Re: [RFA] Reference value coercion

Re: [RFA] Reference value coercion

[Paul Hilfinger]

Daniel,

> The patch is not right for C++.  It works for your test, because Child
> has a single base class, and therefore the values of the Child& and
> Parent& are the same; but in more complicated cases, this is no longer
> true.  The reference needs to be adjusted.

Yeah.  Somehow I knew it couldn't be that simple.

> Also, there's some trouble with the test case: using "runto" restarts
> the inferior, so runto_main followed by runto is redundant.  I think
> you just want to use runto.  The step_for_stub thing is ancient, and
> I don't think the testsuite works on systems that would require it any
> more.

Umm.  Well then you might want to look at ref-types.exp, from which I
stole most of this code.

...

> Does the attached work for Ada?

Yes, thanks, it does.

PNH

Re: [RFA] Reference value coercion

[Daniel Jacobowitz]

On Sat, May 20, 2006 at 06:10:14AM -0400, Paul Hilfinger wrote:
> Umm.  Well then you might want to look at ref-types.exp, from which I
> stole most of this code.

Yeah well.  Some of these tests just need to be rewritten; I'm not
volunteering.

> > Does the attached work for Ada?
> 
> Yes, thanks, it does.

I have belatedly committed this patch.  I retested it on
x86_64-pc-linux-gnu, since it was so long ago.

-- 
Daniel Jacobowitz
CodeSourcery

Re: [RFA] Reference value coercion

[Paul Hilfinger]

> > > Does the attached work for Ada?
> > 
> > Yes, thanks, it does.
> 
> I have belatedly committed this patch.  I retested it on
> x86_64-pc-linux-gnu, since it was so long ago.

Thanks, Daniel.

Paul Hilfinger

Re: [RFA] Reference value coercion

[Daniel Jacobowitz]

On Fri, Mar 31, 2006 at 05:28:26AM -0500, Paul Hilfinger wrote:
> at this point will eventually cause a segfault when f1 attempts to access
> a field of its argument.  This is because at the moment, since the type
> of C and the formal, P, differ, value_cast dereferences C.  This is
> a VERY bad idea generally in C++, for other reasons, but what's worse is
> that not only do we dereference C, but we then proceed to pass the 
> dereferenced value to f1 as if it were the address.  
> 
> The simple patch below to valops.c seems to solve this problem.  However,
> although I have presented this as a C++ problem, I naturally discovered it
> as an Ada problem, and it would be particularly good for a C++ person to
> consider whether other related changes to value_cast are in order.  
> 
> The patch also contains a suggested addition to the C++ testsuite.
> 
> Comments?

Hi Paul, and sorry for the delay.

The patch is not right for C++.  It works for your test, because Child
has a single base class, and therefore the values of the Child& and
Parent& are the same; but in more complicated cases, this is no longer
true.  The reference needs to be adjusted.

Also, there's some trouble with the test case: using "runto" restarts
the inferior, so runto_main followed by runto is redundant.  I think
you just want to use runto.  The step_for_stub thing is ancient, and
I don't think the testsuite works on systems that would require it any
more.

I enhanced the testcase to test that the reference was being properly
adjusted.

There's already code to do this for pointers (although it is
suspiciously simple and has a big FIXME in it...).  It's good enough
for the non-virtual case.

Does the attached work for Ada?

-- 
Daniel Jacobowitz
CodeSourcery

2006-05-05  Paul N. Hilfinger  <Hilfinger@adacore.com>
	    Daniel Jacobowitz  <dan@codesourcery.com>

	* infcall.c (value_arg_coerce): Use value_cast_pointers for
	references.  Avoid value_cast to a reference type.  Don't silently
	convert pointers to references.
	* valops.c (value_cast_pointers): New, based on value_cast.
	(value_cast): Use it.  Reject reference types.
	(value_ref): New.
	(typecmp): Use it.
	* value.h (value_cast_pointers, value_ref): New prototypes.

2006-05-05  Paul N. Hilfinger  <Hilfinger@adacore.com>
	    Daniel Jacobowitz  <dan@codesourcery.com>

	* gdb.cp/ref-params.exp: New test.
	* gdb.cp/ref-params.cc: New source file.
	* gdb.cp/Makefile.in (EXECUTABLES): Add ref-params.

Index: infcall.c
===================================================================
RCS file: /cvs/src/src/gdb/infcall.c,v
retrieving revision 1.74
diff -u -p -r1.74 infcall.c
--- infcall.c	17 Dec 2005 22:34:01 -0000	1.74
+++ infcall.c	5 May 2006 22:27:48 -0000
@@ -109,14 +109,20 @@ value_arg_coerce (struct value *arg, str
   switch (TYPE_CODE (type))
     {
     case TYPE_CODE_REF:
-      if (TYPE_CODE (arg_type) != TYPE_CODE_REF
-	  && TYPE_CODE (arg_type) != TYPE_CODE_PTR)
-	{
-	  arg = value_addr (arg);
-	  deprecated_set_value_type (arg, param_type);
-	  return arg;
-	}
-      break;
+      {
+	struct value *new_value;
+
+	if (TYPE_CODE (arg_type) == TYPE_CODE_REF)
+	  return value_cast_pointers (type, arg);
+
+	/* Cast the value to the reference's target type, and then
+	   convert it back to a reference.  This will issue an error
+	   if the value was not previously in memory - in some cases
+	   we should clearly be allowing this, but how?  */
+	new_value = value_cast (TYPE_TARGET_TYPE (type), arg);
+	new_value = value_ref (new_value);
+	return new_value;
+      }
     case TYPE_CODE_INT:
     case TYPE_CODE_CHAR:
     case TYPE_CODE_BOOL:
Index: valops.c
===================================================================
RCS file: /cvs/src/src/gdb/valops.c,v
retrieving revision 1.163
diff -u -p -r1.163 valops.c
--- valops.c	17 Dec 2005 22:34:03 -0000	1.163
+++ valops.c	5 May 2006 22:27:48 -0000
@@ -201,6 +201,70 @@ allocate_space_in_inferior (int len)
   return value_as_long (value_allocate_space_in_inferior (len));
 }
 
+/* Cast one pointer or reference type to another.  Both TYPE and
+   the type of ARG2 should be pointer types, or else both should be
+   reference types.  Returns the new pointer or reference.  */
+
+struct value *
+value_cast_pointers (struct type *type, struct value *arg2)
+{
+  struct type *type2 = check_typedef (value_type (arg2));
+  struct type *t1 = check_typedef (TYPE_TARGET_TYPE (type));
+  struct type *t2 = check_typedef (TYPE_TARGET_TYPE (type2));
+
+  if (TYPE_CODE (t1) == TYPE_CODE_STRUCT
+      && TYPE_CODE (t2) == TYPE_CODE_STRUCT
+      && !value_logical_not (arg2))
+    {
+      struct value *v;
+
+      /* Look in the type of the source to see if it contains the
+	 type of the target as a superclass.  If so, we'll need to
+	 offset the pointer rather than just change its type.  */
+      if (TYPE_NAME (t1) != NULL)
+	{
+	  struct value *v2;
+
+	  if (TYPE_CODE (type2) == TYPE_CODE_REF)
+	    v2 = coerce_ref (arg2);
+	  else
+	    v2 = value_ind (arg2);
+	  v = search_struct_field (type_name_no_tag (t1),
+				   v2, 0, t2, 1);
+	  if (v)
+	    {
+	      v = value_addr (v);
+	      deprecated_set_value_type (v, type);
+	      return v;
+	    }
+	}
+
+      /* Look in the type of the target to see if it contains the
+	 type of the source as a superclass.  If so, we'll need to
+	 offset the pointer rather than just change its type.
+	 FIXME: This fails silently with virtual inheritance.  */
+      if (TYPE_NAME (t2) != NULL)
+	{
+	  v = search_struct_field (type_name_no_tag (t2),
+				   value_zero (t1, not_lval), 0, t1, 1);
+	  if (v)
+	    {
+	      CORE_ADDR addr2 = value_as_address (arg2);
+	      addr2 -= (VALUE_ADDRESS (v)
+			+ value_offset (v)
+			+ value_embedded_offset (v));
+	      return value_from_pointer (type, addr2);
+	    }
+	}
+    }
+
+  /* No superclass found, just change the pointer type.  */
+  deprecated_set_value_type (arg2, type);
+  arg2 = value_change_enclosing_type (arg2, type);
+  set_value_pointed_to_offset (arg2, 0);	/* pai: chk_val */
+  return arg2;
+}
+
 /* Cast value ARG2 to type TYPE and return as a value.
    More general than a C cast: accepts any two types of the same length,
    and if ARG2 is an lvalue it can be cast into anything at all.  */
@@ -224,6 +288,10 @@ value_cast (struct type *type, struct va
   arg2 = coerce_ref (arg2);
   type2 = check_typedef (value_type (arg2));
 
+  /* You can't cast to a reference type.  See value_cast_pointers
+     instead.  */
+  gdb_assert (code1 != TYPE_CODE_REF);
+
   /* A cast to an undetermined-length array_type, such as (TYPE [])OBJECT,
      is treated like a cast to (TYPE [N])OBJECT,
      where N is sizeof(OBJECT)/sizeof(TYPE). */
@@ -369,50 +437,8 @@ value_cast (struct type *type, struct va
   else if (TYPE_LENGTH (type) == TYPE_LENGTH (type2))
     {
       if (code1 == TYPE_CODE_PTR && code2 == TYPE_CODE_PTR)
-	{
-	  struct type *t1 = check_typedef (TYPE_TARGET_TYPE (type));
-	  struct type *t2 = check_typedef (TYPE_TARGET_TYPE (type2));
-	  if (TYPE_CODE (t1) == TYPE_CODE_STRUCT
-	      && TYPE_CODE (t2) == TYPE_CODE_STRUCT
-	      && !value_logical_not (arg2))
-	    {
-	      struct value *v;
+	return value_cast_pointers (type, arg2);
 
-	      /* Look in the type of the source to see if it contains the
-	         type of the target as a superclass.  If so, we'll need to
-	         offset the pointer rather than just change its type.  */
-	      if (TYPE_NAME (t1) != NULL)
-		{
-		  v = search_struct_field (type_name_no_tag (t1),
-					   value_ind (arg2), 0, t2, 1);
-		  if (v)
-		    {
-		      v = value_addr (v);
-		      deprecated_set_value_type (v, type);
-		      return v;
-		    }
-		}
-
-	      /* Look in the type of the target to see if it contains the
-	         type of the source as a superclass.  If so, we'll need to
-	         offset the pointer rather than just change its type.
-	         FIXME: This fails silently with virtual inheritance.  */
-	      if (TYPE_NAME (t2) != NULL)
-		{
-		  v = search_struct_field (type_name_no_tag (t2),
-				       value_zero (t1, not_lval), 0, t1, 1);
-		  if (v)
-		    {
-                      CORE_ADDR addr2 = value_as_address (arg2);
-                      addr2 -= (VALUE_ADDRESS (v)
-                                + value_offset (v)
-                                + value_embedded_offset (v));
-                      return value_from_pointer (type, addr2);
-		    }
-		}
-	    }
-	  /* No superclass found, just fall through to change ptr type.  */
-	}
       deprecated_set_value_type (arg2, type);
       arg2 = value_change_enclosing_type (arg2, type);
       set_value_pointed_to_offset (arg2, 0);	/* pai: chk_val */
@@ -886,6 +912,22 @@ value_addr (struct value *arg1)
   return arg2;
 }
 
+/* Return a reference value for the object for which ARG1 is the contents.  */
+
+struct value *
+value_ref (struct value *arg1)
+{
+  struct value *arg2;
+
+  struct type *type = check_typedef (value_type (arg1));
+  if (TYPE_CODE (type) == TYPE_CODE_REF)
+    return arg1;
+
+  arg2 = value_addr (arg1);
+  deprecated_set_value_type (arg2, lookup_reference_type (type));
+  return arg2;
+}
+
 /* Given a value of a pointer type, apply the C unary * operator to it.  */
 
 struct value *
@@ -1106,7 +1148,7 @@ typecmp (int staticp, int varargs, int n
 	  if (TYPE_CODE (tt2) == TYPE_CODE_ARRAY)
 	    t2[i] = value_coerce_array (t2[i]);
 	  else
-	    t2[i] = value_addr (t2[i]);
+	    t2[i] = value_ref (t2[i]);
 	  continue;
 	}
 
Index: value.h
===================================================================
RCS file: /cvs/src/src/gdb/value.h,v
retrieving revision 1.91
diff -u -p -r1.91 value.h
--- value.h	31 Mar 2006 10:36:18 -0000	1.91
+++ value.h	5 May 2006 22:27:48 -0000
@@ -325,6 +325,8 @@ extern struct value *value_ind (struct v
 
 extern struct value *value_addr (struct value *arg1);
 
+extern struct value *value_ref (struct value *arg1);
+
 extern struct value *value_assign (struct value *toval,
 				   struct value *fromval);
 
@@ -367,6 +369,8 @@ extern struct type *value_rtti_target_ty
 extern struct value *value_full_object (struct value *, struct type *, int,
 					int, int);
 
+extern struct value *value_cast_pointers (struct type *, struct value *);
+
 extern struct value *value_cast (struct type *type, struct value *arg2);
 
 extern struct value *value_zero (struct type *type, enum lval_type lv);
Index: testsuite/gdb.cp/Makefile.in
===================================================================
RCS file: /cvs/src/src/gdb/testsuite/gdb.cp/Makefile.in,v
retrieving revision 1.1
diff -u -p -r1.1 Makefile.in
--- testsuite/gdb.cp/Makefile.in	23 Aug 2003 03:55:59 -0000	1.1
+++ testsuite/gdb.cp/Makefile.in	5 May 2006 22:27:49 -0000
@@ -3,7 +3,8 @@ srcdir = @srcdir@
 
 EXECUTABLES = ambiguous annota2 anon-union cplusfuncs cttiadd \
 	derivation inherit local member-ptr method misc \
-        overload ovldbreak ref-typ ref-typ2 templates userdef virtfunc namespace ref-types
+        overload ovldbreak ref-typ ref-typ2 templates userdef virtfunc namespace \
+	ref-types ref-params
 
 all info install-info dvi install uninstall installcheck check:
 	@echo "Nothing to be done for $@..."
Index: testsuite/gdb.cp/ref-params.cc
===================================================================
RCS file: testsuite/gdb.cp/ref-params.cc
diff -N testsuite/gdb.cp/ref-params.cc
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ testsuite/gdb.cp/ref-params.cc	5 May 2006 22:27:49 -0000
@@ -0,0 +1,80 @@
+/* This test script is part of GDB, the GNU debugger.
+
+   Copyright 2006
+   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 2 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, write to the Free Software
+   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+   */
+
+/* Author: Paul N. Hilfinger, AdaCore Inc. */
+
+struct Parent {
+  Parent (int id0) : id(id0) { }
+  int id;
+};
+
+struct Child : public Parent {
+  Child (int id0) : Parent(id0) { }
+};
+
+int f1(Parent& R)
+{
+  return R.id;			/* Set breakpoint marker3 here.  */
+}
+
+int f2(Child& C)
+{
+  return f1(C);			/* Set breakpoint marker2 here.  */
+}
+
+struct OtherParent {
+  OtherParent (int other_id0) : other_id(other_id0) { }
+  int other_id;
+};
+
+struct MultiChild : public Parent, OtherParent {
+  MultiChild (int id0) : Parent(id0), OtherParent(id0 * 2) { }
+};
+
+int mf1(OtherParent& R)
+{
+  return R.other_id;
+}
+
+int mf2(MultiChild& C)
+{
+  return mf1(C);
+}
+
+int main(void) 
+{
+  Child Q(42);
+  Child& QR = Q;
+
+  #ifdef usestubs
+     set_debug_traps();
+     breakpoint();
+  #endif
+
+  /* Set breakpoint marker1 here.  */
+
+  f2(Q);
+  f2(QR);
+
+  MultiChild MQ(53);
+  MultiChild& MQR = MQ;
+
+  mf2(MQ);			/* Set breakpoint MQ here.  */
+}
Index: testsuite/gdb.cp/ref-params.exp
===================================================================
RCS file: testsuite/gdb.cp/ref-params.exp
diff -N testsuite/gdb.cp/ref-params.exp
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ testsuite/gdb.cp/ref-params.exp	5 May 2006 22:27:49 -0000
@@ -0,0 +1,79 @@
+# Tests for reference parameters of types and their subtypes in GDB.
+# Copyright 2006 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 2 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, write to the Free Software
+# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  
+
+# written by Paul N. Hilfinger (Hilfinger@adacore.com)
+
+if $tracelevel then {
+        strace $tracelevel
+        }
+
+#
+# test running programs
+#
+set prms_id 0
+set bug_id 0
+
+if { [skip_cplus_tests] } { continue }
+
+set testfile "ref-params"
+set srcfile ${testfile}.cc
+set binfile ${objdir}/${subdir}/${testfile}
+
+if  { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable {debug c++}] != "" } {
+     gdb_suppress_entire_file "Testcase compile failed, so all tests in this file will automatically fail."
+}
+
+gdb_exit
+
+proc gdb_start_again { text } {
+    global srcdir
+    global subdir
+    global binfile
+    global srcfile
+
+    gdb_start
+    gdb_reinitialize_dir $srcdir/$subdir
+    gdb_load ${binfile}
+
+    runto ${srcfile}:[gdb_get_line_number $text]
+}
+
+gdb_start_again "marker1 here"
+gdb_test "print Q" ".*id = 42.*" "print value of a Child in main"
+gdb_test "print f1(Q)" ".* = 42.*" "print value of f1 on Child in main"
+gdb_test "print f2(Q)" ".* = 42.*" "print value of f2 on Child in main"
+
+gdb_start_again "marker1 here"
+gdb_test "print f1(QR)" ".* = 42.*" "print value of f1 on (Child&) in main"
+
+gdb_start_again "marker1 here"
+gdb_test "print f2(QR)" ".* = 42.*" "print value of f2 on (Child&) in main"
+
+gdb_start_again "marker2 here"
+gdb_test "print C" ".*id = 42.*" "print value of Child& in f2"
+gdb_test "print f1(C)" ".* = 42.*" "print value of f1 on Child& in f2"
+
+gdb_start_again "marker3 here"
+gdb_test "print R" ".*id = 42.*" "print value of Parent& in f1"
+
+gdb_start_again "breakpoint MQ here"
+gdb_test "print f1(MQ)" ".* = 53"
+gdb_test "print mf1(MQ)" ".* = 106"
+gdb_test "print mf2(MQ)" ".* = 106"
+gdb_test "print f1(MQR)" ".* = 53"
+gdb_test "print mf1(MQR)" ".* = 106"
+gdb_test "print mf2(MQR)" ".* = 106"

[RFA] Reference value coercion

[Paul Hilfinger]

Consider the following situation in C++:

    class Parent { ... };
    class Child : public Parent { ... };

    int f1 (Parent& P) { ... }

    int f2 (Child& C) { 
        // BP here
    }

where GDB is stopped at the point of the comment.  On (at least)
Linux with the most current GDB sources, the command

    (gdb) print f1(C)

at this point will eventually cause a segfault when f1 attempts to access
a field of its argument.  This is because at the moment, since the type
of C and the formal, P, differ, value_cast dereferences C.  This is
a VERY bad idea generally in C++, for other reasons, but what's worse is
that not only do we dereference C, but we then proceed to pass the 
dereferenced value to f1 as if it were the address.  

The simple patch below to valops.c seems to solve this problem.  However,
although I have presented this as a C++ problem, I naturally discovered it
as an Ada problem, and it would be particularly good for a C++ person to
consider whether other related changes to value_cast are in order.  

The patch also contains a suggested addition to the C++ testsuite.

Comments?

Paul Hilfinger


Changelog:

2006-03-31  Paul N. Hilfinger <Hilfinger@adacore.com>

	* valops.c (value_cast): If first argument is a reference type, do not
	apply coerce_ref to the second.

Testsuite Changelog:

2006-03-31  Paul N. Hilfinger <Hilfinger@adacore.com>

	* gdb.cp/ref-params.exp: New test.
	* gdb.cp/ref-params.cc: New source file.
	* gdb.cp/Makefile.in (EXECUTABLES): Add ref-params.

Index: current-public.148/gdb/valops.c
--- current-public.148/gdb/valops.c Wed, 21 Dec 2005 02:40:29 -0800 hilfingr (GdbPub/l/17_valops.c 1.1.1.24 644)
+++ submit.118(w)/gdb/valops.c Thu, 30 Mar 2006 23:54:34 -0800 hilfingr (GdbPub/l/17_valops.c 1.1.1.24.1.1 644)
@@ -221,7 +221,8 @@ value_cast (struct type *type, struct va
 
   CHECK_TYPEDEF (type);
   code1 = TYPE_CODE (type);
-  arg2 = coerce_ref (arg2);
+  if (code1 != TYPE_CODE_REF)
+    arg2 = coerce_ref (arg2);
   type2 = check_typedef (value_type (arg2));
 
   /* A cast to an undetermined-length array_type, such as (TYPE [])OBJECT,


Index: current-public.148/gdb/testsuite/gdb.cp/Makefile.in
--- current-public.148/gdb/testsuite/gdb.cp/Makefile.in Tue, 17 Jun 2003 02:27:41 -0700 hilfingr (GdbPub/J/36_Makefile.i 1.2 644)
+++ submit.118(w)/gdb/testsuite/gdb.cp/Makefile.in Thu, 30 Mar 2006 03:01:18 -0800 hilfingr (GdbPub/J/36_Makefile.i 1.3 644)
@@ -3,7 +3,8 @@ srcdir = @srcdir@
 
 EXECUTABLES = ambiguous annota2 anon-union cplusfuncs cttiadd \
 	derivation inherit local member-ptr method misc \
-        overload ovldbreak ref-typ ref-typ2 templates userdef virtfunc namespace ref-types
+        overload ovldbreak ref-typ ref-typ2 templates userdef virtfunc namespace \
+	ref-types ref-params
 
 all info install-info dvi install uninstall installcheck check:
 	@echo "Nothing to be done for $@..."
Index: current-public.148/gdb/testsuite/gdb.cp/ref-params.exp
--- current-public.148/gdb/testsuite/gdb.cp/ref-params.exp Fri, 31 Mar 2006 02:25:08 -0800 hilfingr ()
+++ submit.118(w)/gdb/testsuite/gdb.cp/ref-params.exp Thu, 30 Mar 2006 23:53:44 -0800 hilfingr (GdbPub/E/c/40_ref-params 1.1 644)
@@ -0,0 +1,93 @@
+# Tests for reference parameters of types and their subtypes in GDB.
+# Copyright 2006 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 2 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, write to the Free Software
+# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  
+
+# written by Paul N. Hilfinger (Hilfinger@adacore.com)
+
+if $tracelevel then {
+        strace $tracelevel
+        }
+
+#
+# test running programs
+#
+set prms_id 0
+set bug_id 0
+
+if { [skip_cplus_tests] } { continue }
+
+set testfile "ref-params"
+set srcfile ${testfile}.cc
+set binfile ${objdir}/${subdir}/${testfile}
+
+if  { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable {debug c++}] != "" } {
+     gdb_suppress_entire_file "Testcase compile failed, so all tests in this file will automatically fail."
+}
+
+gdb_exit
+gdb_start
+gdb_reinitialize_dir $srcdir/$subdir
+gdb_load ${binfile}
+
+proc get_to_mark { marker func } {
+    #
+    # set it up at a breakpoint so we can play with the variable values
+    #
+    if ![runto_main] then {
+	perror "couldn't run to breakpoint"
+	continue
+    }
+
+    if ![runto ${marker}] then {
+	perror "couldn't run to ${marker}"
+	continue
+    }
+
+    gdb_test "up" ".* ${func} .*" "up from ${marker}"
+}
+
+proc gdb_start_again { marker func } {
+    global srcdir
+    global subdir
+    global binfile
+    global gdb_prompt
+    global decimal
+
+    gdb_start
+    gdb_reinitialize_dir $srcdir/$subdir
+    gdb_load ${binfile}
+
+    get_to_mark ${marker} ${func}
+}
+
+get_to_mark marker1 main
+gdb_test "print Q" ".*id = 42.*" "print value of a Child in main"
+gdb_test "print f1(Q)" ".* = 42.*" "print value of f1 on Child in main"
+gdb_test "print f2(Q)" ".* = 42.*" "print value of f2 on Child in main"
+
+gdb_start_again marker1 main
+gdb_test "print f1(QR)" ".* = 42.*" "print value of f1 on (Child&) in main"
+
+gdb_start_again marker1 main
+gdb_test "print f2(QR)" ".* = 42.*" "print value of f2 on (Child&) in main"
+
+gdb_start_again marker2 f2
+gdb_test "print C" ".*id = 42.*" "print value of Child& in f2"
+gdb_test "print f1(C)" ".* = 42.*" "print value of f1 on Child& in f2"
+
+gdb_start_again marker3 f1
+gdb_test "print R" ".*id = 42.*" "print value of Parent& in f1"
+
Index: current-public.148/gdb/testsuite/gdb.cp/ref-params.cc
--- current-public.148/gdb/testsuite/gdb.cp/ref-params.cc Fri, 31 Mar 2006 02:25:08 -0800 hilfingr ()
+++ submit.118(w)/gdb/testsuite/gdb.cp/ref-params.cc Fri, 31 Mar 2006 02:24:09 -0800 hilfingr (GdbPub/E/c/41_ref-params 1.1 644)
@@ -0,0 +1,73 @@
+/* This test script is part of GDB, the GNU debugger.
+
+   Copyright 2006
+   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 2 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, write to the Free Software
+   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+   */
+
+/* Author: Paul N. Hilfinger, AdaCore Inc. */
+
+struct Parent {
+  Parent (int id0) : id(id0) { }
+  int id;
+};
+
+struct Child : public Parent {
+  Child (int id0) : Parent(id0) { }
+};
+
+void marker1 (void)
+{
+
+}
+
+void marker2 (void)
+{
+
+}
+
+void marker3 (void)
+{
+
+}
+
+int f1(Parent& R)
+{
+  marker3();
+  return R.id;
+}
+
+int f2(Child& C)
+{
+  marker2();
+  return f1(C);
+}
+
+int main(void) 
+{
+  Child Q(42);
+  Child& QR = Q;
+
+  #ifdef usestubs
+     set_debug_traps();
+     breakpoint();
+  #endif
+  marker1();
+
+  f2(Q);
+  f2(QR);
+}
+