2010-04-08 Phil Muldoon <pmuldoon@redhat.com>

	PR python/11417

	* python/py-lazy-string.c (stpy_convert_to_value): Check for
          a NULL address.
	  (gdbpy_create_lazy_string_object): Allow strings with a NULL
          address and a zero length.

2010-04-08  Phil Muldoon  <pmuldoon@redhat.com>

	* gdb.python/py-value: Add null string variable.
	  (test_lazy_string): Test zero length, NULL address lazy
	  strings.

5 files changed, 32 insertions, 3 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 33f1556..05cfec6 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,12 @@
+2010-04-08  Phil Muldoon  <pmuldoon@redhat.com>
+
+	PR python/11417
+
+	* python/py-lazy-string.c (stpy_convert_to_value): Check for
+          a NULL address.
+	  (gdbpy_create_lazy_string_object): Allow strings with a NULL
+          address and a zero length.
+
 2010-04-08  Hui Zhu  <teawater@gmail.com>
 
 	* i386-tdep.c (i386_process_record): Add support for insn
diff --git a/gdb/python/py-lazy-string.c b/gdb/python/py-lazy-string.c
index 8309527..a2faa0e 100644
--- a/gdb/python/py-lazy-string.c
+++ b/gdb/python/py-lazy-string.c
@@ -94,6 +94,13 @@ stpy_convert_to_value  (PyObject *self, PyObject *args)
   lazy_string_object *self_string = (lazy_string_object *) self;
   struct value *val;
 
+  if (self_string->address == 0)
+    {
+      PyErr_SetString (PyExc_MemoryError,
+		       "Cannot create a value from NULL");
+      return NULL;
+    }
+
   val = value_at_lazy (self_string->type, self_string->address);
   return value_to_value_object (val);
 }
@@ -111,10 +118,11 @@ gdbpy_create_lazy_string_object (CORE_ADDR address, long length,
 {
   lazy_string_object *str_obj = NULL;
 
-  if (address == 0)
+  if (address == 0 && length != 0)
     {
       PyErr_SetString (PyExc_MemoryError,
-		       "Cannot create a lazy string from a GDB-side string.");
+		       _("Cannot create a lazy string with address 0x0, " \
+			 "and a non-zero length."));
       return NULL;
     }
 
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index b4a9dd92..2be54d7 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2010-04-08  Phil Muldoon  <pmuldoon@redhat.com>
+
+	* gdb.python/py-value: Add null string variable.
+	  (test_lazy_string): Test zero length, NULL address lazy
+	  strings.
+
 2010-04-07  H.J. Lu  <hongjiu.lu@intel.com>
 
 	* gdb.arch/i386-avx.c: New.
diff --git a/gdb/testsuite/gdb.python/py-value.c b/gdb/testsuite/gdb.python/py-value.c
index 80bc1e9..be933b3 100644
--- a/gdb/testsuite/gdb.python/py-value.c
+++ b/gdb/testsuite/gdb.python/py-value.c
@@ -59,7 +59,7 @@ main (int argc, char *argv[])
   int *p = a;
   int i = 2;
   int *ptr_i = &i;
-
+  const char *sn = 0;
   s.a = 3;
   s.b = 5;
   u.a = 7;
diff --git a/gdb/testsuite/gdb.python/py-value.exp b/gdb/testsuite/gdb.python/py-value.exp
index 2b18e02..3bfa173 100644
--- a/gdb/testsuite/gdb.python/py-value.exp
+++ b/gdb/testsuite/gdb.python/py-value.exp
@@ -267,6 +267,12 @@ proc test_lazy_strings {} {
   gdb_py_test_silent_cmd "python lstr = sptr.lazy_string()" "Aquire lazy string" 1
   gdb_test "python print lstr.type" "const char \*." "Test type name equality"
   gdb_test "python print sptr.type" "const char \*." "Test type name equality"
+  gdb_test "print sn" "0x0"
+  gdb_py_test_silent_cmd "python snptr = gdb.history (0)" "Get value from history" 1
+  gdb_test "python snstr = snptr.lazy_string(length=5)" ".*Cannot create a lazy string with address.*" "Test lazy string"
+  gdb_py_test_silent_cmd "python snstr = snptr.lazy_string(length=0)" "Succesfully create a lazy string" 1
+  gdb_test "python print snstr.length" "0" "Test lazy string length"
+  gdb_test "python print snstr.address" "0" "Test lazy string address"
 }