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Re: RFC c++ debugging thread (fwd)
Hi again...
here's a typical gdb session; I am trying to find a bug (obviously)
and getting VERY frustrated at the moment.
Problem at hand:
~/c++/libcw/src/libcwd/MegaHALv9r1/objs>./MegaHAL++ IRCPlugin.so -n botcrashx -c bottestchan -s diemen.nl.eu.undernet.org
__ __ _ _ _ _ ___
| \/ | ___ __ _ __ _| | | | / \ | | __ __/ _ \
| |\/| |/ _ \/ _` |/ _` | |_| | / _ \ | | \ \ / / (_) |
| | | | __/ (_| | (_| | _ |/ ___ \| |___ \ V / \__, |
|_| |_|\___|\__, |\__,_|_| |_/_/ \_\_____| \_/ /_/r1
|___/
Copyright(C) 1998 Jason Jutchens
Copyright(C) 2000 Orlando Bassotto
-Logo Designed by Daniele Nicolucci-
------------------------------------------------------------
BFD : Calling libcw::debug::dlopen "(nil)".
MALLOC : malloc(13) = <unfinished>
BFD : Warning: Address 0x400073b1 in section .text does not have a line number, perhaps the unit containing the function
`_dl_dst_substitute' wasn't compiled with flag -g
MALLOC : <continued> 0x813f440
MALLOC : calloc(416, 1) = <unfinished>
BFD : Warning: Address 0x4000bcfc in section .text does not have a line number, perhaps the unit containing the function
`_dl_lookup_versioned_symbol_skip' wasn't compiled with flag -g
MALLOC : <continued> 0x8248de0
MALLOC : malloc(25) = <unfinished>
BFD : Warning: Address 0x4000bd0d in section .text does not have a line number, perhaps the unit containing the function
`_dl_lookup_versioned_symbol_skip' wasn't compiled with flag -g
MALLOC : <continued> 0x81ff670
MALLOC : malloc(141) = <unfinished>
BFD : Warning: Address 0x4000be49 in section .text does not have a line number, perhaps the unit containing the function
`_dl_lookup_versioned_symbol_skip' wasn't compiled with flag -g
MALLOC : <continued> 0x81fed80
MALLOC : malloc(212) = <unfinished>
BFD : address 0x4000cfcc corresponds to dl-deps.c:495
MALLOC : <continued> 0x8248f90
MALLOC : calloc(6, 16) = <unfinished>
BFD : address 0x4000ef89 corresponds to dl-version.c:286
MALLOC : <continued> 0x804f280
MALLOC : malloc(84) = <unfinished>
BFD : Warning: Address 0x40366d57 in section .text does not have a line number, perhaps the unit containing the function
`getutmpx' wasn't compiled with flag -g
MALLOC : <continued> 0x8200648
Segmentation fault (core dumped)
Now I start the gdb session:
~/c++/libcw/src/libcwd/MegaHALv9r1/objs>gdb ./MegaHAL++ core
GNU gdb 5.0rh-5 Red Hat Linux 7.1
Copyright 2001 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"...
Core was generated by `./MegaHAL++ IRCPlugin.so -n botcrashx -c bottestchan -s diemen.nl.eu.undernet.o'.
Program terminated with signal 11, Segmentation fault.
Error while mapping shared library sections:
libMegaHAL++.so: Success.
Error while mapping shared library sections:
IRCPlugin.so: Success.
Reading symbols from /usr/lib/libreadline.so.4.1...done.
Loaded symbols for /usr/lib/libreadline.so.4.1
Reading symbols from /usr/lib/libncurses.so.5...done.
Loaded symbols for /usr/lib/libncurses.so.5
Reading symbols from libMegaHAL++.so...done.
Loaded symbols for libMegaHAL++.so
Reading symbols from /lib/libdl.so.2...done.
Loaded symbols for /lib/libdl.so.2
Reading symbols from /home/carlo/c++/libcw/src/libcwd/.libs/libcwd.so.0...done.
Loaded symbols for /home/carlo/c++/libcw/src/libcwd/.libs/libcwd.so.0
Reading symbols from /usr/lib/libbfd-2.10.91.0.2.so...done.
Loaded symbols for /usr/lib/libbfd-2.10.91.0.2.so
Reading symbols from /usr/local/gcc-3.0/lib/libstdc++.so.3...done.
Loaded symbols for /usr/local/gcc-3.0/lib/libstdc++.so.3
Reading symbols from /lib/libm.so.6...done.
Loaded symbols for /lib/libm.so.6
Reading symbols from /usr/local/gcc-3.0/lib/libgcc_s.so.1...done.
Loaded symbols for /usr/local/gcc-3.0/lib/libgcc_s.so.1
Reading symbols from /lib/libc.so.6...done.
Loaded symbols for /lib/libc.so.6
Reading symbols from /lib/ld-linux.so.2...done.
Loaded symbols for /lib/ld-linux.so.2
Reading symbols from IRCPlugin.so...done.
Loaded symbols for IRCPlugin.so
#0 0x400ed869 in std::ostream::sentry::sentry(std::ostream&) (this=0xbffff290, __os=@0x10)
at /usr/local/gcc-3.0/include/g++-v3/bits/ostream.tcc:39
39 : _M_ok(__os.good()), _M_os(__os)
The reason for the core dump is no doubt that __os==@0x10.
Question: Why?
(gdb) up
#1 0x400eefe2 in std::ostream::flush() (this=0x10) at /usr/local/gcc-3.0/include/g++-v3/bits/ostream.tcc:385
385 sentry __cerb(*this);
(gdb) up
#2 0x400ed8c5 in std::ostream::sentry::sentry(std::ostream&) (this=0xbffff2f8, __os=@0x820a9e0)
at /usr/local/gcc-3.0/include/g++-v3/bits/ostream.tcc:43
43 __os.tie()->flush();
Apparently tie() returns 0x10. Question: Why?
(gdb) p __os
$1 = (basic_ostream<char,std::char_traits<char> > &) @0x820a9e0: {<basic_ios<char,std::char_traits<char> >> = <invalid address>,
_vptr. = 0x81ffa58}
Well, that didn't help. Lets try stepping to this point.
(gdb) b 43
Breakpoint 1 at 0x400ed8a6: file /usr/local/gcc-3.0/include/g++-v3/bits/ostream.tcc, line 43.
(gdb) r IRCPlugin.so -n botcrashx -c bottestchan -s diemen.nl.eu.undernet.o
Starting program: /home/carlo/c++/libcw/src/libcwd/MegaHALv9r1/objs/./MegaHAL++ IRCPlugin.so -n botcrashx -c bottestchan -s diemen.nl.eu.undernet.o
Error while mapping shared library sections:
libMegaHAL++.so: Success.
Error in re-setting breakpoint 1:
No source file named /usr/local/gcc-3.0/include/g++-v3/bits/ostream.tcc.
Error in re-setting breakpoint 1:
No source file named /usr/local/gcc-3.0/include/g++-v3/bits/ostream.tcc.
Error in re-setting breakpoint 1:
No source file named /usr/local/gcc-3.0/include/g++-v3/bits/ostream.tcc.
Error in re-setting breakpoint 1:
No source file named /usr/local/gcc-3.0/include/g++-v3/bits/ostream.tcc.
__ __ _ _ _ _ ___
| \/ | ___ __ _ __ _| | | | / \ | | __ __/ _ \
| |\/| |/ _ \/ _` |/ _` | |_| | / _ \ | | \ \ / / (_) |
| | | | __/ (_| | (_| | _ |/ ___ \| |___ \ V / \__, |
|_| |_|\___|\__, |\__,_|_| |_/_/ \_\_____| \_/ /_/r1
|___/
Copyright(C) 1998 Jason Jutchens
Copyright(C) 2000 Orlando Bassotto
-Logo Designed by Daniele Nicolucci-
------------------------------------------------------------
BFD : Calling libcw::debug::dlopen "(nil)".
MALLOC : malloc(13) = <unfinished>
BFD : Warning: Address 0x400073b1 in section .text does not have a line number, perhaps the unit containing the function
`_dl_dst_substitute' wasn't compiled with flag -g
MALLOC : <continued> 0x81e6dc8
MALLOC : calloc(416, 1) = <unfinished>
BFD : Warning: Address 0x4000bcfc in section .text does not have a line number, perhaps the unit containing the function
`_dl_lookup_versioned_symbol_skip' wasn't compiled with flag -g
MALLOC : <continued> 0x8253e00
MALLOC : malloc(25) = <unfinished>
BFD : Warning: Address 0x4000bd0d in section .text does not have a line number, perhaps the unit containing the function
`_dl_lookup_versioned_symbol_skip' wasn't compiled with flag -g
MALLOC : <continued> 0x81fcee8
MALLOC : malloc(141) = <unfinished>
BFD : Warning: Address 0x4000be49 in section .text does not have a line number, perhaps the unit containing the function
`_dl_lookup_versioned_symbol_skip' wasn't compiled with flag -g
MALLOC : <continued> 0x81fc5f8
MALLOC : malloc(212) = <unfinished>
BFD : address 0x4000cfcc corresponds to dl-deps.c:495
MALLOC : <continued> 0x8253fb0
MALLOC : calloc(6, 16) = <unfinished>
BFD : address 0x4000ef89 corresponds to dl-version.c:286
MALLOC : <continued> 0x804f280
Error while mapping shared library sections:
IRCPlugin.so: Success.
MALLOC : malloc(84) = <unfinished>
BFD : Warning: Address 0x40366d57 in section .text does not have a line number, perhaps the unit containing the function
`getutmpx' wasn't compiled with flag -g
MALLOC : <continued> 0x80508d0
Program received signal SIGSEGV, Segmentation fault.
0x400ed869 in std::ostream::sentry::sentry(std::ostream&) (this=0xbffff270, __os=@0x10)
at /usr/local/gcc-3.0/include/g++-v3/bits/ostream.tcc:39
39 : _M_ok(__os.good()), _M_os(__os)
Ok, what happened with my breakpoint?
Perhaps I need to do it in steps?
(gdb) d 1
(gdb) b main
Breakpoint 2 at 0x8049c33: file src/MegaHAL++.cpp, line 129.
(gdb) r IRCPlugin.so -n botcrashx -c bottestchan -s diemen.nl.eu.undernet.o
The program being debugged has been started already.
Start it from the beginning? (y or n) y
Starting program: /home/carlo/c++/libcw/src/libcwd/MegaHALv9r1/objs/./MegaHAL++ IRCPlugin.so -n botcrashx -c bottestchan -s diemen.nl.eu.undernet.o
Error while mapping shared library sections:
libMegaHAL++.so: Success.
Error in re-setting breakpoint 1:
No source file named /usr/local/gcc-3.0/include/g++-v3/bits/ostream.tcc.
Error in re-setting breakpoint 1:
No source file named /usr/local/gcc-3.0/include/g++-v3/bits/ostream.tcc.
Error in re-setting breakpoint 1:
No source file named /usr/local/gcc-3.0/include/g++-v3/bits/ostream.tcc.
Error in re-setting breakpoint 1:
No source file named /usr/local/gcc-3.0/include/g++-v3/bits/ostream.tcc.
Breakpoint 2, main (argc=8, argv=0xbffff5bc) at src/MegaHAL++.cpp:129
129 Debug( dc::notice.on() ); // Turn on the NOTICE Debug Channel
(gdb) b ostream.tcc:43
Breakpoint 3 at 0x400ed8a6: file /usr/local/gcc-3.0/include/g++-v3/bits/ostream.tcc, line 43.
(gdb) c
Continuing.
__ __ _ _ _ _ ___
| \/ | ___ __ _ __ _| | | | / \ | | __ __/ _ \
| |\/| |/ _ \/ _` |/ _` | |_| | / _ \ | | \ \ / / (_) |
| | | | __/ (_| | (_| | _ |/ ___ \| |___ \ V / \__, |
|_| |_|\___|\__, |\__,_|_| |_/_/ \_\_____| \_/ /_/r1
|___/
Copyright(C) 1998 Jason Jutchens
Copyright(C) 2000 Orlando Bassotto
-Logo Designed by Daniele Nicolucci-
------------------------------------------------------------
BFD : Calling libcw::debug::dlopen "(nil)".
MALLOC : malloc(13) = <unfinished>
BFD : Warning: Address 0x400073b1 in section .text does not have a line number, perhaps the unit containing the function
`_dl_dst_substitute' wasn't compiled with flag -g
MALLOC : <continued> 0x81e6dc8
MALLOC : calloc(416, 1) = <unfinished>
BFD : Warning: Address 0x4000bcfc in section .text does not have a line number, perhaps the unit containing the function
`_dl_lookup_versioned_symbol_skip' wasn't compiled with flag -g
MALLOC : <continued> 0x8253e00
MALLOC : malloc(25) = <unfinished>
BFD : Warning: Address 0x4000bd0d in section .text does not have a line number, perhaps the unit containing the function
`_dl_lookup_versioned_symbol_skip' wasn't compiled with flag -g
MALLOC : <continued> 0x81fcee8
MALLOC : malloc(141) = <unfinished>
BFD : Warning: Address 0x4000be49 in section .text does not have a line number, perhaps the unit containing the function
`_dl_lookup_versioned_symbol_skip' wasn't compiled with flag -g
MALLOC : <continued> 0x81fc5f8
MALLOC : malloc(212) = <unfinished>
BFD : address 0x4000cfcc corresponds to dl-deps.c:495
MALLOC : <continued> 0x8253fb0
MALLOC : calloc(6, 16) = <unfinished>
BFD : address 0x4000ef89 corresponds to dl-version.c:286
MALLOC : <continued> 0x804f280
Error while mapping shared library sections:
IRCPlugin.so: Success.
MALLOC : malloc(84) = <unfinished>
BFD : Warning: Address 0x40366d57 in section .text does not have a line number, perhaps the unit containing the function
`getutmpx' wasn't compiled with flag -g
MALLOC : <continued> 0x80508d0
Breakpoint 3, std::ostream::sentry::sentry(std::ostream&) (this=0xbffff2d8, __os=@0x8207fd8)
at /usr/local/gcc-3.0/include/g++-v3/bits/ostream.tcc:43
43 __os.tie()->flush();
Ok, that worked.
(gdb) p __os
$2 = (basic_ostream<char,std::char_traits<char> > &) @0x8207fd8: {<basic_ios<char,std::char_traits<char> >> = <invalid address>,
_vptr. = 0x81fd2d0}
Still no luck. Not wanting to take any risk, lets use 'si':
(gdb) si
0x400ed8a9 43 __os.tie()->flush();
(gdb)
0x400ed8ac 43 __os.tie()->flush();
(gdb)
0x400ed8ae 43 __os.tie()->flush();
(gdb)
0x400ed8b1 43 __os.tie()->flush();
(gdb)
0x400ed8b3 43 __os.tie()->flush();
(gdb)
0x400ed8b6 43 __os.tie()->flush();
(gdb)
0x400ed8b7 43 __os.tie()->flush();
(gdb)
0x400d16a8 in _init () from /home/carlo/c++/libcw/src/libcwd/.libs/libcwd.so.0
(gdb)
std::basic_ios<char, std::char_traits<char> >::tie() const (this=0xbffff2d8) at /usr/local/gcc-3.0/include/g++-v3/bits/basic_ios.h:145
145 { return _M_tie; }
(gdb) p _M_tie
$3 = (basic_ostream<char,std::char_traits<char> > *) 0x10
(gdb) p *this
$4 = {<ios_base> = {static boolalpha = Cannot access memory at address 0x0
Still no luck getting any overview of this object.
Perhaps when I start a bit higher in the stack frame?
(gdb) bt
#0 std::basic_ios<char, std::char_traits<char> >::tie() const (this=0xbffff2d8) at /usr/local/gcc-3.0/include/g++-v3/bits/basic_ios.h:145
#1 0x400f62f8 in std::basic_ostream<char, std::char_traits<char> >& std::operator<< <std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char) (__out=@0x8207fd8, __c=40 '(') at /usr/local/gcc-3.0/include/g++-v3/bits/ostream.tcc:577
#2 0x400d81f0 in libcw::debug::cwbfd::object_file_ct::object_file_ct(char const*, void*) (this=0x81fd2d0,
filename=0xbffff78a "IRCPlugin.so", base=0xffffffff) at bfd.cc:403
#3 0x400dade9 in libcw::debug::dlopen(char const*, int) (name=0xbffff78a "IRCPlugin.so", flags=258) at bfd.cc:1133
#4 0x08049d1c in main (argc=8, argv=0xbffff5bc) at src/MegaHAL++.cpp:151
#5 0x40276f31 in __libc_start_main (main=0x8049c20 <main>, argc=8, ubp_av=0xbffff5bc, init=0x8049528 <_init>, fini=0x804a890 <_fini>,
rtld_fini=0x4000e274 <_dl_fini>, stack_end=0xbffff5b4) at ../sysdeps/generic/libc-start.c:129
(gdb) up
#1 0x400f62f8 in std::basic_ostream<char, std::char_traits<char> >& std::operator<< <std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char) (__out=@0x8207fd8, __c=40 '(') at /usr/local/gcc-3.0/include/g++-v3/bits/ostream.tcc:577
577 typename __ostream_type::sentry __cerb(__out);
(gdb) p __out
$5 = (basic_ostream<char,std::char_traits<char> > &) @0x8207fd8: {<basic_ios<char,std::char_traits<char> >> = <invalid address>,
_vptr. = 0x81fd2d0}
As expected.
(gdb) up
#2 0x400d81f0 in libcw::debug::cwbfd::object_file_ct::object_file_ct(char const*, void*) (this=0x81fd2d0,
filename=0xbffff78a "IRCPlugin.so", base=0xffffffff) at bfd.cc:403
403 Dout(dc::continued, '(' << hex << lbase << ") ");
Now that sucks, Dout() is a macro that does:
#define DEBUGCHANNELS ::libcw::debug::channels
#define Dout(cntrl, data) LibcwDout(DEBUGCHANNELS, ::libcw::debug::libcw_do, cntrl, data)
#define LibcwDout( dc_namespace, debug_obj, cntrl, data ) \
do \
{ \
DEBUGDEBUGLIBCWDOUTMARKER \
if (debug_obj._off < 0) \
{ \
using namespace ::libcw::debug; \
bool on; \
{ \
using namespace dc_namespace; \
on = (debug_obj|cntrl).on; \
} \
if (on) \
{ \
debug_obj.start(); \
(*debug_obj.current_oss) << data; \
debug_obj.finish(); \
} \
} \
} while(0)
And apparently we are here inside "(*debug_obj.current_oss) << data;".
Lets have a look at the global object 'debug_obj':
(gdb) p '::libcw::debug::libcw_do'
No symbol "::libcw::debug::libcw_do" in current context.
Right
(gdb) p 'libcw::debug::libcw_do'
$6 = {_off = -1, current = 0x8207fd0, current_oss = 0x8207fd8, {channel_set = {<channel_set_data_st> = {label = 0x0, mask = 8192, on = true,
debug_object = 0x40138640}, <No data fields>}, continued_channel_set = {<channel_set_data_st> = {label = 0x0, mask = 8192,
on = true, debug_object = 0x40138640}, <No data fields>}}, orig_os = 0x4022e0c0, os = 0x4022e0c0, start_expected = true,
unfinished_expected = false, laf_stack = {st = {0x8207fd0, 0x0 <repeats 63 times>}, p = 0x40138664, end = 0x40138764}, off_count = 0,
continued_stack = {st = {0 <repeats 64 times>}, p = 0x40138770, end = 0x40138870}, margin = {len = 0, str = 0x4010d588 "",
orig_str = 0x4010d588 "", str_is_allocated = false}, marker = {len = 2, str = 0x4010d486 ": ", orig_str = 0x4010d486 ": ",
str_is_allocated = false}, indent = 0, saved_os = 0x0, interactive = true, initialized = true}
Slightly better. Now there is 'current_oss': 0x8207fd8.
So this must be the problem: current_oss->tie() returns 0x10.
(gdb) p 'libcw::debug::libcw_do'.current_oss
$7 = (basic_ostream<char,std::char_traits<char> > *) 0x8207fd8
(gdb) p *'libcw::debug::libcw_do'.current_oss
virtual baseclass botch
I think I'll have to catch this at the moment it is assigned...
(gdb) r
The program being debugged has been started already.
Start it from the beginning? (y or n) y
Starting program: /home/carlo/c++/libcw/src/libcwd/MegaHALv9r1/objs/./MegaHAL++ IRCPlugin.so -n botcrashx -c bottestchan -s diemen.nl.eu.undernet.o
Error while mapping shared library sections:
libMegaHAL++.so: Success.
Error in re-setting breakpoint 3:
No source file named ostream.tcc.
Error in re-setting breakpoint 3:
No source file named ostream.tcc.
Error in re-setting breakpoint 3:
No source file named ostream.tcc.
Error in re-setting breakpoint 3:
No source file named ostream.tcc.
Breakpoint 2, main (argc=8, argv=0xbffff5bc) at src/MegaHAL++.cpp:129
129 Debug( dc::notice.on() ); // Turn on the NOTICE Debug Channel
(gdb) d 3
(gdb) watch 'libcw::debug::libcw_do'.current_oss
Hardware watchpoint 4: libcw::debug::libcw_do.current_oss
(gdb) c
Continuing.
__ __ _ _ _ _ ___
| \/ | ___ __ _ __ _| | | | / \ | | __ __/ _ \
| |\/| |/ _ \/ _` |/ _` | |_| | / _ \ | | \ \ / / (_) |
| | | | __/ (_| | (_| | _ |/ ___ \| |___ \ V / \__, |
|_| |_|\___|\__, |\__,_|_| |_/_/ \_\_____| \_/ /_/r1
|___/
Copyright(C) 1998 Jason Jutchens
Copyright(C) 2000 Orlando Bassotto
-Logo Designed by Daniele Nicolucci-
------------------------------------------------------------
Hardware watchpoint 4: libcw::debug::libcw_do.current_oss
Old value = ( *) 0x40138968
New value = ( *) 0x8207fd8
libcw::debug::debug_ct::start() (this=0x40138640) at debug.cc:277
277 if (!(channel_set.mask & (noprefix_cf|nolabel_cf|blank_margin_cf|blank_label_cf|blank_marker_cf)))
(gdb) p 'libcw::debug::libcw_do'.current_oss->_M_tie
Segmentation fault (core dumped)
Great, now gdb core dumped...
Ok, sorry for the long mail :/
I guess this is all related to the same bug/problem. Is it known?
Anything I can do/upgrade to fix it? I am using i686-pc-gnu-linux,
g++-3.0, binutils-2.10.91.0.2...
--
Carlo Wood <carlo@alinoe.com>