except ? not recognized by this plugin

[irvinren]

according to the documentation of Cython @ https://cython.readthedocs.io/en/latest/src/userguide/language_basics.html#error-return-values, the syntax of except? should be recognized as a way to specify the exception value, whereas the syntax is not recognized and the following code is regarded as a syntax error .

Please help fix.

from libc.limits cimport INT_MAX

cpdef int test_func(int input) except ?INT_MAX: return 1

thanks

Xiquan Ren

[irvinren]

the original explanation of the syntax is

Error return values

In Python (more specifically, in the CPython runtime), exceptions that occur inside of a function are signaled to the caller and propagated up the call stack through defined error return values. For functions that return a Python object (and thus, a pointer to such an object), the error return value is simply the NULL pointer, so any function returning a Python object has a well-defined error return value.

While this is always the case for Python functions, functions defined as C functions or cpdef/@ccall functions can return arbitrary C types, which do not have such a well-defined error return value. By default Cython uses a dedicated return value to signal that an exception has been raised from non-external cpdef/@ccall functions. However, how Cython handles exceptions from these functions can be changed if needed.

A cdef function may be declared with an exception return value for it as a contract with the caller. Here is an example:

cdef int spam() except -1: ...

With this declaration, whenever an exception occurs inside spam, it will immediately return with the value -1. From the caller’s side, whenever a call to spam returns -1, the caller will assume that an exception has occurred and can now process or propagate it. Calling spam() is roughly translated to the following C code

[irvinren]

If all possible return values are legal and you can’t reserve one entirely for signalling errors, you can use an alternative form of exception value declaration

cdef int spam() except? -1: ...

The ? indicates that the value -1 may signal an error.

In this case, Cython generates a call to PyErr_Occurred() if the exception value is returned, to make sure it really received an exception and not just a normal result. Calling spam() is roughly translated to the following C code:

ret_val = spam(); if (ret_val == -1 && PyErr_Occurred()) goto error_handler;

There is also a third form of exception value declaration