Fix various python lazy string bugs.

gdb/ChangeLog:

	PR python/17728, python/18439, python/18779
	* python/py-lazy-string.c (lazy_string_object): Clarify use of LENGTH
	member.  Change type of TYPE member to PyObject *.  All uses updated.
	(stpy_convert_to_value): Fix handling of TYPE_CODE_PTR.
	(gdbpy_create_lazy_string_object): Flag bad length values.
	Handle TYPE_CODE_ARRAY with possibly different user-provided length.
	Handle typedefs in incoming type.
	(stpy_lazy_string_elt_type): New function.
	(gdbpy_extract_lazy_string): Call it.
	* python/py-value.c (valpy_lazy_string): Flag bad length values.
	Fix handling of TYPE_CODE_PTR.  Handle TYPE_CODE_ARRAY.  Handle
	typedefs in incoming type.

gdb/testsuite/ChangeLog:

	PR python/17728, python/18439, python/18779
	* gdb.python/py-value.c (main) Delete locals sptr, sn.
	* gdb.python/py-lazy-string.c (pointer): New typedef.
	(main): New locals ptr, array, typedef_ptr.
	* gdb.python/py-value.exp: Move lazy string tests to ...
	* gdb.python/py-lazy-string.exp: ... here.  Add more tests for pointer,
	array, typedef lazy strings.

2 files changed, 172 insertions, 21 deletions

diff --git a/gdb/python/py-lazy-string.c b/gdb/python/py-lazy-string.c
index 4af4566ef64..ab3f4117439 100644
--- a/gdb/python/py-lazy-string.c
+++ b/gdb/python/py-lazy-string.c
@@ -26,6 +26,7 @@
 
 typedef struct {
   PyObject_HEAD
+
   /*  Holds the address of the lazy string.  */
   CORE_ADDR address;
 
@@ -35,14 +36,21 @@ typedef struct {
       encoding when the sting is printed.  */
   char *encoding;
 
-  /* Holds the length of the string in characters.  If the
-     length is -1, then the string will be fetched and encoded up to
-     the first null of appropriate width.  */
+  /* If TYPE is an array: If the length is known, then this value is the
+     array's length, otherwise it is -1.
+     If TYPE is not an array: Then this value represents the string's length.
+     In either case, if the value is -1 then the string will be fetched and
+     encoded up to the first null of appropriate width.  */
   long length;
 
-  /*  This attribute holds the type that is represented by the lazy
-      string's type.  */
-  struct type *type;
+  /* This attribute holds the type of the string.
+     For example if the lazy string was created from a C "char*" then TYPE
+     represents a C "char*".
+     To get the type of the character in the string call
+     stpy_lazy_string_elt_type.
+     This is recorded as a PyObject so that we take advantage of support for
+     preserving the type should its owning objfile go away.  */
+  PyObject *type;
 } lazy_string_object;
 
 extern PyTypeObject lazy_string_object_type
@@ -88,11 +96,12 @@ stpy_get_type (PyObject *self, void *closure)
 {
   lazy_string_object *str_obj = (lazy_string_object *) self;
 
-  return type_to_type_object (str_obj->type);
+  Py_INCREF (str_obj->type);
+  return str_obj->type;
 }
 
 static PyObject *
-stpy_convert_to_value  (PyObject *self, PyObject *args)
+stpy_convert_to_value (PyObject *self, PyObject *args)
 {
   lazy_string_object *self_string = (lazy_string_object *) self;
   struct value *val = NULL;
@@ -106,7 +115,32 @@ stpy_convert_to_value  (PyObject *self, PyObject *args)
 
   TRY
     {
-      val = value_at_lazy (self_string->type, self_string->address);
+      struct type *type = type_object_to_type (self_string->type);
+      struct type *realtype;
+
+      gdb_assert (type != NULL);
+      realtype = check_typedef (type);
+      switch (TYPE_CODE (realtype))
+	{
+	case TYPE_CODE_PTR:
+	  /* If a length is specified we need to convert this to an array
+	     of the specified size.  */
+	  if (self_string->length != -1)
+	    {
+	      /* PR 20786: There's no way to specify an array of length zero.
+		 Record a length of [0,-1] which is how Ada does it.  Anything
+		 we do is broken, but this is one possible solution.  */
+	      type = lookup_array_range_type (TYPE_TARGET_TYPE (realtype),
+					      0, self_string->length - 1);
+	      val = value_at_lazy (type, self_string->address);
+	    }
+	  else
+	    val = value_from_pointer (type, self_string->address);
+	  break;
+	default:
+	  val = value_at_lazy (type, self_string->address);
+	  break;
+	}
     }
   CATCH (except, RETURN_MASK_ALL)
     {
@@ -125,11 +159,24 @@ stpy_dealloc (PyObject *self)
   xfree (self_string->encoding);
 }
 
+/* Low level routine to create a <gdb.LazyString> object.
+
+   Note: If TYPE is an array, LENGTH either must be -1 (meaning to use the
+   size of the array, which may itself be unknown in which case a length of
+   -1 is still used) or must be the length of the array.  */
+
 PyObject *
 gdbpy_create_lazy_string_object (CORE_ADDR address, long length,
-			   const char *encoding, struct type *type)
+				 const char *encoding, struct type *type)
 {
   lazy_string_object *str_obj = NULL;
+  struct type *realtype;
+
+  if (length < -1)
+    {
+      PyErr_SetString (PyExc_ValueError, _("Invalid length."));
+      return NULL;
+    }
 
   if (address == 0 && length != 0)
     {
@@ -146,6 +193,27 @@ gdbpy_create_lazy_string_object (CORE_ADDR address, long length,
       return NULL;
     }
 
+  realtype = check_typedef (type);
+  switch (TYPE_CODE (realtype))
+    {
+    case TYPE_CODE_ARRAY:
+      {
+	LONGEST array_length = -1;
+	LONGEST low_bound, high_bound;
+
+	if (get_array_bounds (realtype, &low_bound, &high_bound))
+	  array_length = high_bound - low_bound + 1;
+	if (length == -1)
+	  length = array_length;
+	else if (length != array_length)
+	  {
+	    PyErr_SetString (PyExc_ValueError, _("Invalid length."));
+	    return NULL;
+	  }
+	break;
+      }
+    }
+
   str_obj = PyObject_New (lazy_string_object, &lazy_string_object_type);
   if (!str_obj)
     return NULL;
@@ -156,7 +224,7 @@ gdbpy_create_lazy_string_object (CORE_ADDR address, long length,
     str_obj->encoding = NULL;
   else
     str_obj->encoding = xstrdup (encoding);
-  str_obj->type = type;
+  str_obj->type = type_to_type_object (type);
 
   return (PyObject *) str_obj;
 }
@@ -179,12 +247,35 @@ gdbpy_is_lazy_string (PyObject *result)
   return PyObject_TypeCheck (result, &lazy_string_object_type);
 }
 
+/* Return the type of a character in lazy string LAZY.  */
+
+static struct type *
+stpy_lazy_string_elt_type (lazy_string_object *lazy)
+{
+  struct type *type = type_object_to_type (lazy->type);
+  struct type *realtype;
+
+  gdb_assert (type != NULL);
+  realtype = check_typedef (type);
+
+  switch (TYPE_CODE (realtype))
+    {
+    case TYPE_CODE_PTR:
+    case TYPE_CODE_ARRAY:
+      return TYPE_TARGET_TYPE (realtype);
+    default:
+      /* This is done to preserve existing behaviour.  PR 20769.
+	 E.g., gdb.parse_and_eval("my_int_variable").lazy_string().type.  */
+      return realtype;
+    }
+}
+
 /* Extract the parameters from the lazy string object STRING.
    ENCODING may be set to NULL, if no encoding is found.  */
 
 void
 gdbpy_extract_lazy_string (PyObject *string, CORE_ADDR *addr,
-			   struct type **str_type,
+			   struct type **str_elt_type,
 			   long *length,
 			   gdb::unique_xmalloc_ptr<char> *encoding)
 {
@@ -195,7 +286,7 @@ gdbpy_extract_lazy_string (PyObject *string, CORE_ADDR *addr,
   lazy = (lazy_string_object *) string;
 
   *addr = lazy->address;
-  *str_type = lazy->type;
+  *str_elt_type = stpy_lazy_string_elt_type (lazy);
   *length = lazy->length;
   encoding->reset (lazy->encoding ? xstrdup (lazy->encoding) : NULL);
 }
diff --git a/gdb/python/py-value.c b/gdb/python/py-value.c
index eb3d307b19b..124d3980139 100644
--- a/gdb/python/py-value.c
+++ b/gdb/python/py-value.c
@@ -400,9 +400,19 @@ valpy_get_dynamic_type (PyObject *self, void *closure)
    A lazy string is a pointer to a string with an optional encoding and
    length.  If ENCODING is not given, encoding is set to None.  If an
    ENCODING is provided the encoding parameter is set to ENCODING, but
-   the string is not encoded.  If LENGTH is provided then the length
-   parameter is set to LENGTH, otherwise length will be set to -1 (first
-   null of appropriate with).  */
+   the string is not encoded.
+   If LENGTH is provided then the length parameter is set to LENGTH.
+   Otherwise if the value is an array of known length then the array's length
+   is used.  Otherwise the length will be set to -1 (meaning first null of
+   appropriate with).
+
+   Note: In order to not break any existing uses this allows creating
+   lazy strings from anything.  PR 20769.  E.g.,
+   gdb.parse_and_eval("my_int_variable").lazy_string().
+   "It's easier to relax restrictions than it is to impose them after the
+   fact."  So we should be flagging any unintended uses as errors, but it's
+   perhaps too late for that.  */
+
 static PyObject *
 valpy_lazy_string (PyObject *self, PyObject *args, PyObject *kw)
 {
@@ -416,16 +426,66 @@ valpy_lazy_string (PyObject *self, PyObject *args, PyObject *kw)
 				    &user_encoding, &length))
     return NULL;
 
+  if (length < -1)
+    {
+      PyErr_SetString (PyExc_ValueError, _("Invalid length."));
+      return NULL;
+    }
+
   TRY
     {
       scoped_value_mark free_values;
+      struct type *type, *realtype;
+      CORE_ADDR addr;
 
-      if (TYPE_CODE (value_type (value)) == TYPE_CODE_PTR)
-	value = value_ind (value);
+      type = value_type (value);
+      realtype = check_typedef (type);
+
+      switch (TYPE_CODE (realtype))
+	{
+	case TYPE_CODE_ARRAY:
+	  {
+	    LONGEST array_length = -1;
+	    LONGEST low_bound, high_bound;
+
+	    /* PR 20786: There's no way to specify an array of length zero.
+	       Record a length of [0,-1] which is how Ada does it.  Anything
+	       we do is broken, but this one possible solution.  */
+	    if (get_array_bounds (realtype, &low_bound, &high_bound))
+	      array_length = high_bound - low_bound + 1;
+	    if (length == -1)
+	      length = array_length;
+	    else if (array_length == -1)
+	      {
+		type = lookup_array_range_type (TYPE_TARGET_TYPE (realtype),
+						0, length - 1);
+	      }
+	    else if (length != array_length)
+	      {
+		/* We need to create a new array type with the
+		   specified length.  */
+		if (length > array_length)
+		  error (_("Length is larger than array size."));
+		type = lookup_array_range_type (TYPE_TARGET_TYPE (realtype),
+						low_bound,
+						low_bound + length - 1);
+	      }
+	    addr = value_address (value);
+	    break;
+	  }
+	case TYPE_CODE_PTR:
+	  /* If a length is specified we defer creating an array of the
+	     specified width until we need to.  */
+	  addr = value_as_address (value);
+	  break;
+	default:
+	  /* Should flag an error here.  PR 20769.  */
+	  addr = value_address (value);
+	  break;
+	}
 
-      str_obj = gdbpy_create_lazy_string_object (value_address (value), length,
-						 user_encoding,
-						 value_type (value));
+      str_obj = gdbpy_create_lazy_string_object (addr, length, user_encoding,
+						 type);
     }
   CATCH (except, RETURN_MASK_ALL)
     {