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[patch] Fix pr 15691, gdb crash from "Stay in DWO optimization"
- From: Doug Evans <dje at google dot com>
- To: gdb-patches at sourceware dot org
- Date: Thu, 27 Jun 2013 11:52:13 -0700
- Subject: [patch] Fix pr 15691, gdb crash from "Stay in DWO optimization"
Hi.
gdb can crash when debugging a mix of fission and non-fission compiled files.
http://sourceware.org/bugzilla/show_bug.cgi?id=15691
Regression tested on amd64-linux.
I will commit this in a few days if there are no objections.
PR symtab/15691
* dwarf2read.c (struct dwarf2_per_cu_data): New member tu_read.
(fill_in_sig_entry_from_dwo_entry): Reorganize asserts.
Add assert of sig_entry->dwo_unit == NULL.
(lookup_dwo_signatured_type): Don't assign TU to a DWO if the TU
had already been read.
(read_signatured_type): Set per_cu.tu_read.
testsuite/
* gdb.dwarf2/fission-mix.exp: New file.
* gdb.dwarf2/fission-mix.h: New file.
* gdb.dwarf2/fission-mix.c: New file.
* gdb.dwarf2/fission-mix2.c: New file.
Index: dwarf2read.c
===================================================================
RCS file: /cvs/src/src/gdb/dwarf2read.c,v
retrieving revision 1.809
diff -u -p -r1.809 dwarf2read.c
--- dwarf2read.c 20 Jun 2013 22:16:28 -0000 1.809
+++ dwarf2read.c 27 Jun 2013 18:48:13 -0000
@@ -558,6 +558,16 @@ struct dwarf2_per_cu_data
attributes in the stub. */
unsigned int reading_dwo_directly : 1;
+ /* Non-zero if the TU has been read.
+ This is used to assist the "Stay in DWO Optimization" for Fission:
+ When reading a DWO, it's faster to read TUs from the DWO instead of
+ fetching them from random other DWOs (due to comdat folding).
+ If the TU has already been read, the optimization is unnecessary
+ (and unwise - we don't want to change where gdb thinks the TU lives
+ "midflight").
+ This flag is only valid if is_debug_types is true. */
+ unsigned int tu_read : 1;
+
/* The section this CU/TU lives in.
If the DIE refers to a DWO file, this is always the original die,
not the DWO file. */
@@ -4438,11 +4448,7 @@ fill_in_sig_entry_from_dwo_entry (struct
struct signatured_type *sig_entry,
struct dwo_unit *dwo_entry)
{
- sig_entry->per_cu.section = dwo_entry->section;
- sig_entry->per_cu.offset = dwo_entry->offset;
- sig_entry->per_cu.length = dwo_entry->length;
- sig_entry->per_cu.reading_dwo_directly = 1;
- sig_entry->per_cu.objfile = objfile;
+ /* Make sure we're not clobbering something we don't expect to. */
gdb_assert (! sig_entry->per_cu.queued);
gdb_assert (sig_entry->per_cu.cu == NULL);
gdb_assert (sig_entry->per_cu.v.quick != NULL);
@@ -4450,19 +4456,26 @@ fill_in_sig_entry_from_dwo_entry (struct
gdb_assert (sig_entry->signature == dwo_entry->signature);
gdb_assert (sig_entry->type_offset_in_section.sect_off == 0);
gdb_assert (sig_entry->type_unit_group == NULL);
+ gdb_assert (sig_entry->dwo_unit == NULL);
+
+ sig_entry->per_cu.section = dwo_entry->section;
+ sig_entry->per_cu.offset = dwo_entry->offset;
+ sig_entry->per_cu.length = dwo_entry->length;
+ sig_entry->per_cu.reading_dwo_directly = 1;
+ sig_entry->per_cu.objfile = objfile;
sig_entry->type_offset_in_tu = dwo_entry->type_offset_in_tu;
sig_entry->dwo_unit = dwo_entry;
}
/* Subroutine of lookup_signatured_type.
- Create the signatured_type data structure for a TU to be read in
- directly from a DWO file, bypassing the stub.
- We do this for the case where there is no DWP file and we're using
- .gdb_index: When reading a CU we want to stay in the DWO file containing
- that CU. Otherwise we could end up reading several other DWO files (due
- to comdat folding) to process the transitive closure of all the mentioned
- TUs, and that can be slow. The current DWO file will have every type
- signature that it needs.
+ If we haven't read the TU yet, create the signatured_type data structure
+ for a TU to be read in directly from a DWO file, bypassing the stub.
+ This is the "Stay in DWO Optimization": When there is no DWP file and we're
+ using .gdb_index, then when reading a CU we want to stay in the DWO file
+ containing that CU. Otherwise we could end up reading several other DWO
+ files (due to comdat folding) to process the transitive closure of all the
+ mentioned TUs, and that can be slow. The current DWO file will have every
+ type signature that it needs.
We only do this for .gdb_index because in the psymtab case we already have
to read all the DWOs to build the type unit groups. */
@@ -4491,8 +4504,13 @@ lookup_dwo_signatured_type (struct dwarf
sig_entry = htab_find (dwarf2_per_objfile->signatured_types, &find_sig_entry);
if (sig_entry == NULL)
return NULL;
+
+ /* We can get here with the TU already read, *or* in the process of being
+ read. Don't reassign it if that's the case. Also note that if the TU is
+ already being read, it may not have come from a DWO, the program may be
+ a mix of Fission-compiled code and non-Fission-compiled code. */
/* Have we already tried to read this TU? */
- if (sig_entry->dwo_unit != NULL)
+ if (sig_entry->per_cu.tu_read)
return sig_entry;
/* Ok, this is the first time we're reading this TU. */
@@ -18598,6 +18616,7 @@ read_signatured_type (struct signatured_
init_cutu_and_read_dies (per_cu, NULL, 0, 1,
read_signatured_type_reader, NULL);
+ sig_type->per_cu.tu_read = 1;
}
/* Decode simple location descriptions.
Index: testsuite/gdb.dwarf2/fission-mix.c
===================================================================
RCS file: testsuite/gdb.dwarf2/fission-mix.c
diff -N testsuite/gdb.dwarf2/fission-mix.c
--- /dev/null 1 Jan 1970 00:00:00 -0000
+++ testsuite/gdb.dwarf2/fission-mix.c 27 Jun 2013 18:48:13 -0000
@@ -0,0 +1,33 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+ Copyright 2013 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/>. */
+
+#include "fission-mix.h"
+
+struct s foo;
+
+int
+func (int arg)
+{
+ return arg + 1;
+}
+
+int
+main ()
+{
+ foo.x = 1;
+ return func (-1);
+}
Index: testsuite/gdb.dwarf2/fission-mix.exp
===================================================================
RCS file: testsuite/gdb.dwarf2/fission-mix.exp
diff -N testsuite/gdb.dwarf2/fission-mix.exp
--- /dev/null 1 Jan 1970 00:00:00 -0000
+++ testsuite/gdb.dwarf2/fission-mix.exp 27 Jun 2013 18:48:13 -0000
@@ -0,0 +1,46 @@
+# Copyright 2013 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/>.
+
+load_lib dwarf.exp
+
+# This test can only be run on targets which support DWARF-2.
+if ![dwarf2_support] {
+ return 0
+}
+
+standard_testfile fission-mix.c fission-mix2.c
+set objfile [standard_output_file ${testfile}.o]
+set objfile2 [standard_output_file ${testfile}2.o]
+
+# Compile fission-mix.c without Fission and fission-mix2.c with Fission.
+if { [gdb_compile ${srcdir}/${subdir}/${srcfile} $objfile object {debug}] != "" } {
+ return -1
+}
+if { [gdb_compile ${srcdir}/${subdir}/${srcfile2} $objfile2 object {debug additional_flags=-gsplit-dwarf}] != "" } {
+ return -1
+}
+if {[gdb_compile "$objfile $objfile2" $binfile executable {debug}] != "" } {
+ return -1
+}
+
+clean_restart $binfile
+
+gdb_test "break main" "Breakpoint .*"
+
+# Bug 15691: gdb would crash here on an assert violation.
+# The debug info for the TU for "struct s" has already been read,
+# but gdb doesn't think so.
+# To repro the bug, --target_board=dwarf4-gdb-index, or equivalent, is needed.
+gdb_test "break func2" "Breakpoint .*"
Index: testsuite/gdb.dwarf2/fission-mix.h
===================================================================
RCS file: testsuite/gdb.dwarf2/fission-mix.h
diff -N testsuite/gdb.dwarf2/fission-mix.h
--- /dev/null 1 Jan 1970 00:00:00 -0000
+++ testsuite/gdb.dwarf2/fission-mix.h 27 Jun 2013 18:48:13 -0000
@@ -0,0 +1,23 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+ Copyright 2013 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/>. */
+
+/* A type to be recorded as a DW_TAG_type_unit. */
+
+struct s
+{
+ int x;
+};
Index: testsuite/gdb.dwarf2/fission-mix2.c
===================================================================
RCS file: testsuite/gdb.dwarf2/fission-mix2.c
diff -N testsuite/gdb.dwarf2/fission-mix2.c
--- /dev/null 1 Jan 1970 00:00:00 -0000
+++ testsuite/gdb.dwarf2/fission-mix2.c 27 Jun 2013 18:48:13 -0000
@@ -0,0 +1,27 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+ Copyright 2013 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/>. */
+
+#include "fission-mix.h"
+
+struct s bar;
+
+int
+func2 ()
+{
+ bar.x = 1;
+ return 42;
+}