CFFI_EXCLUDE for KMC Compilation

[dccutrig]

Email from Hayk, capturing here to test results:

When doing a KMC build with PR #210 we ran into some problems with the CFFI code on the KMC side. Specifically with this line: https://github.jpl.nasa.gov/ASEC/AMMOS-CryptoLib/blob/master/kmc_sdls/kmc_sdls_python/_cffi_src/tasks.py#L29

If you don’t have access to the KMC repo it’s the output produced by the following GCC pre-processing line that CFFI can’t parse.
gcc -E -Ikmc_sdls/public_inc -I/usr/local/include -I../../../CryptoLib/include ../../public_inc/kmc_sdls.h

The root cause turned out to be with these 2 lines in crypto_structs.h
#include <stdio.h>
#include <stdlib.h>
https://github.com/nasa/CryptoLib/pull/210/files#diff-ff3b1a31169cc448e7dce70a6b076fdffe88b286df835bfdfeec10405dafde45R28
https://github.com/nasa/CryptoLib/pull/210/files#diff-ff3b1a31169cc448e7dce70a6b076fdffe88b286df835bfdfeec10405dafde45R29

When standard C libraries are included in the gcc -E (preprocessing) step, it includes the standard library contents in the pre processed output which the Python CFFI parsing code can’t handle.

One possible solution to this is to update the following block of code in https://github.com/nasa/CryptoLib/blob/dev/include/crypto_structs.h#L24 :
FROM:

#ifdef NOS3 // NOS3/cFS build is ready
#include "common_types.h"
#else // Assume build outside of NOS3/cFS infrastructure
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#endif

TO:

#ifdef NOS3 // NOS3/cFS build is ready
#include "common_types.h"
#else // Assume build outside of NOS3/cFS infrastructure
#include <stdint.h>
#ifndef CFFI_EXCLUDE // Exclude libraries that CFFI parser can’t process
#include <stdio.h>
#include <stdlib.h>
#endif
#endif

With the above update we can then run the GCC command with -D CFFI_EXCLUDE to exclude the standard libraries
gcc -E -D CFFI_EXCLUDE -Ikmc_sdls/public_inc -I/usr/local/include -I../../../CryptoLib/include ../../public_inc/kmc_sdls.h

[jlucas9]

Merged to dev