Add explanatory comment for return_offset.

python · markshannon · Apr 13, 2023 · Apr 12, 2023 · Apr 12, 2023 · Apr 12, 2023
commit 18fad8020e81c83e5104a1bbf224b0673b351959
diff --git a/Include/internal/pycore_frame.h b/Include/internal/pycore_frame.h
@@ -61,6 +61,12 @@ typedef struct _PyInterpreterFrame {
    // over, or (in the case of a newly-created frame) a totally invalid value:
    _Py_CODEUNIT *prev_instr;
    int stacktop;  /* Offset of TOS from localsplus  */
+    /* The return_offset determines where a `RETURN` should go in the caller,
+     * relative to `prev_instr`.
+     * It is only meaningful to the callee,
+     * so it needs to be set in any CALL (to a Python function)
+     * or SEND (to a coroutine or generator).
+     * If there is no callee, then it is meaningless. */
    uint16_t return_offset;
    char owner;
    /* Locals and stack */