if (__i == ((fd_set FAR *)(set))->fd_count) { \
if (((fd_set FAR *)(set))->fd_count < FD_SETSIZE) { \
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
((fd_set FAR *)(set))->fd_array[__i] = (fd); \
((fd_set FAR *)(set))->fd_count++; \
} \
} \
} while(0)
So if you attempted to put FD_SETSIZE + 1 sockets into an fd_set, it would just fail.
This effectively limits select to a maximum of FD_SETSIZE descriptors on Windows. I don't think that this limitiation exists on other platforms.
Correctly written programs dynamically allocate their FD_SETs to avoid these problems (or they use poll or some other mechanism instead).
-d
