refactor alloc() logic

Author: picnixz

Modules/md5module.c

@@ -39,10 +39,7 @@ class MD5Type "MD5object *" "&PyType_Type"
 
 
 typedef struct {
-    PyObject_HEAD
-    // Prevents undefined behavior via multiple threads entering the C API.
-    bool use_mutex;
-    PyMutex mutex;
+    HASHLIB_OBJECT_HEAD
     Hacl_Hash_MD5_state_t *hash_state;
 } MD5object;
 
@@ -308,30 +305,20 @@ _md5_md5_impl(PyObject *module, PyObject *data, int usedforsecurity,
     }
 
     MD5object *new;
-    Py_buffer buf;
-
-    if (string) {
-        GET_BUFFER_VIEW_OR_ERROUT(string, &buf);
-    }
-
     MD5State *st = md5_get_state(module);
     if ((new = newMD5object(st)) == NULL) {
-        if (string) {
-            PyBuffer_Release(&buf);
-        }
         return NULL;
     }
 
     new->hash_state = Hacl_Hash_MD5_malloc();
     if (new->hash_state == NULL) {
         Py_DECREF(new);
-        if (string) {
-            PyBuffer_Release(&buf);
-        }
         return PyErr_NoMemory();
     }
 
     if (string) {
+        Py_buffer buf;
+        GET_BUFFER_VIEW_OR_ERROR(string, &buf, goto error);
         if (buf.len >= HASHLIB_GIL_MINSIZE) {
             /* We do not initialize self->lock here as this is the constructor
              * where it is not yet possible to have concurrent access. */
@@ -346,6 +333,10 @@ _md5_md5_impl(PyObject *module, PyObject *data, int usedforsecurity,
     }
 
     return (PyObject *)new;
+
+error:
+    Py_XDECREF(new);
+    return NULL;
 }