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From: Tom de Vries <vries@sourceware.org> To: gdb-cvs@sourceware.org Subject: [binutils-gdb] [gdb/symtab] Fix bad compile unit index complaint Date: Thu, 21 Jul 2022 11:05:42 +0000 (GMT) [thread overview] Message-ID: <20220721110542.BE8B33858D28@sourceware.org> (raw) https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=2fe9a3c41faa71b1f2bde40e818187491a5a9925 commit 2fe9a3c41faa71b1f2bde40e818187491a5a9925 Author: Tom de Vries <tdevries@suse.de> Date: Thu Jul 21 13:05:39 2022 +0200 [gdb/symtab] Fix bad compile unit index complaint I noticed this code in dw2_debug_names_iterator::next: ... case DW_IDX_compile_unit: /* Don't crash on bad data. */ if (ull >= per_bfd->all_comp_units.size ()) { complaint (_(".debug_names entry has bad CU index %s" " [in module %s]"), pulongest (ull), objfile_name (objfile)); continue; } per_cu = per_bfd->get_cu (ull); break; ... This code used to DTRT, before we started keeping both CUs and TUs in all_comp_units. Fix by using "per_bfd->all_comp_units.size () - per_bfd->tu_stats.nr_tus" instead. It's hard to produce a test-case for this, but let's try at least to trigger the complaint somehow. We start out by creating an exec with .debug_types and .debug_names: ... $ gcc -g ~/hello.c -fdebug-types-section $ gdb-add-index -dwarf-5 a.out ... and verify that we don't see any complaints: ... $ gdb -q -batch -iex "set complaints 100" ./a.out ... We look at the CU and TU table using readelf -w and conclude that we have nr_cus == 6 and nr_tus == 1. Now override ull in dw2_debug_names_iterator::next for the DW_IDX_compile_unit case to 6, and we have: ... $ gdb -q -batch -iex "set complaints 100" ./a.out During symbol reading: .debug_names entry has bad CU index 6 [in module a.out] ... After this, it still crashes because this code in dw2_debug_names_iterator::next: ... /* Skip if already read in. */ if (m_per_objfile->symtab_set_p (per_cu)) goto again; ... is called with per_cu == nullptr. Fix this by skipping the entry if per_cu == nullptr. Now revert the fix and observe that the complaint disappears, so we've confirmed that the fix is required. A somewhat similar issue for .gdb_index in dw2_symtab_iter_next has been filed as PR29367. Tested on x86_64-linux, with native and target board cc-with-debug-names. Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29336 Diff: --- gdb/dwarf2/read.c | 26 +++++++++++++++++--------- 1 file changed, 17 insertions(+), 9 deletions(-) diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c index bcd01107377..42230607fe0 100644 --- a/gdb/dwarf2/read.c +++ b/gdb/dwarf2/read.c @@ -4970,15 +4970,19 @@ dw2_debug_names_iterator::next () switch (attr.dw_idx) { case DW_IDX_compile_unit: - /* Don't crash on bad data. */ - if (ull >= per_bfd->all_comp_units.size ()) - { - complaint (_(".debug_names entry has bad CU index %s" - " [in module %s]"), - pulongest (ull), - objfile_name (objfile)); - continue; - } + { + /* Don't crash on bad data. */ + int nr_cus = (per_bfd->all_comp_units.size () + - per_bfd->tu_stats.nr_tus); + if (ull >= nr_cus) + { + complaint (_(".debug_names entry has bad CU index %s" + " [in module %s]"), + pulongest (ull), + objfile_name (objfile)); + continue; + } + } per_cu = per_bfd->get_cu (ull); break; case DW_IDX_type_unit: @@ -5016,6 +5020,10 @@ dw2_debug_names_iterator::next () } } + /* Skip if we couldn't find a valid CU/TU index. */ + if (per_cu == nullptr) + goto again; + /* Skip if already read in. */ if (m_per_objfile->symtab_set_p (per_cu)) goto again;
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