fix reference counting issues in asciidtype and metadatadtype

asciidtype/asciidtype/src/dtype.c

@@ -55,20 +55,20 @@ new_asciidtype_instance(long size)
 }
 
 /*
- * This is used to determine the correct dtype to return when operations mix
- * dtypes (I think?). For now just return the first one.
+ * This is used to determine the correct dtype to return when dealing
+ * with a mix of different dtypes (for example when creating an array
+ * from a list of scalars). Always return the dtype with the biggest
+ * size.
  */
 static ASCIIDTypeObject *
 common_instance(ASCIIDTypeObject *dtype1, ASCIIDTypeObject *dtype2)
 {
-    if (!PyObject_RichCompareBool((PyObject *)dtype1, (PyObject *)dtype2,
-                                  Py_EQ)) {
-        PyErr_SetString(
-                PyExc_RuntimeError,
-                "common_instance called on unequal ASCIIDType instances");
-        return NULL;
+    if (dtype1->size >= dtype2->size) {
+        Py_INCREF(dtype1);
+        return dtype1;
     }
-    return dtype1;
+    Py_INCREF(dtype2);
+    return dtype2;
 }
 
 static PyArray_DTypeMeta *

asciidtype/tests/test_asciidtype.py

@@ -24,6 +24,15 @@ def test_creation_with_explicit_dtype():
     )
 
 
+def test_creation_from_scalar():
+    data = [
+        ASCIIScalar("hello", ASCIIDType(6)),
+        ASCIIScalar("array", ASCIIDType(7)),
+    ]
+    arr = np.array(data)
+    assert repr(arr) == ("array(['hello', 'array'], dtype=ASCIIDType(7))")
+
+
 def test_creation_truncation():
     inp = ["hello", "this", "is", "an", "array"]
 

metadatadtype/metadatadtype/src/dtype.c

@@ -52,6 +52,7 @@ get_metadata(PyObject *scalar)
     }
 
     PyObject *metadata = dtype->metadata;
+    Py_DECREF(dtype);
     if (metadata == NULL) {
         return NULL;
     }
@@ -87,6 +88,7 @@ new_metadatadtype_instance(PyObject *metadata)
 static MetadataDTypeObject *
 common_instance(MetadataDTypeObject *dtype1, MetadataDTypeObject *dtype2)
 {
+    Py_INCREF(dtype1);
     return dtype1;
 }