C++ binary compatibility

[Mark Davies <mark%mcs.vuw.ac.nz@localhost>]

I'm copying this to tech-toolchain as the issue was discussed there a 
few weeks back and someone there might have an idea from your 
debugging.

cheers
mark

On Tue, 01 Apr 2008, Sverre Froyen wrote:
> On Friday 28 March 2008, Sverre Froyen wrote:
> > On Thursday 27 March 2008, Mark Davies wrote:
>
> ...
>
> > > Moving forward we need to either identify what the actual ABI
> > > change was and reverse it or bump the version number of the
> > > library.
> >
> > OK. I have a new libstdc++ built with -g and all my old binaries.
> >  What can I do to help track this down?
> >
> > Here's a backtrace example from artsd segfaulting:
> >
> > Program received signal SIGSEGV, Segmentation fault.
> > 0xbb606906 in std::ostream::flush (this=0xbb676620)
> >     at
> > /usr/src/gnu/dist/gcc4/libstdc++-v3/include/bits/basic_ios.h:308
> > 308           { return _M_streambuf; }
> > Current language:  auto; currently c++
> >
> > #0  0xbb606906 in std::ostream::flush (this=0xbb676620)
> >     at
> > /usr/src/gnu/dist/gcc4/libstdc++-v3/include/bits/basic_ios.h:308
> > #1  0xbb623b56 in sentry (this=0xbfbfdbeb, __in=@0xbfbfdc58,
> > __noskip=false) at
> > /usr/src/gnu/dist/gcc4/libstdc++-v3/include/bits/istream.tcc:58
> > #2 0xbb642da5 in std::operator>><char, std::char_traits<char>,
> > std::allocator<char> > (__in=@0xbfbfdc58, __str=@0xbfbfdee0) at
> > /usr/src/gnu/dist/gcc4/libstdc++-v3/src/istream.cc:277 #3 
> > 0xbb91fe60 in Arts::MCOPConfig::readListEntry ()
> >    from /usr/pkg/lib/libmcop.so.1
> > #4  0xbb917649 in readPath () from /usr/pkg/lib/libmcop.so.1
> > #5  0xbb9177c5 in Arts::MCOPUtils::traderPath ()
> > from /usr/pkg/lib/libmcop.so.1
> > #6  0xbb922676 in Arts::TraderHelper::load () from
> > /usr/pkg/lib/libmcop.so.1 #7  0xbb922730 in
> > Arts::TraderHelper::TraderHelper ()
> >    from /usr/pkg/lib/libmcop.so.1
> > #8  0xbb922778 in Arts::TraderHelper::the () from
> > /usr/pkg/lib/libmcop.so.1 #9  0xbb9239c8 in
> > Arts::TraderQuery_impl::query ()
> >    from /usr/pkg/lib/libmcop.so.1
> > #10 0x08062d9b in
> > Arts::SimpleSoundServer_impl::SimpleSoundServer_impl () #11
> > 0x0805b416 in Arts::SoundServerV2_impl::SoundServerV2_impl () #12
> > 0x0805d7b3 in SoundServerV2_impl_Factory::createInstance () #13
> > 0xbb90f87d in Arts::ObjectManager::create ()
> > from /usr/pkg/lib/libmcop.so.1
> > #14 0xbbbb8ebc in Arts::SoundServerV2_base::_create ()
>
> The segentaion fault happens because  __in._M_tie is bogus (see
> frame 1, above).  Here's a dump of __in:
>
> (gdb) print __in
> $1 = (class std::basic_istream<char,std::char_traits<char> >
>      &) @0xbfbfdc58: {<std::basic_ios<char,std::char_traits<char>
> >> = {<std::ios_base> = {_vptr.ios_base = 0xbb673360, static
> boolalpha = std::_S_boolalpha,
>       static dec = std::_S_dec, static fixed = std::_S_fixed,
>       static hex = std::_S_hex, static internal = std::_S_internal,
>       static left = std::_S_left, static oct = std::_S_oct,
>       static right = std::_S_right, static scientific =
> std::_S_scientific, static showbase = std::_S_showbase,
>       static showpoint = std::_S_showpoint, static showpos =
> std::_S_showpos, static skipws = std::_S_skipws, static unitbuf =
> std::_S_unitbuf, static uppercase = std::_S_uppercase,
>       static adjustfield = std::_S_adjustfield,
>       static basefield = std::_S_basefield,
>       static floatfield = std::_S_floatfield, static badbit =
> std::_S_badbit, static eofbit = std::_S_eofbit, static failbit =
> std::_S_failbit, static goodbit = std::_S_goodbit, static app =
> std::_S_app, static ate = std::_S_ate, static binary = std::_S_bin,
> static in = std::_S_in, static out = std::_S_out,
>       static trunc = std::_S_trunc, static beg = std::_S_beg,
>       static cur = std::_S_cur, static end = std::_S_end,
>       _M_precision = 134694080, _M_width = 6, _M_flags = 0,
>       _M_exception = 4098, _M_streambuf_state = std::_S_goodbit,
>       _M_callbacks = 0x0, _M_word_zero = {_M_pword = 0x0, _M_iword
> = 0}, _M_local_word = {{_M_pword = 0x0, _M_iword = 0}, {_M_pword =
> 0x0, _M_iword = 0}, {_M_pword = 0x0, _M_iword = 0}, {_M_pword =
> 0x0, _M_iword = 0}, {_M_pword = 0x0, _M_iword = 0}, {_M_pword =
> 0x0, _M_iword = 0}, {_M_pword = 0x0, _M_iword = 0}, {_M_pword =
> 0x0, _M_iword = 0}}, _M_word_size = 0, _M_word = 0x8, _M_ios_locale
> = { static none = 0, static ctype = 1, static numeric = 2, static
> collate = 4, static time = 8, static monetary = 16, static messages
> = 32, static all = 63, _M_impl = 0xbfbfde74, static _S_classic =
> 0xbb676620, static _S_global = 0xbb676620, static _S_categories =
> 0xbb671064, static _S_once = {pto_mutex = { ptm_magic = 858980355,
> ptm_errorcheck = 0, ptm_recursed = 0, ptm_waiters = 0x0, ptm_owner
> = 0x0}, pto_done = 1}}}, _M_tie = 0xbb676620, _M_fill = 0 '\0',
> _M_fill_init = false, _M_streambuf = 0xbfbf0000, _M_ctype =
> 0xbfbfdc60, _M_num_put = 0xbb676760, _M_num_get = 0xbb6769a0},
> _vptr.basic_istream = 0x80744ac, _M_gcount = 0}
>
> Notice that the address 0xbb676620 is pointed to by _M_tie as well
> as several other members.  In fact, 0xbb676620 contains the global
> variable __gnu_internal::c_locale_impl.
>
> (gdb) print __in._M_tie
> $2 = (class std::basic_ostream<char,std::char_traits<char> > *)
> 0xbb676620 (gdb) x 0xbb676620
> 0xbb676620 <_ZN14__gnu_internal13c_locale_implE>:       0x00000012
>
> (std::ostream::flush attempts to use the 0x12 as an address causing
> the violation)
>
> I attemped to add a breakpoint at (all) the std::basic_istream
> constructors in libstdc++, but either I missed one or it is never
> called!?
>
> Does this ring a bell with any one?  Suggestions?
>
> Thanks,
> Sverre
>
> PS I see some weirdness with gdb.  stepi in most cases work like
> continue and some times gdb places itself in the background (an fg
> seems to restore it properly).