Misleading warnings: "local variable referenced before assignment"

[nikratio]

Starting with Cython 0.15, constructions like

def setxattr(path, name, value):
    '''Set extended attribute'''

    cdef int ret
    cdef Py_ssize_t len_
    cdef char *cvalue, *cname, *cpath

    PyBytes_AsStringAndSize(value, &cvalue, &len_)
    #...

produce warnings of the form

warning: /home/nikratio/projekte/llfuse/src/fuse_api.pxi:58:42: local variable 'cvalue' referenced before assignment
warning: /home/nikratio/projekte/llfuse/src/fuse_api.pxi:58:49: local variable 'len_' referenced before assignment

...but obviously the code is correct. I'm not sure if warning about uninitialized values when one just passes a pointer to that variable really catches more bugs than it produces false positives.

[vitja]

I'm not sure how to fix this correctly. First idea is: mark names with ampersand as safe.

• &a - we just take address of a
• &a[0] - this is unsafe

[vitja]

Fixed here  https://github.com/cython/cython/commit/2439267df3741155a4ceae9249b748e8ecd5e04c

[nikratio]

I don't think this has been fixed completely:

$ cython -Wextra mylib.pyx
warning: mylib.pyx:7:13: local variable 'i' might be referenced before assignment

$ cat mylib.pyx 
cdef extern from "*":
    void init_i(int* i)

cdef test():
    cdef int i

    init_i(&i)

$ cython --version
Cython version 0.15.1