ceval.c

on_error:
        if (why == WHY_NOT) {
            if (err == 0 && x != NULL) {
                    continue; /* Normal, fast path */
            }
            why = WHY_EXCEPTION;
            x = Py_None;
            err = 0;
        }
        /* Double-check exception status */
        if (why == WHY_EXCEPTION || why == WHY_RERAISE) {
            if (!PyErr_Occurred()) {
                PyErr_SetString(PyExc_SystemError,
                    "error return without exception set");
                why = WHY_EXCEPTION;
            }
        }
        /* Log traceback info if this is a real exception */
        if (why == WHY_EXCEPTION) {
            PyTraceBack_Here(f);
            if (tstate->c_tracefunc != NULL)
                call_exc_trace(tstate->c_tracefunc,
                               tstate->c_traceobj, f);
        }
        /* For the rest, treat WHY_RERAISE as WHY_EXCEPTION */
        if (why == WHY_RERAISE)
            why = WHY_EXCEPTION;
fast_block_end:
        while (why != WHY_NOT && f->f_iblock > 0) {
            /* Peek at the current block. */
            PyTryBlock *b = &f->f_blockstack[f->f_iblock - 1];

            assert(why != WHY_YIELD);
            if (b->b_type == SETUP_LOOP && why == WHY_CONTINUE) {
                why = WHY_NOT;
                JUMPTO(PyInt_AS_LONG(retval));
                Py_DECREF(retval);
                break;
            }

            /* Now we have to pop the block. */
            f->f_iblock--;

            while (STACK_LEVEL() > b->b_level) {
                v = POP();
                Py_XDECREF(v);
            }
            if (b->b_type == SETUP_LOOP && why == WHY_BREAK) {
                why = WHY_NOT;
                JUMPTO(b->b_handler);
                break;
            }
            if (b->b_type == SETUP_FINALLY ||
                (b->b_type == SETUP_EXCEPT &&
                 why == WHY_EXCEPTION) ||
                b->b_type == SETUP_WITH) {
                if (why == WHY_EXCEPTION) {
                    PyObject *exc, *val, *tb;
                    PyErr_Fetch(&exc, &val, &tb);
                    if (val == NULL) {
                        val = Py_None;
                        Py_INCREF(val);
                    }
                    /* Make the raw exception data
                       available to the handler,
                       so a program can emulate the
                       Python main loop.  Don't do
                       this for 'finally'. */
                    if (b->b_type == SETUP_EXCEPT ||
                        b->b_type == SETUP_WITH) {
                        PyErr_NormalizeException(
                            &exc, &val, &tb);
                        set_exc_info(tstate,
                                     exc, val, tb);
                    }
                    if (tb == NULL) {
                        Py_INCREF(Py_None);
                        PUSH(Py_None);
                    } else
                        PUSH(tb);
                    PUSH(val);
                    PUSH(exc);
                }
                else {
                    if (why & (WHY_RETURN | WHY_CONTINUE))
                        PUSH(retval);
                    v = PyInt_FromLong((long)why);
                    PUSH(v);
                }
                why = WHY_NOT;
                JUMPTO(b->b_handler);
                break;
            }
        } /* unwind stack */
        /* End the loop if we still have an error (or return) */
        if (why != WHY_NOT)
            break;
    } /* main loop */