I am using Python and CFFI to write some unit tests for a library that I have written in C, this library involves socket programming on Linux. The .c file is compiled into a shared library and then loaded using ffi.dlopen().
Naturally the struct sockaddr_in structure is used which is defined in netinet/in.h, and in my case it is used within another structure.
typedef struct sDeviceSockAddr
{
int sockfd;
struct sockaddr_in deviceAddr;
} tDeviceSockAddr;
I am using ffi.cdef() to define this structure. Running the unit test returns the (kind of expected) following error :
TypeError: field 'tDeviceSockAddr.DeviceAddr' has ctype 'struct sockaddr_in' of unknown size
My first thought was how do I load the whole netinet/in.h, but being new to CFFI, I am not sure that this is the way to go.
Is it possible to load netinet/in.h correctly? if so, how?
If not, what is the way to do this?
If you are using ffi.dlopen(), then you're out of luck. The only way to do that would be to declare explicitly the struct sockaddr_in in your cdef, maybe by copy-pasting bits of the Linux headers, assuming you're on Linux---and then of course the result is not portable.
You may want instead of look into using a proper ffibuilder approach, which require a compiler at installation time but lets you use any external include file. It's the mode described at https://cffi.readthedocs.io/en/latest/overview.html#main-mode-of-usage. In that mode you would write struct sockaddr_in { ...; }; in the cdef(), with literally dot-dot-dot, if you don't need the content of struct sockaddr_in from Python; or if you do you can include the fields that you need, but be sure to also write "...;", which means "this is a partial declaration; please use the real header to fix the order of fields and total size of the structure".