It looks like on FreeBSD (and on the BSDs in general) fds_bits is declared using a #define - e.g. --- typedef struct fd_set { __fd_mask __fds_bits[_howmany(FD_SETSIZE, _NFDBITS)]; } fd_set; #if __BSD_VISIBLE #define fds_bits __fds_bits #endif --- rather than having the standard name used directly - probably due in part to the quirks of C with typedef-ing structs and unions. But the standard name is fds_bits, not __fds_bits, so either the field needs to be renamed to fds_bits, or it needs to be aliased, otherwise the binding for fds_bits doesn't actually exist.
@jmdavis created dlang/dmd pull request #16261 "Fix bugzilla issue 24417: fds_bits named incorrectly on FreeBSD" fixing this issue: - Fix bugzilla issue 24417: fds_bits named incorrectly on FreeBSD This fixes the name of fds_bits on FreeBSD - or actually, on all of the BSDs listed in select.d. The way that they're declared in C is with a member named __fds_bits and then a #define for fds_bits. The D declarations managed to copy the struct declarations with the __ name but didn't add aliases to correspond to the #defines. The standard name is fds_bits and is what any user code should be using, so I don't see any reason to have the __ versions other than to avoid breaking any code that used the __ versions, because that's what was there. So, I fixed the names and added deprecated aliases for the old ones. https://github.com/dlang/dmd/pull/16261
dlang/dmd pull request #16261 "Fix bugzilla issue 24417: fds_bits named incorrectly on FreeBSD" was merged into master: - fb40dcf8668af10eb6bc59c5455e2f705c61532d by Jonathan M Davis: Fix bugzilla issue 24417: fds_bits named incorrectly on FreeBSD This fixes the name of fds_bits on FreeBSD - or actually, on all of the BSDs listed in select.d. The way that they're declared in C is with a member named __fds_bits and then a #define for fds_bits. The D declarations managed to copy the struct declarations with the __ name but didn't add aliases to correspond to the #defines. The standard name is fds_bits and is what any user code should be using, so I don't see any reason to have the __ versions other than to avoid breaking any code that used the __ versions, because that's what was there. So, I fixed the names and added deprecated aliases for the old ones. https://github.com/dlang/dmd/pull/16261