Using select(2) the right way

Re:Using select(2) the right way by adynatos on Monday June 05, 2017 @05:08AM (#14486210)

  unsigned long *wfds = (unsigned long *)wfds_out;

Unless fd_set has the same or stricter alignment requirements as unsigned long, and fd_set and unsigned long are compatible effective types, this line of code provokes undefined behaviour twice (breaks strict alignment and breaks effective type access).

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Re:Using select(2) the right way by beeforpork on Monday June 05, 2017 @05:40AM (#14486316)

In this case, it is most probably OK, because wfds_out comes from calloc(), which uses the largest possible alignment to work for any type (it returns void* and cannot know which types are inside the allocated memory, so it needs to assume the max on the architecture).

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