gistfile1.py

import cffi


isdefined_template = """
#include <openssl/opensslconf.h>
char cryptography_isdefined_{0}() {{
#ifdef {0}
    return 1;
#else
    return 0;
#endif
}}
"""


def isdefined(define):
    func_name = "cryptography_isdefined_{0}".format(define)
    ffi = cffi.FFI()
    ffi.cdef("bool {0}();".format(func_name))
    source = isdefined_template.format(define)
    lib = ffi.verify(source=source)
    return getattr(lib, func_name)()