Checking other libcs (note that "edit the header" is not that difficult to automate): bionic - must edit the header dietlibc - must edit the header glibc

Checking other libcs (note that "edit the header" is not that difficult to automate): bionic - must edit the header dietlibc - must edit the header glibc - undocumented but reliable, see the dance in the original post klibc - must edit <linux/posix_types.h> (which, note, sabotages glibc) MUSL - must edit the header newlib - documented in header, just `#define FD_SETSIZE` before you `#include <sys/select.h>` uclibc - as glibc (since it's a distant fork). Note that `poll.c` for old uclinux kernels is implemented in terms of `select` with dynamic `fd_set` sizing logic! freebsd - properly documented, just `#define FD_SETSIZE` first netbsd - properly documented, just `#define FD_SETSIZE` first openbsd - documented just in the header now (formerly in the man page too), just `#define FD_SETSIZE` first solaris - properly documented, just `#define FD_SETSIZE` first macos - properly documented, just `#define FD_SETSIZE` first winsock - properly documented, just `#define FD_SETSIZE` first, but note the API is not actually the same