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" <pierre@freepascal.org>]

  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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