* [PATCH][gdb/symtab] Remove superfluous end-of-sequence marker
@ 2021-01-04 13:59 Tom de Vries
2021-01-04 16:27 ` Bernd Edlinger
0 siblings, 1 reply; 3+ messages in thread
From: Tom de Vries @ 2021-01-04 13:59 UTC (permalink / raw)
To: gdb-patches
Hi,
While working on PR26935 I noticed that when running test-case
gdb.base/morestack.exp with target board unix/-m32/-fPIE/-pie and ld linker,
I get this linetable fragment for morestack.S using readelf -wL:
...
CU: ../../../../libgcc/config/i386/morestack.S:
Line number Starting address View Stmt
109 0xc9c x
...
838 0xe03 x
- 0xe04
636 0 x
637 0x3 x
- 0x4
...
but with "maint info line-table" I get:
...
INDEX LINE ADDRESS IS-STMT
0 END 0x00000004 Y
1 109 0x00000c9c Y
...
110 838 0x00000e03 Y
111 END 0x00000e04 Y
...
So, apparently the entries with addresses 0x0 and 0x3 are filtered out
because the addresses are out of range, but the same doesn't happen with the
end-of-seq terminator.
Fix this by filtering out end-of-seq terminators that do not actually
terminate anything.
Tested on x86_64-linux.
Any comments?
Thanks,
- Tom
[gdb/symtab] Remove superfluous end-of-sequence marker
gdb/ChangeLog:
2021-01-04 Tom de Vries <tdevries@suse.de>
* buildsym.c (buildsym_compunit::record_line): Filter out end-of-seq
terminators that do not terminate anything.
gdb/testsuite/ChangeLog:
2021-01-04 Tom de Vries <tdevries@suse.de>
* gdb.dwarf2/dw2-out-of-range-end-of-seq.exp: New file.
---
gdb/buildsym.c | 8 ++
.../gdb.dwarf2/dw2-out-of-range-end-of-seq.exp | 94 ++++++++++++++++++++++
2 files changed, 102 insertions(+)
diff --git a/gdb/buildsym.c b/gdb/buildsym.c
index 1d8c579b7b8..245aecf0c38 100644
--- a/gdb/buildsym.c
+++ b/gdb/buildsym.c
@@ -714,6 +714,14 @@ buildsym_compunit::record_line (struct subfile *subfile, int line,
break;
subfile->line_vector->nitems--;
}
+
+ /* Ignore an end-of-sequence marker marking an empty sequence. */
+ struct linetable_entry *last
+ = (subfile->line_vector->nitems == 0
+ ? nullptr
+ : &subfile->line_vector->item[subfile->line_vector->nitems - 1]);
+ if (last == nullptr || last->line == 0)
+ return;
}
e = subfile->line_vector->item + subfile->line_vector->nitems++;
diff --git a/gdb/testsuite/gdb.dwarf2/dw2-out-of-range-end-of-seq.exp b/gdb/testsuite/gdb.dwarf2/dw2-out-of-range-end-of-seq.exp
new file mode 100644
index 00000000000..7a32a01389c
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/dw2-out-of-range-end-of-seq.exp
@@ -0,0 +1,94 @@
+# Copyright 2021 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 an out-of-range DW_LNE_end_sequence is removed from the
+# line table.
+
+load_lib dwarf.exp
+
+# This test can only be run on targets which support DWARF-2 and use gas.
+if {![dwarf2_support]} {
+ verbose "Skipping $gdb_test_file_name."
+ return 0
+}
+
+# The .c files use __attribute__.
+if [get_compiler_info] {
+ return -1
+}
+if !$gcc_compiled {
+ verbose "Skipping $gdb_test_file_name."
+ return 0
+}
+
+standard_testfile main.c -dw.S
+
+set asm_file [standard_output_file $srcfile2]
+Dwarf::assemble $asm_file {
+ declare_labels Llines
+ global srcdir subdir srcfile
+
+ cu {} {
+ compile_unit {
+ {language @DW_LANG_C}
+ {name $srcfile}
+ {stmt_list $Llines DW_FORM_sec_offset}
+ } {
+ subprogram {
+ {external 1 flag}
+ {MACRO_AT_func {main}}
+ }
+ }
+ }
+
+ lines {version 2} Llines {
+ include_dir "${srcdir}/${subdir}"
+ file_name "$srcfile" 1
+
+ program {
+ {DW_LNE_set_address main_label}
+ {line 1}
+ {DW_LNS_copy}
+
+ {DW_LNS_advance_pc 1}
+ {DW_LNE_end_sequence}
+
+ {DW_LNE_set_address 0}
+ {line 2}
+ {DW_LNS_copy}
+
+ {DW_LNS_advance_pc 1}
+ {DW_LNE_end_sequence}
+ }
+ }
+}
+
+if { [prepare_for_testing "failed to prepare" ${testfile} \
+ [list $srcfile $asm_file] {nodebug}] } {
+ return -1
+}
+
+if ![runto_main] {
+ return -1
+}
+
+gdb_test_multiple "maint info line-table" "END with address 1 eliminated" {
+ -re -wrap "END *0x0*1 Y \r\n.*" {
+ fail $gdb_test_name
+ }
+ -re -wrap "" {
+ pass $gdb_test_name
+ }
+}
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH][gdb/symtab] Remove superfluous end-of-sequence marker
2021-01-04 13:59 [PATCH][gdb/symtab] Remove superfluous end-of-sequence marker Tom de Vries
@ 2021-01-04 16:27 ` Bernd Edlinger
2021-01-04 18:44 ` Tom de Vries
0 siblings, 1 reply; 3+ messages in thread
From: Bernd Edlinger @ 2021-01-04 16:27 UTC (permalink / raw)
To: Tom de Vries, gdb-patches
On 1/4/21 2:59 PM, Tom de Vries wrote:
> Hi,
>
> While working on PR26935 I noticed that when running test-case
> gdb.base/morestack.exp with target board unix/-m32/-fPIE/-pie and ld linker,
> I get this linetable fragment for morestack.S using readelf -wL:
> ...
> CU: ../../../../libgcc/config/i386/morestack.S:
> Line number Starting address View Stmt
> 109 0xc9c x
> ...
> 838 0xe03 x
> - 0xe04
>
> 636 0 x
> 637 0x3 x
> - 0x4
> ...
> but with "maint info line-table" I get:
> ...
> INDEX LINE ADDRESS IS-STMT
> 0 END 0x00000004 Y
> 1 109 0x00000c9c Y
> ...
> 110 838 0x00000e03 Y
> 111 END 0x00000e04 Y
> ...
>
> So, apparently the entries with addresses 0x0 and 0x3 are filtered out
> because the addresses are out of range, but the same doesn't happen with the
> end-of-seq terminator.
>
> Fix this by filtering out end-of-seq terminators that do not actually
> terminate anything.
>
> Tested on x86_64-linux.
>
> Any comments?
>
> Thanks,
> - Tom
>
> [gdb/symtab] Remove superfluous end-of-sequence marker
>
> gdb/ChangeLog:
>
> 2021-01-04 Tom de Vries <tdevries@suse.de>
>
> * buildsym.c (buildsym_compunit::record_line): Filter out end-of-seq
> terminators that do not terminate anything.
>
> gdb/testsuite/ChangeLog:
>
> 2021-01-04 Tom de Vries <tdevries@suse.de>
>
> * gdb.dwarf2/dw2-out-of-range-end-of-seq.exp: New file.
>
> ---
> gdb/buildsym.c | 8 ++
> .../gdb.dwarf2/dw2-out-of-range-end-of-seq.exp | 94 ++++++++++++++++++++++
> 2 files changed, 102 insertions(+)
>
> diff --git a/gdb/buildsym.c b/gdb/buildsym.c
> index 1d8c579b7b8..245aecf0c38 100644
> --- a/gdb/buildsym.c
> +++ b/gdb/buildsym.c
> @@ -714,6 +714,14 @@ buildsym_compunit::record_line (struct subfile *subfile, int line,
> break;
> subfile->line_vector->nitems--;
> }
> +
> + /* Ignore an end-of-sequence marker marking an empty sequence. */
> + struct linetable_entry *last
> + = (subfile->line_vector->nitems == 0
> + ? nullptr
> + : &subfile->line_vector->item[subfile->line_vector->nitems - 1]);
> + if (last == nullptr || last->line == 0)
> + return;
> }
>
What you want to achieve here can probably be done more easily this way:
diff --git a/gdb/buildsym.c b/gdb/buildsym.c
index 1d8c579..dda83f7 100644
--- a/gdb/buildsym.c
+++ b/gdb/buildsym.c
@@ -710,6 +710,8 @@ struct blockvector *
while (subfile->line_vector->nitems > 0)
{
e = subfile->line_vector->item + subfile->line_vector->nitems - 1;
+ if (e->line == 0)
+ return;
if (e->pc != pc)
break;
subfile->line_vector->nitems--;
I wonder however where the out-of-range line entries are filtered away.
Would it be better to filter the end of sequence markers there?
Bernd.
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH][gdb/symtab] Remove superfluous end-of-sequence marker
2021-01-04 16:27 ` Bernd Edlinger
@ 2021-01-04 18:44 ` Tom de Vries
0 siblings, 0 replies; 3+ messages in thread
From: Tom de Vries @ 2021-01-04 18:44 UTC (permalink / raw)
To: Bernd Edlinger, gdb-patches
[-- Attachment #1: Type: text/plain, Size: 3672 bytes --]
On 1/4/21 5:27 PM, Bernd Edlinger wrote:
> On 1/4/21 2:59 PM, Tom de Vries wrote:
>> Hi,
>>
>> While working on PR26935 I noticed that when running test-case
>> gdb.base/morestack.exp with target board unix/-m32/-fPIE/-pie and ld linker,
>> I get this linetable fragment for morestack.S using readelf -wL:
>> ...
>> CU: ../../../../libgcc/config/i386/morestack.S:
>> Line number Starting address View Stmt
>> 109 0xc9c x
>> ...
>> 838 0xe03 x
>> - 0xe04
>>
>> 636 0 x
>> 637 0x3 x
>> - 0x4
>> ...
>> but with "maint info line-table" I get:
>> ...
>> INDEX LINE ADDRESS IS-STMT
>> 0 END 0x00000004 Y
>> 1 109 0x00000c9c Y
>> ...
>> 110 838 0x00000e03 Y
>> 111 END 0x00000e04 Y
>> ...
>>
>> So, apparently the entries with addresses 0x0 and 0x3 are filtered out
>> because the addresses are out of range, but the same doesn't happen with the
>> end-of-seq terminator.
>>
>> Fix this by filtering out end-of-seq terminators that do not actually
>> terminate anything.
>>
>> Tested on x86_64-linux.
>>
>> Any comments?
>>
>> Thanks,
>> - Tom
>>
>> [gdb/symtab] Remove superfluous end-of-sequence marker
>>
>> gdb/ChangeLog:
>>
>> 2021-01-04 Tom de Vries <tdevries@suse.de>
>>
>> * buildsym.c (buildsym_compunit::record_line): Filter out end-of-seq
>> terminators that do not terminate anything.
>>
>> gdb/testsuite/ChangeLog:
>>
>> 2021-01-04 Tom de Vries <tdevries@suse.de>
>>
>> * gdb.dwarf2/dw2-out-of-range-end-of-seq.exp: New file.
>>
>> ---
>> gdb/buildsym.c | 8 ++
>> .../gdb.dwarf2/dw2-out-of-range-end-of-seq.exp | 94 ++++++++++++++++++++++
>> 2 files changed, 102 insertions(+)
>>
>> diff --git a/gdb/buildsym.c b/gdb/buildsym.c
>> index 1d8c579b7b8..245aecf0c38 100644
>> --- a/gdb/buildsym.c
>> +++ b/gdb/buildsym.c
>> @@ -714,6 +714,14 @@ buildsym_compunit::record_line (struct subfile *subfile, int line,
>> break;
>> subfile->line_vector->nitems--;
>> }
>> +
>> + /* Ignore an end-of-sequence marker marking an empty sequence. */
>> + struct linetable_entry *last
>> + = (subfile->line_vector->nitems == 0
>> + ? nullptr
>> + : &subfile->line_vector->item[subfile->line_vector->nitems - 1]);
>> + if (last == nullptr || last->line == 0)
>> + return;
>> }
>>
>
> What you want to achieve here can probably be done more easily this way:
>
> diff --git a/gdb/buildsym.c b/gdb/buildsym.c
> index 1d8c579..dda83f7 100644
> --- a/gdb/buildsym.c
> +++ b/gdb/buildsym.c
> @@ -710,6 +710,8 @@ struct blockvector *
> while (subfile->line_vector->nitems > 0)
> {
> e = subfile->line_vector->item + subfile->line_vector->nitems - 1;
> + if (e->line == 0)
> + return;
> if (e->pc != pc)
> break;
> subfile->line_vector->nitems--;
>
>
Hi Bernd,
Thanks for the review.
Indeed, that's less verbose than the current patch, but to me it feels
more convoluted. I'd rather keep the additional test out of the loop.
I did realize because of your comment that in both cases we're dealing
with the last entry in the table, so I've rewritten the patch to use a
last variable in the loop, and to reuse it afterwards.
> I wonder however where the out-of-range line entries are filtered away.
> Would it be better to filter the end of sequence markers there?
I'm also curious about that, but I don't think it matters much.
Committed to trunk as attached.
Thanks,
- Tom
[-- Attachment #2: 0001-gdb-symtab-Remove-superfluous-end-of-sequence-marker.patch --]
[-- Type: text/x-patch, Size: 5142 bytes --]
[gdb/symtab] Remove superfluous end-of-sequence marker
While working on PR26935 I noticed that when running test-case
gdb.base/morestack.exp with target board unix/-m32/-fPIE/-pie and ld linker,
I get this linetable fragment for morestack.S using readelf -wL:
...
CU: ../../../../libgcc/config/i386/morestack.S:
Line number Starting address View Stmt
109 0xc9c x
...
838 0xe03 x
- 0xe04
636 0 x
637 0x3 x
- 0x4
...
but with "maint info line-table" I get:
...
INDEX LINE ADDRESS IS-STMT
0 END 0x00000004 Y
1 109 0x00000c9c Y
...
110 838 0x00000e03 Y
111 END 0x00000e04 Y
...
So, apparently the entries with addresses 0x0 and 0x3 are filtered out
because the addresses are out of range, but the same doesn't happen with the
end-of-seq terminator.
Fix this by filtering out end-of-seq terminators that do not actually
terminate anything.
Tested on x86_64-linux.
gdb/ChangeLog:
2021-01-04 Tom de Vries <tdevries@suse.de>
* buildsym.c (buildsym_compunit::record_line): Filter out end-of-seq
terminators that do not terminate anything.
gdb/testsuite/ChangeLog:
2021-01-04 Tom de Vries <tdevries@suse.de>
* gdb.dwarf2/dw2-out-of-range-end-of-seq.exp: New file.
---
gdb/buildsym.c | 9 ++-
.../gdb.dwarf2/dw2-out-of-range-end-of-seq.exp | 94 ++++++++++++++++++++++
2 files changed, 101 insertions(+), 2 deletions(-)
diff --git a/gdb/buildsym.c b/gdb/buildsym.c
index 1d8c579b7b8..0f7449fed97 100644
--- a/gdb/buildsym.c
+++ b/gdb/buildsym.c
@@ -707,13 +707,18 @@ buildsym_compunit::record_line (struct subfile *subfile, int line,
anyway. */
if (line == 0)
{
+ struct linetable_entry *last = nullptr;
while (subfile->line_vector->nitems > 0)
{
- e = subfile->line_vector->item + subfile->line_vector->nitems - 1;
- if (e->pc != pc)
+ last = subfile->line_vector->item + subfile->line_vector->nitems - 1;
+ if (last->pc != pc)
break;
subfile->line_vector->nitems--;
}
+
+ /* Ignore an end-of-sequence marker marking an empty sequence. */
+ if (last == nullptr || last->line == 0)
+ return;
}
e = subfile->line_vector->item + subfile->line_vector->nitems++;
diff --git a/gdb/testsuite/gdb.dwarf2/dw2-out-of-range-end-of-seq.exp b/gdb/testsuite/gdb.dwarf2/dw2-out-of-range-end-of-seq.exp
new file mode 100644
index 00000000000..7a32a01389c
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/dw2-out-of-range-end-of-seq.exp
@@ -0,0 +1,94 @@
+# Copyright 2021 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 an out-of-range DW_LNE_end_sequence is removed from the
+# line table.
+
+load_lib dwarf.exp
+
+# This test can only be run on targets which support DWARF-2 and use gas.
+if {![dwarf2_support]} {
+ verbose "Skipping $gdb_test_file_name."
+ return 0
+}
+
+# The .c files use __attribute__.
+if [get_compiler_info] {
+ return -1
+}
+if !$gcc_compiled {
+ verbose "Skipping $gdb_test_file_name."
+ return 0
+}
+
+standard_testfile main.c -dw.S
+
+set asm_file [standard_output_file $srcfile2]
+Dwarf::assemble $asm_file {
+ declare_labels Llines
+ global srcdir subdir srcfile
+
+ cu {} {
+ compile_unit {
+ {language @DW_LANG_C}
+ {name $srcfile}
+ {stmt_list $Llines DW_FORM_sec_offset}
+ } {
+ subprogram {
+ {external 1 flag}
+ {MACRO_AT_func {main}}
+ }
+ }
+ }
+
+ lines {version 2} Llines {
+ include_dir "${srcdir}/${subdir}"
+ file_name "$srcfile" 1
+
+ program {
+ {DW_LNE_set_address main_label}
+ {line 1}
+ {DW_LNS_copy}
+
+ {DW_LNS_advance_pc 1}
+ {DW_LNE_end_sequence}
+
+ {DW_LNE_set_address 0}
+ {line 2}
+ {DW_LNS_copy}
+
+ {DW_LNS_advance_pc 1}
+ {DW_LNE_end_sequence}
+ }
+ }
+}
+
+if { [prepare_for_testing "failed to prepare" ${testfile} \
+ [list $srcfile $asm_file] {nodebug}] } {
+ return -1
+}
+
+if ![runto_main] {
+ return -1
+}
+
+gdb_test_multiple "maint info line-table" "END with address 1 eliminated" {
+ -re -wrap "END *0x0*1 Y \r\n.*" {
+ fail $gdb_test_name
+ }
+ -re -wrap "" {
+ pass $gdb_test_name
+ }
+}
^ permalink raw reply [flat|nested] 3+ messages in thread
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2021-01-04 13:59 [PATCH][gdb/symtab] Remove superfluous end-of-sequence marker Tom de Vries
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