Importing with ctypes in Python: fighting overflows

eryk sun eryksun at gmail.com
Tue Mar 7 09:11:38 EST 2017


On Tue, Mar 7, 2017 at 12:45 PM,  <borysova.mary at gmail.com> wrote:
> Importing with ctypes in Python: fighting overflows:
> https://www.cossacklabs.com/blog/fighting-ctypes-overflows.html

C int is 32-bit on all platforms currently supported by CPython --
both 32-bit and 64-bit. It's the default result type and the default
integer-argument conversion type in ctypes.

Since themis_status_t is a typedef for a C int, the proper way to
define the constant is as follows:

    >>> THEMIS_SCOMPARE_MATCH = ctypes.c_int(0xf0f0f0f0).value
    >>> THEMIS_SCOMPARE_MATCH
    -252645136

This has ctypes convert the value for you, which will be consistent
with how it converts a themis_status_t result.


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