[RFA] Patch for PR gdb/2477

[ppluzhnikov at google dot com (Paul Pluzhnikov)]

Greetings,

Attached patch fixes error in printing NULL pointers when "set print object on".
 http://sourceware.org/cgi-bin/gnatsweb.pl?cmd=view&database=gdb&pr=2477
and adds a test case for it.

Ok to commit?

--
Paul Pluzhnikov


ChangeLog
2008-07-14  Paul Pluzhnikov  <ppluzhnikov@google.com>

	PR gdb/2477
	* cp-abi.c (value_virtual_fn_field): Handle NULL pointers.
	
testsuite/ChangeLog
2008-07-14  Paul Pluzhnikov  <ppluzhnikov@google.com>

	* gdb.cp/class2.exp, gdb.cp/class2.cc: Test for PR2477.
	
Index: cp-abi.c
===================================================================
RCS file: /cvs/src/src/gdb/cp-abi.c,v
retrieving revision 1.21
diff -u -p -u -r1.21 cp-abi.c
--- cp-abi.c	1 Jan 2008 22:53:09 -0000	1.21
+++ cp-abi.c	14 Jul 2008 17:23:56 -0000
@@ -89,7 +89,8 @@ value_virtual_fn_field (struct value **a
 struct type *
 value_rtti_type (struct value *v, int *full, int *top, int *using_enc)
 {
-  if ((current_cp_abi.rtti_type) == NULL)
+  if ((current_cp_abi.rtti_type) == NULL
+      || VALUE_ADDRESS (v) == 0)
     return NULL;
   return (*current_cp_abi.rtti_type) (v, full, top, using_enc);
 }
Index: testsuite/gdb.cp/class2.cc
===================================================================
RCS file: /cvs/src/src/gdb/testsuite/gdb.cp/class2.cc,v
retrieving revision 1.6
diff -u -p -u -r1.6 class2.cc
--- testsuite/gdb.cp/class2.cc	1 Jan 2008 22:53:19 -0000	1.6
+++ testsuite/gdb.cp/class2.cc	14 Jul 2008 17:23:56 -0000
@@ -41,6 +41,11 @@ B::~B()
   b2 = 902;
 }
 
+struct C : public B
+{
+  A *c1;
+};
+
 // Stop the compiler from optimizing away data.
 void refer (A *)
 {
@@ -57,16 +62,19 @@ void refer (empty *)
 
 int main (void)
 {
-  A alpha, *aap, *abp;
+  A alpha, *aap, *abp, *acp;
   B beta, *bbp;
+  C gamma;
   empty e;
 
   alpha.a1 = 100;
   beta.a1 = 200; beta.b1 = 201; beta.b2 = 202;
+  gamma.c1 = 0;
 
   aap = &alpha; refer (aap);
   abp = &beta;  refer (abp);
   bbp = &beta;  refer (bbp);
+  acp = &gamma; refer (acp);
   refer (&e);
 
   return 0;  // marker return 0
Index: testsuite/gdb.cp/class2.exp
===================================================================
RCS file: /cvs/src/src/gdb/testsuite/gdb.cp/class2.exp,v
retrieving revision 1.6
diff -u -p -u -r1.6 class2.exp
--- testsuite/gdb.cp/class2.exp	1 Jan 2008 22:53:19 -0000	1.6
+++ testsuite/gdb.cp/class2.exp	14 Jul 2008 17:23:56 -0000
@@ -117,3 +117,9 @@ gdb_test "print * (B *) abp" \
 # Printing the value of an object containing no data fields:
 
 gdb_test "p e" "= \{<No data fields>\}" "print object with no data fields"
+
+# Printing NULL pointers with "set print object on"
+
+gdb_test "set print object on" ""
+gdb_test "p acp" "= \\(C \\*\\) 0x\[a-f0-9\]+"
+gdb_test "p acp->c1" "\\(A \\*\\) 0x0"