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gdb/gdb-symtab-return-correct-reader-for-top-level-cu-in.patch

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From 84b9218d98eb2ac242fe3afc81598206279f7b13 Mon Sep 17 00:00:00 2001
From: Tom de Vries <tdevries@suse.de>
Date: Thu, 22 Aug 2024 10:00:27 +0200
Subject: [PATCH] [gdb/symtab] Return correct reader for top-level CU in
cooked_indexer::ensure_cu_exists
With the test-case included in this patch, we run into:
...
$ gdb -q -batch $exec
Dwarf Error: Could not find abbrev number 3 in CU at offset 0xdb \
[in module $exec]
...
The debug info consists of two CUs:
...
Compilation Unit @ offset 0xb2:
Length: 0x25 (32-bit)
Version: 4
Abbrev Offset: 0x6c
Pointer Size: 8
<0><bd>: Abbrev Number: 1 (DW_TAG_compile_unit)
<be> DW_AT_language : 2 (non-ANSI C)
<1><bf>: Abbrev Number: 2 (DW_TAG_subprogram)
<c0> DW_AT_low_pc : 0x4004a7
<c8> DW_AT_high_pc : 0x4004b2
<d0> DW_AT_specification: <0xe8>
<1><d4>: Abbrev Number: 3 (DW_TAG_subprogram)
<d5> DW_AT_name : main
<1><da>: Abbrev Number: 0
Compilation Unit @ offset 0xdb:
Length: 0xf (32-bit)
Version: 4
Abbrev Offset: 0x86
Pointer Size: 8
<0><e6>: Abbrev Number: 1 (DW_TAG_compile_unit)
<e7> DW_AT_language : 2 (non-ANSI C)
<1><e8>: Abbrev Number: 2 (DW_TAG_subprogram)
<e9> DW_AT_specification: <0xd4>
<1><ed>: Abbrev Number: 0
...
where:
- DIE 0xbf in CU@0xb2 contains an inter-CU reference to
- DIE 0xe8 in CU@0xdb, which contains an inter-CU reference to
- DIE 0xd4 back in CU@0xb2.
The dwarf error is caused by this bit of code in
cooked_indexer::ensure_cu_exists:
...
if (per_cu == m_per_cu)
return reader;
...
The dwarf error happens as follows:
- a cutu_reader A is created for CU@0xb2
- using cutu_reader A, the cooked index reader starts indexing dies, with
m_per_cu set to CU@0xb2
- while indexing it scans the attributes of DIE 0xbf and encounters the
inter-CU reference to DIE 0xe8
- it calls cooked_indexer::ensure_cu_exists, which creates a cutu_reader B for
CU@0xdb and returns it
- using cutu_reader B, it continues scanning attributes of DIE 0xe8 and
encounters the inter-CU reference to DIE 0xd4
- it calls cooked_indexer::ensure_cu_exists, the problematic bit is triggered
and cutu_reader B is returned
- using cutu_reader B, it continues scanning attributes of DIE 0xd4
- this goes wrong because:
- the attributes of the DIE are encoded using the abbreviation table at
offset 0x6c, while
- the decoding is done using cutu_reader B which uses the abbreviation table
at offset 0x86.
Fix this by removing the problematic if clause.
Since cutu_reader A is not preserved in m_index_storage,
cooked_indexer::ensure_cu_exists cannot find it there and creates a duplicate
cutu_reader C for CU@0xb2. Fix this in process_psymtab_comp_unit by preserving
the cutu_reader A as well in m_index_storage.
Tested on x86_64-linux and aarch64-linux.
PR symtab/32081
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=32081
Approved-By: Tom Tromey <tom@tromey.com>
Reported-By: Andreas Schwab <schwab@linux-m68k.org>
---
gdb/dwarf2/read.c | 35 ++++++-----
.../dw2-inter-cu-forth-and-back.exp | 60 +++++++++++++++++++
2 files changed, 80 insertions(+), 15 deletions(-)
create mode 100644 gdb/testsuite/gdb.dwarf2/dw2-inter-cu-forth-and-back.exp
diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index 8f2d7a34aef..b72b5fe8c83 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -4880,28 +4880,35 @@ process_psymtab_comp_unit (dwarf2_per_cu_data *this_cu,
dwarf2_per_objfile *per_objfile,
cooked_index_storage *storage)
{
- cutu_reader reader (this_cu, per_objfile, nullptr, nullptr, false,
- storage->get_abbrev_cache ());
+ cutu_reader *reader = storage->get_reader (this_cu);
+ if (reader == nullptr)
+ {
+ cutu_reader new_reader (this_cu, per_objfile, nullptr, nullptr, false,
+ storage->get_abbrev_cache ());
- if (reader.comp_unit_die == nullptr)
- return;
+ if (new_reader.comp_unit_die == nullptr || new_reader.dummy_p)
+ return;
- if (reader.dummy_p)
- {
- /* Nothing. */
+ std::unique_ptr<cutu_reader> copy
+ (new cutu_reader (std::move (new_reader)));
+ reader = storage->preserve (std::move (copy));
}
- else if (this_cu->is_debug_types)
- build_type_psymtabs_reader (&reader, storage);
- else if (reader.comp_unit_die->tag != DW_TAG_partial_unit)
+
+ if (reader->comp_unit_die == nullptr || reader->dummy_p)
+ return;
+
+ if (this_cu->is_debug_types)
+ build_type_psymtabs_reader (reader, storage);
+ else if (reader->comp_unit_die->tag != DW_TAG_partial_unit)
{
bool nope = false;
if (this_cu->scanned.compare_exchange_strong (nope, true))
{
- prepare_one_comp_unit (reader.cu, reader.comp_unit_die,
+ prepare_one_comp_unit (reader->cu, reader->comp_unit_die,
language_minimal);
gdb_assert (storage != nullptr);
- cooked_indexer indexer (storage, this_cu, reader.cu->lang ());
- indexer.make_index (&reader);
+ cooked_indexer indexer (storage, this_cu, reader->cu->lang ());
+ indexer.make_index (reader);
}
}
}
@@ -16280,8 +16287,6 @@ cooked_indexer::ensure_cu_exists (cutu_reader *reader,
if (!per_cu->scanned.compare_exchange_strong (nope, true))
return nullptr;
}
- if (per_cu == m_per_cu)
- return reader;
cutu_reader *result = m_index_storage->get_reader (per_cu);
if (result == nullptr)
diff --git a/gdb/testsuite/gdb.dwarf2/dw2-inter-cu-forth-and-back.exp b/gdb/testsuite/gdb.dwarf2/dw2-inter-cu-forth-and-back.exp
new file mode 100644
index 00000000000..62674bdb700
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/dw2-inter-cu-forth-and-back.exp
@@ -0,0 +1,60 @@
+# Copyright 2024 Free Software Foundation, Inc.
+
+# This program 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; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program 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 this program. If not, see <http://www.gnu.org/licenses/>.
+
+# Check that the cooked index reader can handle inter-CU references:
+# - DIE1@CU1 -> DIE2@CU2
+# - DIE2@CU2 -> DIE3@CU1.
+
+load_lib dwarf.exp
+
+# This test can only be run on targets which support DWARF-2 and use gas.
+require dwarf2_support
+
+standard_testfile main.c .S
+
+# Create the DWARF.
+set asm_file [standard_output_file $srcfile2]
+Dwarf::assemble $asm_file {
+ declare_labels label1 label2
+
+ cu {} {
+ compile_unit {{language @DW_LANG_C}} {
+ subprogram {
+ {MACRO_AT_range { main }}
+ {DW_AT_specification %$label1}
+ }
+
+ label2: subprogram {
+ {DW_AT_name main}
+ }
+ }
+ }
+
+ cu {} {
+ compile_unit {{language @DW_LANG_C}} {
+ label1: subprogram {
+ {DW_AT_specification %$label2}
+ }
+ }
+ }
+}
+
+if [prepare_for_testing "failed to prepare" $testfile \
+ [list $asm_file $srcfile] {nodebug}] {
+ return -1
+}
+
+# Regression test for PR32081.
+gdb_assert { ![regexp -nocase "error:" $gdb_file_cmd_msg] } "No Error message"
base-commit: 102b31b0b7f62e6e4f685e725f325f2ab6283c2a
--
2.35.3
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