wutsocket fixes: select() handles timeout wrong, and poll() lacks a safety check #428
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added 2 commits
October 6, 2025 11:52
- Move the nfds argument restriction to the nsysnet side. - Allow user-defined FD_SETSIZE, since newlib's fd_set allow custom sizes. - Define __socklen_t_defined when socklen_t is typedefed.
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The main issue fixed here is the incompatible implementation of
select()in nsysnet: for BSDselect(), on timeout (zero return value) it's supposed to clear thefd_setarguments. As far as I could test, nsysnetselect()leaves the arguments untouched on timeout; so the latter part of wutoscketselect()will simply add the sockets back to thefd_sets. An early return, after the arguments are zeroed, is enough to ensure the correct result.Also in
select(), the check againstFD_SETSIZEwas removed, as it's a pointless restriction. If the user exceededFD_SETSIZEin the arguments, we're already in undefined behavior territory, and the runtime stack was already overflown before even callingselect().The definition of
FD_SETSIZEis now conditional, allowing it to be a custom limit, as it was always intended. The definition offd_setin newlib is an array that usesFD_SETSIZE.Both
select()andpoll()received a check againstNSYSNET_FD_SETSIZE, to avoid callingNSYSNET_FD_SETwith an invalid fd. Even though it's just setting a bit in auint32_t(instead of writing to an array of incorrect size), bit-shifts larger than the type are undefined behavior.