Simple differences - missing types and defines

Types, such as int32_t, socklen_t, etc.

Preprocessor symbols, e.g. IPTOS_THROUGHPUT, STDIN_FILENO

Solution:
Provide your own replacements

Be careful when defining things like PATH_MAX
You can introduce buffer overflows if you get it wrong
If you need to set it, then you have to provide functions that honour your limits

