pythongh-99633: _contextvars: Clarify that the ref is stolen, not borrowed

rhansen · rhansen · commit 11c500b21097 · 2024-10-10T04:42:33.000-04:00
Improve readability by moving destination assignment next to source
reset, and comment that the ref is stolen.
diff --git a/Python/context.c b/Python/context.c
@@ -202,9 +202,8 @@ _PyContext_Enter(PyThreadState *ts, PyContext *ctx)
         return -1;
     }
 
-    ctx->ctx_prev = ts->context;  /* borrow */
     ctx->ctx_entered = 1;
-
+    ctx->ctx_prev = ts->context;  /* steal */
     ts->context = Py_NewRef(ctx);
     context_switched(ts);
     return 0;
@@ -238,8 +237,7 @@ _PyContext_Exit(PyThreadState *ts, PyContext *ctx)
         return -1;
     }
 
-    Py_SETREF(ts->context, ctx->ctx_prev);
-
+    Py_SETREF(ts->context, ctx->ctx_prev);  /* steal */
     ctx->ctx_prev = NULL;
     ctx->ctx_entered = 0;
     context_switched(ts);
