Correctly handle forward DIE references in scanner
Commit Message
The cooked index scanner has special code to handle forward DIE
references. However, a bug report lead to the discovery that this
code does not work -- the "deferred_entry::spec_offset" field is
written to but never used, i.e., the lookup is done using the wrong
key.
This patch fixes the bug and adds a regression test.
The test in the bug itself used a thread_local variable, which
provoked a failure at runtime. This test instead uses "maint print
objfiles" and then inspects to ensure that the entry in question has a
parent. This lets us avoid a clang dependency in the test.
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30271
---
gdb/dwarf2/read.c | 5 +-
gdb/testsuite/gdb.dwarf2/forward-spec.exp | 102 ++++++++++++++++++++++
2 files changed, 104 insertions(+), 3 deletions(-)
create mode 100644 gdb/testsuite/gdb.dwarf2/forward-spec.exp
Comments
>>>>> "Tom" == Tom Tromey <tom@tromey.com> writes:
Tom> The cooked index scanner has special code to handle forward DIE
Tom> references. However, a bug report lead to the discovery that this
Tom> code does not work -- the "deferred_entry::spec_offset" field is
Tom> written to but never used, i.e., the lookup is done using the wrong
Tom> key.
Tom> This patch fixes the bug and adds a regression test.
Tom> The test in the bug itself used a thread_local variable, which
Tom> provoked a failure at runtime. This test instead uses "maint print
Tom> objfiles" and then inspects to ensure that the entry in question has a
Tom> parent. This lets us avoid a clang dependency in the test.
Tom> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30271
I'm going check this in on master and gdb-13 now.
Tom
>>>>> "Tom" == Tom Tromey <tom@tromey.com> writes:
Tom> I'm going check this in on master and gdb-13 now.
I noticed in the backport that the test doesn't really verify the
result, because 13 doesn't show the symbols in "maint print objfiles".
However, I don't think this is extremely important on this branch, so
I'm going ahead.
Tom
@@ -16592,9 +16592,8 @@ cooked_indexer::make_index (cutu_reader *reader)
for (const auto &entry : m_deferred_entries)
{
- CORE_ADDR key = form_addr (entry.die_offset, m_per_cu->is_dwz);
- void *obj = m_die_range_map.find (key);
- cooked_index_entry *parent = static_cast <cooked_index_entry *> (obj);
+ void *obj = m_die_range_map.find (entry.spec_offset);
+ cooked_index_entry *parent = static_cast<cooked_index_entry *> (obj);
m_index_storage->add (entry.die_offset, entry.tag, entry.flags,
entry.name, parent, m_per_cu);
}
new file mode 100644
@@ -0,0 +1,102 @@
+# Copyright 2023 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 DWARF reader works with a a DW_AT_specification that
+# refers to a later DIE.
+
+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 -debug.S
+
+# Set up the DWARF for the test.
+set asm_file [standard_output_file $srcfile2]
+Dwarf::assemble $asm_file {
+ global srcfile
+
+ cu {} {
+ DW_TAG_compile_unit {
+ {DW_AT_language @DW_LANG_C_plus_plus}
+ {DW_AT_name $srcfile}
+ {DW_AT_comp_dir /tmp}
+
+ } {
+ declare_labels spec myint
+
+ # The new indexer has special code to compute the full
+ # name of an object that uses a specification that appears
+ # later in the DWARF.
+ DW_TAG_variable {
+ {DW_AT_specification :$spec}
+ {DW_AT_location {
+ DW_OP_const1u 23
+ DW_OP_stack_value
+ } SPECIAL_expr}
+ }
+
+ myint: DW_TAG_base_type {
+ {DW_AT_byte_size 4 DW_FORM_sdata}
+ {DW_AT_encoding @DW_ATE_signed}
+ {DW_AT_name myint}
+ }
+
+ DW_TAG_namespace {
+ {DW_AT_name ns}
+ } {
+ spec: DW_TAG_variable {
+ {DW_AT_name v}
+ {DW_AT_type :$myint}
+ {DW_AT_declaration 1 DW_FORM_flag_present}
+ }
+ }
+ }
+ }
+}
+
+if {[prepare_for_testing "failed to prepare" ${testfile} \
+ [list $srcfile $asm_file] {nodebug}]} {
+ return -1
+}
+
+set in_v 0
+gdb_test_multiple "maint print objfiles" "v has a parent" {
+ -re "^ *\\\[\[0-9\]\\\] *..cooked_index_entry\[^\r\n\]*" {
+ set in_v 0
+ exp_continue
+ }
+ -re "^ *name: *v\[\r\n\]*" {
+ set in_v 1
+ exp_continue
+ }
+ -re "^ *parent: *..cooked_index_entry .. (0|$hex)." {
+ if {$in_v} {
+ if {$expect_out(1,string) == "0"} {
+ fail $gdb_test_name
+ } else {
+ pass $gdb_test_name
+ }
+ set in_v 0
+ }
+ exp_continue
+ }
+ -re "^\[^\r\n\]*\[\r\n\]+" {
+ exp_continue
+ }
+ -re "$gdb_prompt " {
+ # Done.
+ }
+}