Clean up 0-length handling in gdbpy_create_lazy_string_object

gdbpy_create_lazy_string_object will throw an exception if you pass it
a NULL pointer without also setting length=0 -- the default,
length==-1, will fail.  This seems bizarre.  Furthermore, it doesn't
make sense to do this check for array types, as an array can have a
zero length.  This patch cleans up the check and makes it specific to
TYPE_CODE_PTR.

diff --git a/gdb/python/py-lazy-string.c b/gdb/python/py-lazy-string.c
index 30a171d4c0b02c7db3e3b8e885b95a7c2dbe7e4e..1226c280174ac5c9c2c26f6bdf36508a5047a0ab 100644 (file)
--- a/gdb/python/py-lazy-string.c
+++ b/gdb/python/py-lazy-string.c
@@ -182,14 +182,6 @@ gdbpy_create_lazy_string_object (CORE_ADDR address, long length,
       return NULL;
     }
 
-  if (address == 0 && length != 0)
-    {
-      PyErr_SetString (gdbpy_gdb_memory_error,
-                      _("Cannot create a lazy string with address 0x0, " \
-                        "and a non-zero length."));
-      return NULL;
-    }
-
   if (!type)
     {
       PyErr_SetString (PyExc_RuntimeError,
@@ -216,6 +208,23 @@ gdbpy_create_lazy_string_object (CORE_ADDR address, long length,
          }
        break;
       }
+
+    case TYPE_CODE_PTR:
+      if (address == 0)
+       {
+         if (length > 0)
+           {
+             PyErr_SetString (gdbpy_gdb_memory_error,
+                              _("Cannot create a lazy string with address 0x0, " \
+                                "and a non-zero length."));
+             return nullptr;
+           }
+         length = 0;
+       }
+      break;
+
+    default:
+      gdb_assert_not_reached ("invalid type in gdbpy_create_lazy_string_object");
     }
 
   str_obj = PyObject_New (lazy_string_object, &lazy_string_object_type);

diff --git a/gdb/testsuite/gdb.python/py-lazy-string.exp b/gdb/testsuite/gdb.python/py-lazy-string.exp
index 0650c67d5e1cc75b00d2d3cb8d8ec3433979ee52..d212e613640bcbc01f40dd934e793ef5aff6ba05 100644 (file)
--- a/gdb/testsuite/gdb.python/py-lazy-string.exp
+++ b/gdb/testsuite/gdb.python/py-lazy-string.exp
@@ -48,6 +48,8 @@ gdb_test "python print(null.lazy_string(length=3).value())" \
 gdb_test "python print(null.lazy_string(length=-2))" \
     "ValueError.*: Invalid length.*Error occurred in Python.*" \
     "bad length"
+gdb_py_test_silent_cmd "python nullstr = null.lazy_string()" \
+    "create null lazy string with default length" 1
 
 foreach var_spec { { "ptr" "pointer" "const char \\*" -1 } \
                   { "array" "array" "const char \\[6\\]" 6 } \