Merge pull request numpy#28862 from ngoldbaum/stringdtype-singleton-fixes

seberg · web-flow · commit 1672b69c9b0b · 2025-04-29T17:58:19.000+02:00
BUG: fix stringdtype singleton thread safety
diff --git a/numpy/_core/src/multiarray/stringdtype/dtype.c b/numpy/_core/src/multiarray/stringdtype/dtype.c
@@ -633,11 +633,16 @@ PyArray_Descr *
 stringdtype_finalize_descr(PyArray_Descr *dtype)
 {
     PyArray_StringDTypeObject *sdtype = (PyArray_StringDTypeObject *)dtype;
+    // acquire the allocator lock in case the descriptor we want to finalize
+    // is shared between threads, see gh-28813
+    npy_string_allocator *allocator = NpyString_acquire_allocator(sdtype);
     if (sdtype->array_owned == 0) {
         sdtype->array_owned = 1;
+        NpyString_release_allocator(allocator);
         Py_INCREF(dtype);
         return dtype;
     }
+    NpyString_release_allocator(allocator);
     PyArray_StringDTypeObject *ret = (PyArray_StringDTypeObject *)new_stringdtype_instance(
             sdtype->na_object, sdtype->coerce);
     ret->array_owned = 1;
@@ -850,14 +855,17 @@ init_string_dtype(void)
         return -1;
     }
 
-    PyArray_Descr *singleton =
-            NPY_DT_CALL_default_descr(&PyArray_StringDType);
+    PyArray_StringDTypeObject *singleton =
+            (PyArray_StringDTypeObject *)NPY_DT_CALL_default_descr(&PyArray_StringDType);
 
     if (singleton == NULL) {
         return -1;
     }
 
-    PyArray_StringDType.singleton = singleton;
+    // never associate the singleton with an array
+    singleton->array_owned = 1;
+
+    PyArray_StringDType.singleton = (PyArray_Descr *)singleton;
     PyArray_StringDType.type_num = NPY_VSTRING;
 
     for (int i = 0; PyArray_StringDType_casts[i] != NULL; i++) {
