exit.c:38
(gdb) quit
The program is running.  Quit anyway (and kill it)? (y or n) y
chiark:~/junk> gcc -v
Reading specs from /usr/lib/gcc-lib/i486-linux/2.5.8/specs
gcc version 2.5.8
chiark:~/junk> gcc -c -g t.c
chiark:~/junk> nm -a t.o
00000000 - 00 0003 SLINE
00000003 - 00 0003 SLINE
0000000c - 00 0003 SLINE
00000010 - 00 0005 SLINE
0000001b - 00 0006 SLINE
0000001b - 00 0007 SLINE
00000022 - 00 0008 SLINE
00000029 - 00 0009 SLINE
00000037 - 00 000a SLINE
0000003e - 00 000b SLINE
0000004c - 00 000c SLINE
0000004c - 00 000c SLINE
0000001b - 00 0000 LBRAC
0000004c - 00 0000 RBRAC
00000000 - 00 0000    SO /u/ian/junk/
00000000 t ___gnu_compiled_c
         U ___main
00000000 T _fong
00000010 T _main
00000008 - 00 0005  PSYM argc:p1
0000000c - 00 0005  PSYM argv:p22=*23=*2
00000000 - 00 0000  LSYM char:t2=r2;0;127;
00000000 - 00 0000  LSYM complex double:t17=r17;8;0;
00000000 - 00 0000  LSYM complex float:t16=r16;4;0;
00000000 - 00 0000  LSYM complex int:t15=s8real:1,0,32;imag:1,32,32;;
00000000 - 00 0000  LSYM complex long double:t18=r18;12;0;
00000000 - 00 0000  LSYM double:t13=r1;8;0;
fffffff8 - 00 0006  LSYM f:20
00000000 - 00 0000  LSYM float:t12=r1;4;0;
00000000 - 00 0003   FUN fong:F19
00000000 - 00 0000  LSYM foo:T20=s8a:1,0,32;b:1,32,32;;
00000000 t gcc2_compiled.
00000000 - 00 0000  LSYM int:t1=r1;-2147483648;2147483647;
00000000 - 00 0000  LSYM long double:t14=r1;12;0;
00000000 - 00 0000  LSYM long int:t3=r1;-2147483648;2147483647;
00000000 - 00 0000  LSYM long long int:t6=r1;01000000000000000000000;0777777777777777777777;
00000000 - 00 0000  LSYM long long unsigned int:t7=r1;0000000000000;01777777777777777777777;
00000000 - 00 0000  LSYM long unsigned int:t5=r1;0;-1;
00000010 - 00 0005   FUN main:F1
00000008 - 00 0003  PSYM p:p21=*20
00000000 - 00 0000  LSYM short int:t8=r1;-32768;32767;
00000000 - 00 0000  LSYM short unsigned int:t9=r1;0;65535;
00000000 - 00 0000  LSYM signed char:t10=r1;-128;127;
00000000 - 00 0000    SO t.c
00000000 - 00 0000  LSYM unsigned char:t11=r1;0;255;
00000000 - 00 0000  LSYM unsigned int:t4=r1;0;-1;
00000000 - 00 0000  LSYM void:t19=19
0000000c - 00 0003  PSYM x:p1
chiark:~/junk> gzip -9 <t.o | uuencode t.o
begin 664 t.o
M'XL(`$>Q=B\"`WV2/6S30!3'7YJD2=L@(75@8`$$`ZAM?.<D=FP%,1`F)#)0
MB059KO-1IXX=Y:/JB-0IJBK!R,:,Q`P30@(I(+&PL,#`0*4.$1-#!J3P[LYQ
MSE7!DOU^_K]/OW,F48<:+*X[2\)FP_?MT<E1-7NTG1O54J/)X_?X?CC)GI[,
M9K-Q=<J"Q]4_233MU'%U6CO]C([##UD4TTQ<YN)K(;+\2ZA>!;B00IL*>ZQ+
M?`/O>LA4XA+>3T)^)'%;XF<2OY3XH\2YQ()K$OL2/Y7XE<2?)/XF\2^),TL+
M+DC\0.(]B8\E?B[Q&^2T="YW(1GCI,0YM&\Q_GJHCI%?(+,S_!(RB_D:UKP8
MY:8Y?T<]$>NU#)<CSDB<A6L1K\#-B%=!BW@-;D><@_MG^">?4_2=\-G2?,[?
M(;,Y4TFVAV68XF^S@OP.-3;#*O(/M*S.&G++<:CE!)VNZS7J6V!95LL?1H+E
M0'Z8=VT_WQ[Z>WD8;#G@^@-C0"H]8FY24M`*NEHJZ&:$F@G.KMTS!K32HZ9B
M$HJ*%_BM*SQ1_5_BT.^[+;]1%Z$%%JJ8FR3,CWN+9[R+%B7N(<IYEZEHYUUR
MC7@;C1>+ER#_J-'?#7H#D:;SSU2I5M)-]HR\\>IE\1&E8E$M8H3PB/41A9<@
M5!<KC!)#-Q&IM(B)32^PV:%0IA50A7HPW/$:*/%]ZTSB'Q?I?+F$'1"PP_8:
M!V(B4JST]5[#]@RRH6RHU'0[=@M9I>QE$3QOR99=$CWGKJ@'VYTFFL]]\2'8
MEO1PBOW`K:-4KI`R-(/`>$@5G,2>C[$CS6`UL0JPAW$/H[M&EY+*+:K`@=$E
F8'5LUV<_,K?L@5%@]UH.\Z+=QWB*\2K>T#0P#^`OH--.$L,%``#*
`
end

Message sent:


From: iwj10@thor.cam.ac.uk (Ian Jackson)
To: iwj10@cus.cam.ac.uk (Ian Jackson)
Subject: Bug#660: Acknowledgement (was: GDB gets address of structure member wrong in memory breakpoint)
In-Reply-To: <m0rtE8u-0002gOZ.ijackson@nyx.cs.du.edu>
References: <m0rtE8u-0002gOZ.ijackson@nyx.cs.du.edu>

Thank you for the problem report you have sent regarding Debian GNU/Linux.
This is an automatically generated reply, to let you know your message has
been received.  It is being forwarded to the developers' mailing list for
their attention; they will reply in due course.

If you wish to submit further information on your problem, please send
it to debian-bugs@pixar.com, but please ensure that the Subject
line of your message starts with "Bug#660" or "Re: Bug#660" so that
we can identify it as relating to the same problem.

Please do not reply to the address at the top of this message,
unless you wish to report a problem with the bug-tracking system.

Ian Jackson
(maintainer, debian-bugs)

Message sent to debian-devel@pixar.com:


Subject: Bug#660: GDB gets address of structure member wrong in memory breakpoint
Reply-To: Ian Jackson <ian@chiark.chu.cam.ac.uk>, debian-bugs@pixar.com
Resent-From: Ian Jackson <ian@chiark.chu.cam.ac.uk>
Resent-To: debian-devel@pixar.com
Resent-Date: Thu, 19 Oct 1995 18:48:01 GMT
Resent-Message-ID: <debian-bugs-handler.660.B10191841210@pixar.com>
Resent-Sender: iwj10@cus.cam.ac.uk
X-Debian-PR-Package: gdb
X-Debian-PR-Keywords: 
Received: via spool for debian-bugs; Thu, 19 Oct 1995 18:48:01 GMT
Received: with rfc822 via encapsulated-mail; Thu, 19 Oct 1995 18:41:21 GMT
Received: from pixar.com by mongo.pixar.com with smtp
	(Smail3.1.28.1 #15) id m0t5zsj-000B7cC; Thu, 19 Oct 95 11:39 PDT
Received: from artemis.chu.cam.ac.uk by pixar.com with SMTP id AA11619
  (5.67b/IDA-1.5 for debian-bugs-pipe@mongo.pixar.com); Thu, 19 Oct 1995 11:36:51 -0700
Received: from chiark.chu.cam.ac.uk by artemis.chu.cam.ac.uk with smtp
	(Smail3.1.29.1 #33) id m0t60sA-0007uBC; Thu, 19 Oct 95 19:43 GMT
Received: by chiark.chu.cam.ac.uk
	id m0t5zpf-0002YFC
	(Debian /\oo/\ Smail3.1.29.1 #29.33); Thu, 19 Oct 95 19:36 BST
Message-Id: <m0t5zpf-0002YFC@chiark.chu.cam.ac.uk>
Date: Thu, 19 Oct 95 19:36 BST
From: Ian Jackson <ian@chiark.chu.cam.ac.uk>
To: sr1@irz301.inf.tu-dresden.de (Sven Rudolph)
Cc: Debian bugs submission address <debian-bugs@pixar.com>
In-Reply-To: <199510190118.CAA08031@irz101.inf.tu-dresden.de>
References: <199510190118.CAA08031@irz101.inf.tu-dresden.de>

Sven Rudolph writes in email to me:
> > Package: gdb
> > Version: 4.12
> >
> > As you can see below, when setting a memory breakpoint on a structure
> > member GDB uses the address of the start of the structure by mistake.
> > Applying *& to the member (to take its address and then dereference
> > it) gives correct results.
>
> (typescript deleted)
>
> You used commands that don't even exist in the current version of gdb,
> so i cannot reproduce this problem. I'm not a gdb expert, so please
> try to reproduce this problem on a current gdb (or close the bug) .

These commands have equivalents in gdb 4.14-1.  However, the
equivalents don't appear to work for me at all.  See the transcript
below.

Please can we keep this bug open until (a) the memory watchpoints,
which are a useful feature, work and (b) we see that the original bug
is fixed.

Ian.

-chiark:~/junk> cat t.c
struct foo { int a,b; };

void fong(struct foo *p, int x) { p->b=x; }

int main(int argc, char **argv) {
  struct foo f;
  f.a= 2;
  f.b= 3;
  fong(&f,4);
  f.b=5;
  fong(&f,6);
}
-chiark:~/junk> gcc -g t.c
-chiark:~/junk> gdb a.out
GDB is free software and you are welcome to 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.
GDB 4.14 (i486-debian-linux), Copyright 1995 Free Software Foundation, Inc...
(gdb) break main
Breakpoint 1 at 0x1093: file t.c, line 7.
(gdb) run
Starting program: /u/ian/junk/a.out

Breakpoint 1, main (argc=1, argv=0xbffff858) at t.c:7
7         f.a= 2;
(gdb) step
8         f.b= 3;
(gdb) step
9         fong(&f,4);
(gdb) print f
$1 = {a = 2, b = 3}
(gdb) watch f.b
Hardware watchpoint 2: f.b
(gdb) watch f.a
Hardware watchpoint 3: f.a
(gdb) watch *&f.b
Hardware watchpoint 4: *&f.b
(gdb) info watchpoints
Num Type           Disp Enb Address    What
1   breakpoint     keep y   0x00001093 in main at t.c:7
        breakpoint already hit 1 time
2   hw watchpoint  keep y   f.b
3   hw watchpoint  keep y   f.a
4   hw watchpoint  keep y   *&f.b
(gdb) cont
Continuing.
warning: Hardware watchpoint 3: Could not insert watchpoint

warning: Hardware watchpoint 4: Could not insert watchpoint

ptrace: Unknown error -1.
Cannot insert breakpoints.
The same program may be running in another process.
(gdb) quit
The program is running.  Quit anyway (and kill it)? (y or n) y
-chiark:~/junk>

Message sent:


From: iwj10@thor.cam.ac.uk (Ian Jackson)
To: Ian Jackson <ian@chiark.chu.cam.ac.uk>
Subject: Bug#660: Info received (was Bug#660: GDB gets address of structure member wrong in memory breakpoint)
In-Reply-To: <m0t5zpf-0002YFC@chiark.chu.cam.ac.uk>
References: <m0t5zpf-0002YFC@chiark.chu.cam.ac.uk>

Thank you for the additional information you have supplied regarding
this problem report.  It has been forwarded to the developers to
accompany the original report.

If you wish to continue to submit further information on your problem,
please do the same thing again: send it to debian-bugs@pixar.com, ensuring
that the Subject line starts with "Bug#660" or "Re: Bug#660" so that
we can identify it as relating to the same problem.

Please do not reply to the address at the top of this message,
unless you wish to report a problem with the bug-tracking system.

Ian Jackson
(maintainer, debian-bugs)
Ian Jackson / iwj10@thor.cam.ac.uk, with the debian-bugs tracking mechanism
This page last modified 07:43:01 GMT Wed 01 Nov