Date: Wed, 15 Mar 2000 10:24:47 +0200 From: Maxim Sobolev <sobomax@altavista.net> To: current@freebsd.org Cc: stable@freebsd.org Subject: gcc -Os optimisation broken (RELENG_4) Message-ID: <38CF48CF.59A100D7@altavista.net>
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Hi,
I've just upgraded my production server to the 4.0-RELEASE and found that
squid23 when compiled with -Os option dying with signal 11 on each attempt to
load page. When I recompiled it with -O fault disappeared. After some digging
into the sources with gdb I found that fault came from dereferencing NULL
pointer somewhere in the DNS query procedures. I've tracked the source of this
pointer and found that the function rfc1035QuestionPack (rfc1035.c) called from
rfc1035BuildAQuery receives NULL pointer instead of the supplied hostname as a
3rd argument. Following is two debugging sessions with squid compiled with -Os
and -O (faulty call is in the end of the output):
-Maxim
-Os:
Script started on Wed Mar 15 10:16:16 2000
root@vega# gdb squid
GNU gdb 4.18
[GDB copyright omitted]
(gdb) set args -C -N -d 10
(gdb) b rfc1035BuildAQuery
Breakpoint 1 at 0x8096cb1: file rfc1035.c, line 472.
(gdb) r
Starting program: /usr/ports/www/squid23/work/squid-2.3.STABLE2/src/squid -C -N
-d 10
[unrelevant squid output omitted]
Breakpoint 1, 0x8096cb1 in rfc1035BuildAQuery (
hostname=0x84a5900 "www.yahoo.com", buf=0x8212c00 "", szp=0x8212e00)
at rfc1035.c:472
472 size_t sz = *szp;
(gdb) n
473 memset(&h, '\0', sizeof(h));
(gdb)
472 size_t sz = *szp;
(gdb)
473 memset(&h, '\0', sizeof(h));
(gdb)
474 h.id = rfc1035Qid();
(gdb)
476 h.rd = 1;
(gdb)
477 h.opcode = 0; /* QUERY */
(gdb)
478 h.qdcount = (unsigned int) 1;
(gdb)
479 offset += rfc1035HeaderPack(buf + offset, sz - offset, &h);
(gdb)
480 offset += rfc1035QuestionPack(buf + offset,
(gdb) print hostname
$1 = 0x84a5900 "www.yahoo.com"
(gdb) list
475 h.qr = 0;
476 h.rd = 1;
477 h.opcode = 0; /* QUERY */
478 h.qdcount = (unsigned int) 1;
479 offset += rfc1035HeaderPack(buf + offset, sz - offset, &h);
480 offset += rfc1035QuestionPack(buf + offset,
481 sz - offset,
482 hostname,
483 RFC1035_TYPE_A,
484 RFC1035_CLASS_IN);
(gdb) s
rfc1035QuestionPack (buf=0x8212c0c "", sz=500, name=0x0, type=1, class=1)
at rfc1035.c:201
201 off += rfc1035NamePack(buf + off, sz - off, name);
(gdb) q
The program is running. Exit anyway? (y or n) y
root@vega# exit
Script done on Wed Mar 15 10:17:46 2000
-O:
Script started on Wed Mar 15 09:57:49 2000
root@vega# gdb squid
[GDB copyright omitted]
(gdb) set args -C -N -d 10
(gdb) b rfc1035BuildAQuery
Breakpoint 1 at 0x8096321: file rfc1035.c, line 469.
(gdb) r
Starting program: /usr/ports/www/squid23/work/squid-2.3.STABLE2/src/squid -C -N
-d 10
[unrelevant squid output omitted]
Breakpoint 1, 0x8096321 in rfc1035BuildAQuery (
hostname=0x84a5900 "www.yahoo.com", buf=0x8212c00 "", szp=0x8212e00)
at rfc1035.c:469
469 {
(gdb) n
472 size_t sz = *szp;
(gdb)
473 memset(&h, '\0', sizeof(h));
(gdb)
474 h.id = rfc1035Qid();
(gdb)
475 h.qr = 0;
(gdb)
476 h.rd = 1;
(gdb)
477 h.opcode = 0; /* QUERY */
(gdb)
478 h.qdcount = (unsigned int) 1;
(gdb)
479 offset += rfc1035HeaderPack(buf + offset, sz - offset, &h);
(gdb)
480 offset += rfc1035QuestionPack(buf + offset,
(gdb) print hostname
$1 = 0x84a5900 "www.yahoo.com"
(gdb) list
475 h.qr = 0;
476 h.rd = 1;
477 h.opcode = 0; /* QUERY */
478 h.qdcount = (unsigned int) 1;
479 offset += rfc1035HeaderPack(buf + offset, sz - offset, &h);
480 offset += rfc1035QuestionPack(buf + offset,
481 sz - offset,
482 hostname,
483 RFC1035_TYPE_A,
484 RFC1035_CLASS_IN);
(gdb) s
rfc1035QuestionPack (buf=0x8212c0c "", sz=500, name=0x84a5900 "www.yahoo.com",
type=1, class=1) at rfc1035.c:201
201 off += rfc1035NamePack(buf + off, sz - off, name);
(gdb) q
The program is running. Exit anyway? (y or n) y
root@vega# exit
Script done on Wed Mar 15 09:59:28 2000
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