RE: [Core] [new testcase] Regression 7.1->7.2 for iFort [Re: [RFA-v2] dwarf debug format: Support DW_AT_variable_parameter attribute]

Pierre Free Pascal
2010-11-04T08:47:13Z

Rereading the dwarf4 specifications,
I agree with Jan that I misinterpreted
this TAG and that it is only an information tag,
that could possibly be used as a warning notice
that we might modify caller variables.

Please apply this patch,
I will try to correct Free Pascal code generation
to cope for this issue.

Pierre Muller
Pascal language maintainer of GDB
and core team member of Free Pascal Compiler.

-----Message d'origine-----
De : core-bounces@freepascal.org [mailto:core-bounces@freepascal.org] De la
part de Jan Kratochvil
Envoyé : jeudi 4 novembre 2010 06:32
À : Pierre Muller
Cc : tromey@redhat.com; 'FPC Core Developer List';
gdb-patches@sourceware.org; 'Joel Brobecker'
Objet : [Core] [new testcase] Regression 7.1->7.2 for iFort [Re: [RFA-v2]
dwarf debug format: Support DW_AT_variable_parameter attribute]

On Fri, 21 May 2010 22:45:35 +0200, Pierre Muller wrote:
> Thanks, I committed the patch.

commit 570d5d01de35effada277a69552c0903a4928241
Author: Pierre Muller <muller@ics.u-strasbg.fr>
Date: Fri May 21 20:45:18 2010 +0000

* dwarf2read.c (new_symbol): Handle DW_AT_variable_parameter
attribute.

Please revert this patch.

From the DWARF-4 description of DW_AT_variable_parameter I do not think it
changes the data structures meaning in any way. It just states which data
can
be modified by whom. I do not think this is useful for GDB in any way.

> > I think it would be improved by a test case, but that is up to you.
>
> This test would be pascal specific anyhow,

I believe the Pascal compiler should generate different debug info. For the
`var' keyword you can either (a) use DW_TAG_reference_type and point
DW_AT_location at the pointer or (b) use DW_OP_deref (as iFort does) on the
passed pointer and point DW_AT_location at the value itself.
DW_AT_variable_parameter would be true only for the (a) choice.

1 subroutine f (i)
2 integer i
3 i = 2
4 end
5 program varparam
6 integer m
7 m = 1
8 call f (m)
9 write(*,*) m
10 end

for iFort 11.1 20100806 it regressed this code, GDB-7.1 displayed:

Breakpoint 1, f (i=1) at varparam.f90:3
3 i = 2
(gdb) p i
$1 = 1

while GDB-7.2 displays:

Breakpoint 2, f (i=@0x1) at varparam.f90:3
3 i = 2
(gdb) p i
$1 = (REF TO -> ( INTEGER(4) )) @0x1: <error reading variable>

(note that `0x1' GDB considers as an address here)

A new testcase for the iFort usage case is attached.

No regressions on {x86_64,x86_64-m32,i686}-fedora14snapshot-linux-gnu.

I will then check-in the testcase or you can or so.

Regards,
Jan

gdb/
2010-11-04 Jan Kratochvil <jan.kratochvil@redhat.com>

Revert:
2010-05-21 Pierre Muller <muller@ics.u-strasbg.fr>
* dwarf2read.c (new_symbol): Handle DW_AT_variable_parameter
attribute.

gdb/testsuite/
2010-11-04 Jan Kratochvil <jan.kratochvil@redhat.com>

* dw2-ifort-parameter-debug.S: New file.
* dw2-ifort-parameter.c: New file.
* dw2-ifort-parameter.exp: New file.

--- a/gdb/dwarf2read.c
+++ b/gdb/dwarf2read.c
@@ -10801,14 +10801,6 @@ new_symbol_full (struct die_info *die, struct type
*type, struct dwarf2_cu *cu,
{
dwarf2_const_value (attr, sym, cu);
}
- attr = dwarf2_attr (die, DW_AT_variable_parameter, cu);
- if (attr && DW_UNSND (attr))
- {
- struct type *ref_type;
-
- ref_type = lookup_reference_type (SYMBOL_TYPE (sym));
- SYMBOL_TYPE (sym) = ref_type;
- }

list_to_add = cu->list_in_scope;
break;
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/dw2-ifort-parameter-debug.S
@@ -0,0 +1,122 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+ Copyright 2010 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/>.
*/
+
+ .section .debug_info
+.Lcu1_begin:
+ /* CU header */
+ .4byte .Lcu1_end - .Lcu1_start /* Length of Compilation
Unit */
+.Lcu1_start:
+ .2byte 2 /* DWARF Version */
+ .4byte .Labbrev1_begin /* Offset into abbrev
section */
+ .byte 4 /* Pointer size */
+
+ /* CU die */
+ .uleb128 1 /* Abbrev:
DW_TAG_compile_unit */
+ .ascii "file1.txt\0" /* DW_AT_name */
+ .ascii "GNU C 3.3.3\0" /* DW_AT_producer */
+ .byte 1 /* DW_AT_language (C) */
+ .4byte func /* DW_AT_low_pc */
+ .4byte main /* DW_AT_high_pc */
+
+ .uleb128 2 /* Abbrev: DW_TAG_subprogram
*/
+ .byte 1 /* DW_AT_external */
+ .ascii "func\0" /* DW_AT_name */
+ .4byte func /* DW_AT_low_pc */
+ .4byte main /* DW_AT_high_pc */
+
+ .uleb128 3 /* Abbrev:
DW_TAG_formal_parameter */
+ .ascii "param\0" /* DW_AT_name */
+ .byte 1 /* DW_AT_variable_parameter
*/
+ .4byte .Ltype_int - .Lcu1_begin /* DW_AT_type */
+ .byte 2f - 1f /* DW_AT_location */
+1: .byte 3 /* DW_OP_addr */
+ .4byte ptr /* <addr> */
+ .byte 0x6 /* DW_OP_deref */
+2:
+
+ .byte 0 /* End of children of func
*/
+
+.Ltype_int:
+ .uleb128 4 /* Abbrev: DW_TAG_base_type
*/
+ .ascii "int\0" /* DW_AT_name */
+ .byte 4 /* DW_AT_byte_size */
+ .byte 5 /* DW_AT_encoding */
+
+ .byte 0 /* End of children of CU */
+.Lcu1_end:
+
+/* Abbrev table */
+ .section .debug_abbrev
+.Labbrev1_begin:
+ .uleb128 1 /* Abbrev code */
+ .uleb128 0x11 /* DW_TAG_compile_unit */
+ .byte 1 /* has_children */
+ .uleb128 0x3 /* DW_AT_name */
+ .uleb128 0x8 /* DW_FORM_string */
+ .uleb128 0x25 /* DW_AT_producer */
+ .uleb128 0x8 /* DW_FORM_string */
+ .uleb128 0x13 /* DW_AT_language */
+ .uleb128 0xb /* DW_FORM_data1 */
+ .uleb128 0x11 /* DW_AT_low_pc */
+ .uleb128 0x1 /* DW_FORM_addr */
+ .uleb128 0x12 /* DW_AT_high_pc */
+ .uleb128 0x1 /* DW_FORM_addr */
+ .byte 0x0 /* Terminator */
+ .byte 0x0 /* Terminator */
+
+ .uleb128 2 /* Abbrev code */
+ .uleb128 0x2e /* DW_TAG_subprogram */
+ .byte 1 /* has_children */
+ .uleb128 0x3f /* DW_AT_external */
+ .uleb128 0xc /* DW_FORM_flag */
+ .uleb128 0x3 /* DW_AT_name */
+ .uleb128 0x8 /* DW_FORM_string */
+ .uleb128 0x11 /* DW_AT_low_pc */
+ .uleb128 0x1 /* DW_FORM_addr */
+ .uleb128 0x12 /* DW_AT_high_pc */
+ .uleb128 0x1 /* DW_FORM_addr */
+ .byte 0x0 /* Terminator */
+ .byte 0x0 /* Terminator */
+
+ .uleb128 3 /* Abbrev code */
+ .uleb128 0x05 /* DW_TAG_formal_parameter
*/
+ .byte 0 /* has_children */
+ .uleb128 0x3 /* DW_AT_name */
+ .uleb128 0x8 /* DW_FORM_string */
+ .uleb128 0x4b /* DW_AT_variable_parameter
*/
+ .uleb128 0xb /* DW_FORM_data1 */
+ .uleb128 0x49 /* DW_AT_type */
+ .uleb128 0x13 /* DW_FORM_ref4 */
+ .uleb128 0x2 /* DW_AT_location */
+ .uleb128 0xa /* DW_FORM_block1 */
+ .byte 0x0 /* Terminator */
+ .byte 0x0 /* Terminator */
+
+ .uleb128 4 /* Abbrev code */
+ .uleb128 0x24 /* DW_TAG_base_type */
+ .byte 0 /* has_children */
+ .uleb128 0x3 /* DW_AT_name */
+ .uleb128 0x8 /* DW_FORM_string */
+ .uleb128 0xb /* DW_AT_byte_size */
+ .uleb128 0xb /* DW_FORM_data1 */
+ .uleb128 0x3e /* DW_AT_encoding */
+ .uleb128 0xb /* DW_FORM_data1 */
+ .byte 0x0 /* Terminator */
+ .byte 0x0 /* Terminator */
+
+ .byte 0x0 /* Terminator */
+ .byte 0x0 /* Terminator */
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/dw2-ifort-parameter.c
@@ -0,0 +1,31 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+ Copyright 2010 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/>.
*/
+
+int value = 0xdeadf00d;
+int *ptr = &value;
+
+void
+func (void)
+{
+}
+
+int
+main (void)
+{
+ func ();
+ return 0;
+}
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/dw2-ifort-parameter.exp
@@ -0,0 +1,40 @@
+# Copyright 2010 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/>.
+
+# Verify DW_AT_variable_parameter does not modify the data structures
meaning
+# for GDB, as being used by iFort.
+
+# This test can only be run on targets which support DWARF-2 and use gas.
+# For now pick a sampling of likely targets.
+if {![istarget *-*-linux*]
+ && ![istarget *-*-gnu*]
+ && ![istarget *-*-elf*]
+ && ![istarget *-*-openbsd*]
+ && ![istarget arm-*-eabi*]
+ && ![istarget powerpc-*-eabi*]} {
+ return 0
+}
+
+set testfile "dw2-ifort-parameter"
+
+if { [prepare_for_testing ${testfile}.exp ${testfile} [list ${testfile}.c
${testfile}-debug.S] {nodebug}] } {
+ return -1
+}
+
+if ![runto func] {
+ return -1
+}
+
+gdb_test "p/x param" " = 0xdeadf00d"
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