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[gdb/symtab] Handle PU without import in "save gdb-index"

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Consider the test-case added in this patch, with resulting dwarf:
...
  Compilation Unit @ offset 0xc7:
   Length:        0x2c (32-bit)
   Version:       4
   Abbrev Offset: 0x64
   Pointer Size:  8
 <0><d2>: Abbrev Number: 2 (DW_TAG_partial_unit)
    <d3>   DW_AT_language    : 2        (non-ANSI C)
    <d4>   DW_AT_name        : imported_unit.c
 <1><e4>: Abbrev Number: 3 (DW_TAG_base_type)
    <e5>   DW_AT_byte_size   : 4
    <e6>   DW_AT_encoding    : 5        (signed)
    <e7>   DW_AT_name        : int
 <1><eb>: Abbrev Number: 4 (DW_TAG_subprogram)
    <ec>   DW_AT_name        : main
    <f1>   DW_AT_type        : <0xe4>
    <f5>   DW_AT_external    : 1
 <1><f6>: Abbrev Number: 0
  Compilation Unit @ offset 0xf7:
   Length:        0x2c (32-bit)
   Version:       4
   Abbrev Offset: 0x85
   Pointer Size:  8
 <0><102>: Abbrev Number: 2 (DW_TAG_compile_unit)
    <103>   DW_AT_language    : 2       (non-ANSI C)
    <104>   DW_AT_name        : <artificial>
 <1><111>: Abbrev Number: 3 (DW_TAG_subprogram)
    <112>   DW_AT_abstract_origin: <0xeb>
    <116>   DW_AT_low_pc      : 0x4004a7
    <11e>   DW_AT_high_pc     : 0x4004b2
 <1><126>: Abbrev Number: 0
...

When run with target board cc-with-gdb-index, we run into:
...
(gdb) break main
warning: (Internal error: pc 0x4004a7 in read in CU, but not in symtab.)
<repeat>
warning: (Internal error: pc 0x4004ab in read in CU, but not in symtab.)
<repeat>
Breakpoint 1 at 0x4004ab
(gdb) PASS: gdb.dwarf2/imported-unit-runto-main.exp: setting breakpoint at main
run
Starting program: /data/gdb_versions/devel/build/gdb/testsuite/outputs/gdb.dwarf2/imported-unit-runto-main/imported-unit-runto-main
warning: (Internal error: pc 0x4004a7 in read in CU, but not in symtab.)
<repeat>
warning: (Internal error: pc 0x4004ab in read in CU, but not in symtab.)
<repeat>

Breakpoint 1, warning: (Internal error: pc 0x4004ab in read in CU, but not in symtab.)
warning: (Internal error: pc 0x4004ab in read in CU, but not in symtab.)
<repeat>
0x00000000004004ab in main ()
warning: (Internal error: pc 0x4004ab in read in CU, but not in symtab.)
<repeat>
(gdb) FAIL: gdb.dwarf2/imported-unit-runto-main.exp: running to main in runto
...

Looking at the .gdb_index section contents using objdump --dwarf=gdb_index, we
have:
...
CU table:
[  0] 0x0 - 0x2d
[  1] 0x2e - 0xa4
[  2] 0xa5 - 0xc6
[  3] 0xf7 - 0x126
[  4] 0x127 - 0x2de
[  5] 0x2df - 0x300

Address table:
00000000004004a7 00000000004004b2 4

Symbol table:
[489] main: 4 [global, function]
...
We see that both the main symbol, and main address range map to CU 4, which has
offset range 0x127 - 0x2de, while main actually is contained in CU 3 at offset
range 0xf7 - 0x126.

This is caused by this continue in write_gdbindex, which triggers for the PU:
...
      /* CU of a shared file from 'dwz -m' may be unused by this main file.
        It may be referenced from a local scope but in such case it does not
        need to be present in .gdb_index.  */
      if (psymtab == NULL)
       continue;
...
The continue causes the PU to be skipped in the CU table (we can see that the
PU offset range 0xc7-0xf6 is missing) but the references are not taking that
into account.

I've tried fixing this in the optimal way, by updating the references, but ran
into trouble when follow_die_offset tries to find the CU for the inter-CU
ref.  Because the PU is missing from the CU table,
dwarf2_find_containing_comp_unit bisects to the wrong CU.

Fix this by not skipping the PU in the CU table.

Build and reg-tested on x86_64-linux, with native and target boards
cc-with-gdb-index, cc-with-dwz and cc-with-dwz-m.

gdb/ChangeLog:

2020-04-16  Tom de Vries  <tdevries@suse.de>

	PR symtab/25791
	* dwarf2/index-write.c (write_gdbindex): Generate CU table entries for
	CUs without psymtab.

gdb/testsuite/ChangeLog:

2020-04-16  Tom de Vries  <tdevries@suse.de>

	PR symtab/25791
	* gdb.dwarf2/gdb-add-index.exp (add_gdb_index): Move ...
	(ensure_gdb_index): and factor out and move ...
	* lib/gdb.exp (add_gdb_index, ensure_gdb_index): ... here.
	* gdb.dwarf2/imported-unit-runto-main.exp: New file.
This commit is contained in:
Tom de Vries 2020-04-16 14:56:32 +02:00
parent 97ed802d15
commit efba5c2319
6 changed files with 160 additions and 48 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
gdb/ChangeLog
View File

@ -1,3 +1,9 @@
2020-04-16 Tom de Vries <tdevries@suse.de>
PR symtab/25791
* dwarf2/index-write.c (write_gdbindex): Generate CU table entries for
CUs without psymtab.
2020-04-16 Kevin Buettner <kevinb@redhat.com>
* python/python.c (do_start_initialization): Don't call

19
gdb/dwarf2/index-write.c
View File

@ -1426,18 +1426,15 @@ write_gdbindex (struct dwarf2_per_objfile *dwarf2_per_objfile, FILE *out_file,
= dwarf2_per_objfile->all_comp_units[i];
partial_symtab *psymtab = per_cu->v.psymtab;
/* CU of a shared file from 'dwz -m' may be unused by this main file.
It may be referenced from a local scope but in such case it does not
need to be present in .gdb_index. */
if (psymtab == NULL)
continue;
if (psymtab != NULL)
{
if (psymtab->user == NULL)
recursively_write_psymbols (objfile, psymtab, &symtab,
psyms_seen, i);
if (psymtab->user == NULL)
recursively_write_psymbols (objfile, psymtab, &symtab,
psyms_seen, i);
const auto insertpair = cu_index_htab.emplace (psymtab, i);
gdb_assert (insertpair.second);
const auto insertpair = cu_index_htab.emplace (psymtab, i);
gdb_assert (insertpair.second);
}
/* The all_comp_units list contains CUs read from the objfile as well as
from the eventual dwz file. We need to place the entry in the

8
gdb/testsuite/ChangeLog
View File

@ -1,3 +1,11 @@
2020-04-16 Tom de Vries <tdevries@suse.de>
PR symtab/25791
* gdb.dwarf2/gdb-add-index.exp (add_gdb_index): Move ...
(ensure_gdb_index): and factor out and move ...
* lib/gdb.exp (add_gdb_index, ensure_gdb_index): ... here.
* gdb.dwarf2/imported-unit-runto-main.exp: New file.
2020-04-16 Tom de Vries <tdevries@suse.de>
* gdb.base/maint-expand-symbols-header-file.exp: Set language before

40
gdb/testsuite/gdb.dwarf2/gdb-add-index.exp
View File

@ -27,48 +27,14 @@ if { [prepare_for_testing "failed to prepare" "${testfile}" \
return -1
}
# Add a .gdb_index section to PROGRAM.
# PROGRAM is assumed to be the output of standard_output_file.
# Returns the 0 if there is a failure, otherwise 1.
proc add_gdb_index { program } {
global srcdir GDB env BUILD_DATA_DIRECTORY
set contrib_dir "$srcdir/../contrib"
set env(GDB) "$GDB --data-directory=$BUILD_DATA_DIRECTORY"
set result [catch "exec $contrib_dir/gdb-add-index.sh $program" output]
if { $result != 0 } {
verbose -log "result is $result"
verbose -log "output is $output"
return 0
}
return 1
}
# Build a copy of the program with an index (.gdb_index/.debug_names).
# But only if the toolchain didn't already create one: gdb doesn't support
# building an index from a program already using one.
set test "check if index present"
gdb_test_multiple "mt print objfiles ${testfile}" $test {
-re "gdb_index.*${gdb_prompt} $" {
set binfile_with_index $binfile
}
-re "debug_names.*${gdb_prompt} $" {
set binfile_with_index $binfile
}
-re "Psymtabs.*${gdb_prompt} $" {
if { [add_gdb_index $binfile] != "1" } {
return -1
}
set binfile_with_index $binfile
}
if { [ensure_gdb_index $binfile] == -1 } {
return -1
}
# Ok, we have a copy of $binfile with an index.
# Restart gdb and verify the index was used.
clean_restart ${binfile_with_index}
clean_restart ${binfile}
gdb_test "mt print objfiles ${testfile}" \
"(gdb_index|debug_names).*" \
"index used"

92
gdb/testsuite/gdb.dwarf2/imported-unit-runto-main.exp Normal file
View File

@ -0,0 +1,92 @@
# Copyright 2020 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 and use gas.
if {![dwarf2_support]} {
return 0
};
standard_testfile main.c .S
set executable ${testfile}
set asm_file [standard_output_file ${srcfile2}]
# We need to know the size of integer types in order to write some of the
# debugging info we'd like to generate.
if [prepare_for_testing "failed to prepare" ${testfile} ${srcfile}] {
return -1
}
# Create the DWARF.
Dwarf::assemble $asm_file {
declare_labels cu_label main_label int_label
declare_labels aaa_label
set int_size [get_sizeof "int" 4]
global srcdir subdir srcfile
extern main
set main_range [function_range main ${srcdir}/${subdir}/${srcfile}]
set main_start [lindex $main_range 0]
set main_length [lindex $main_range 1]
cu {} {
cu_label: partial_unit {
{language @DW_LANG_C}
{name "imported_unit.c"}
} {
int_label: base_type {
{byte_size $int_size sdata}
{encoding @DW_ATE_signed}
{name int}
}
main_label: subprogram {
{name main}
{type :$int_label}
{external 1 flag}
}
}
}
cu {} {
compile_unit {
{language @DW_LANG_C}
{name "<artificial>"}
} {
subprogram {
{abstract_origin %$main_label}
{low_pc $main_start addr}
{high_pc "$main_start + $main_length" addr}
}
}
}
}
if { [prepare_for_testing "failed to prepare" ${testfile} \
[list $srcfile $asm_file] {nodebug}] } {
return -1
}
if { [ensure_gdb_index $binfile] == -1 } {
return -1
}
clean_restart ${binfile}
runto main message

43
gdb/testsuite/lib/gdb.exp
View File

@ -7038,5 +7038,48 @@ proc verify_psymtab_expanded { filename readin } {
}
}
# Add a .gdb_index section to PROGRAM.
# PROGRAM is assumed to be the output of standard_output_file.
# Returns the 0 if there is a failure, otherwise 1.
proc add_gdb_index { program } {
global srcdir GDB env BUILD_DATA_DIRECTORY
set contrib_dir "$srcdir/../contrib"
set env(GDB) "$GDB --data-directory=$BUILD_DATA_DIRECTORY"
set result [catch "exec $contrib_dir/gdb-add-index.sh $program" output]
if { $result != 0 } {
verbose -log "result is $result"
verbose -log "output is $output"
return 0
}
return 1
}
# Add a .gdb_index section to PROGRAM, unless it alread has an index
# (.gdb_index/.debug_names). Gdb doesn't support building an index from a
# program already using one. Return 1 if a .gdb_index was added, return 0
# if it already contained an index, and -1 if an error occurred.
proc ensure_gdb_index { binfile } {
set testfile [file tail $binfile]
set test "check if index present"
gdb_test_multiple "mt print objfiles ${testfile}" $test {
-re -wrap "gdb_index.*" {
return 0
}
-re -wrap "debug_names.*" {
return 0
}
-re -wrap "Psymtabs.*" {
if { [add_gdb_index $binfile] != "1" } {
return -1
}
return 1
}
}
return -1
}
# Always load compatibility stuff.
load_lib future.exp