Revert "pythongh-140067: Fix memory leak in sub-interpreter creation (python#140111)" (python#140140)

This reverts commit 59547a2.

Author: ZeroIntensity

Include/internal/pycore_interp_structs.h

@@ -769,6 +769,12 @@ struct _is {
      * and should be placed at the beginning. */
     struct _ceval_state ceval;
 
+    /* This structure is carefully allocated so that it's correctly aligned
+     * to avoid undefined behaviors during LOAD and STORE. The '_malloced'
+     * field stores the allocated pointer address that will later be freed.
+     */
+    void *_malloced;
+
     PyInterpreterState *next;
 
     int64_t id;

Misc/NEWS.d/next/Core_and_Builtins/2025-10-14-17-07-37.gh-issue-140067.ID2gOm.rst

@@ -457,19 +457,16 @@ _PyInterpreterState_Enable(_PyRuntimeState *runtime)
 static PyInterpreterState *
 alloc_interpreter(void)
 {
-    // Aligned allocation for PyInterpreterState.
-    // the first word of the memory block is used to store
-    // the original pointer to be used later to free the memory.
     size_t alignment = _Alignof(PyInterpreterState);
-    size_t allocsize = sizeof(PyInterpreterState) + sizeof(void *) + alignment - 1;
+    size_t allocsize = sizeof(PyInterpreterState) + alignment - 1;
     void *mem = PyMem_RawCalloc(1, allocsize);
     if (mem == NULL) {
         return NULL;
     }
-    void *ptr = _Py_ALIGN_UP((char *)mem + sizeof(void *), alignment);
-    ((void **)ptr)[-1] = mem;
-    assert(_Py_IS_ALIGNED(ptr, alignment));
-    return ptr;
+    PyInterpreterState *interp = _Py_ALIGN_UP(mem, alignment);
+    assert(_Py_IS_ALIGNED(interp, alignment));
+    interp->_malloced = mem;
+    return interp;
 }
 
 static void
@@ -484,7 +481,7 @@ free_interpreter(PyInterpreterState *interp)
             interp->obmalloc = NULL;
         }
         assert(_Py_IS_ALIGNED(interp, _Alignof(PyInterpreterState)));
-        PyMem_RawFree(((void **)interp)[-1]);
+        PyMem_RawFree(interp->_malloced);
     }
 }