On Wed, 2011-03-16 at 14:40 -0700, Roland McGrath wrote: > > I didn't do that, because I wanted the normal circularity check to catch > > that. If we get a failure because of any circular reference, > > self-reference or not, it is probably is something we need to > > investigate. I cannot imagine when anything like that isn't some bug in > > the producer. > > Well, that's what dwarflint is for. There is nothing algorithmically > difficult about handling direct self-reference in the hash function. > It exists in some data, whether by producer bug or not, so we have to > handle it. The kludge is just too ugly.
We cannot have ugly code :) I added a dwarflint pass for it. Attached and on the mjw/check_self_referential_die Output of warning (on dwarfcmp, the problematic binary): warning: .debug_info: DIE 0xed86a: attribute containing_type references DIE itself. warning: .debug_info: DIE 0x1710eb: attribute containing_type references DIE itself. Petr, if you think that is correct, I like to merge it to the dwarf branch. I removed the special DW_AT_containing_type case and just ignore all self referential attribute values. Although I was tempted to just remove it completely (since it is wrong, wrong, wrong). It seems Dodji just posted a patch for gcc that might fix this issue by properly outputting pointer-to-member-function. I haven't tried it yet though. http://gcc.gnu.org/ml/gcc-patches/2011-03/msg00949.html > > It this case it was > > http://git.fedorahosted.org/git/?p=elfutils.git;a=commit;h=17a29217e9145989ca15479132f8d6d8f80f0258 > > Ok, I see the method now. What is calling that? It is used to get at the die_info_pair of a debug_info_entry in for example get_die_info () from value::value_reference to access the reference_hash of the die that it points to. Cheers, Mark commit fab4929d16ea08b0929795d2cbd44f42cc161a0e Author: Mark Wielaard <[email protected]> Date: Thu Mar 17 12:46:06 2011 +0100 Workaround all self referential ref values, not just DW_AT_containing_type. diff --git a/libdw/c++/dwarf_output b/libdw/c++/dwarf_output index aeb192c..aab1598 100644 --- a/libdw/c++/dwarf_output +++ b/libdw/c++/dwarf_output @@ -1402,10 +1402,11 @@ namespace elfutils = dynamic_cast<const entry *> (it->second._m_value); if (ref != NULL) { - // Workaround weird case (bug?) - // https://fedorahosted.org/pipermail/elfutils-devel/2011-Februa - if (it->first == DW_AT_containing_type - && ref->_m_pending == this) + // Workaround weird cases of self-referential DIE. + // This really is a bug in the producer and dwarflint + // should warn about it. But it is easy to work around + // so just do it for now, by ignoring such values. + if (ref->_m_pending == this) continue; else attr_rhashes ^= ref->get_reference_hash (stack);
commit 2a511cf5310f15e18caeb345ff2a2f8d0f5ca878 Author: Mark Wielaard <[email protected]> Date: Thu Mar 17 12:38:45 2011 +0100 Add check_self_referential_die pass to dwarflint. diff --git a/dwarflint/Makefile.am b/dwarflint/Makefile.am index 7c0a9b2..821bc3b 100644 --- a/dwarflint/Makefile.am +++ b/dwarflint/Makefile.am @@ -82,6 +82,7 @@ dwarflint_SOURCES = \ check_matching_ranges.cc \ check_nodebug.cc \ check_range_out_of_scope.cc \ + check_self_referential_die.cc \ locstats.cc \ lowlevel_checks.cc lowlevel_checks.hh \ \ diff --git a/dwarflint/check_self_referential_die.cc b/dwarflint/check_self_referential_die.cc new file mode 100644 index 0000000..1f1dfe8 --- /dev/null +++ b/dwarflint/check_self_referential_die.cc @@ -0,0 +1,86 @@ +/* Pedantic checking of DWARF files. + Copyright (C) 2011 Red Hat, Inc. + This file is part of Red Hat elfutils. + + Red Hat elfutils is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by the + Free Software Foundation; version 2 of the License. + + Red Hat elfutils is distributed in the hope that it will be useful, but + WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + General Public License for more details. + + You should have received a copy of the GNU General Public License along + with Red Hat elfutils; if not, write to the Free Software Foundation, + Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301 USA. + + Red Hat elfutils is an included package of the Open Invention Network. + An included package of the Open Invention Network is a package for which + Open Invention Network licensees cross-license their patents. No patent + license is granted, either expressly or impliedly, by designation as an + included package. Should you wish to participate in the Open Invention + Network licensing program, please visit www.openinventionnetwork.com + <http://www.openinventionnetwork.com>. */ + +#ifdef HAVE_CONFIG_H +# include <config.h> +#endif + +#include "highlevel_check.hh" +#include "../src/dwarfstrings.h" +#include "all-dies-it.hh" +#include "pri.hh" +#include "messages.hh" +#include <map> + +using elfutils::dwarf; + +namespace +{ + class check_self_referential_die + : public highlevel_check<check_self_referential_die> + { + public: + static checkdescriptor const *descriptor () + { + static checkdescriptor cd + (checkdescriptor::create ("check_self_referential_die") + .inherit<highlevel_check<check_self_referential_die> > () + .description ( +"A reference attribute referencing the DIE itself is suspicious.\n" +"One example is a DW_AT_containing_type pointing to itself.\n" +" https://fedorahosted.org/pipermail/elfutils-devel/2011-February/001794.html\n"; + )); + return &cd; + } + + explicit check_self_referential_die (checkstack &stack, dwarflint &lint) + : highlevel_check<check_self_referential_die> (stack, lint) + { + for (all_dies_iterator<dwarf> it = all_dies_iterator<dwarf> (dw); + it != all_dies_iterator<dwarf> (); ++it) + { + dwarf::debug_info_entry const &die = *it; + for (dwarf::debug_info_entry::attributes_type::const_iterator + at = die.attributes ().begin (); + at != die.attributes ().end (); ++at) + { + dwarf::attr_value const &val = (*at).second; + if (val.what_space () == dwarf::VS_reference) + { + dwarf::debug_info_entry ref = *val.reference (); + if (ref.identity () == die.identity ()) + wr_message (to_where (die), cat (mc_impact_3, + mc_acc_suboptimal, + mc_die_rel)) + << "attribute " << dwarf::attributes::name ((*at).first) + << " references DIE itself." << std::endl; + } + } + } + } + }; + + reg<check_self_referential_die> reg; +}
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