• Simon McVittie's avatar
    build: Never use poll() on Darwin family (macOS, etc.) or Interix · 6cb51b22
    Simon McVittie authored
    Doing a runtime check in configure.ac (AC_RUN_IFELSE) has several
    disadvantages:
    
    * It doesn't work when cross-compiling. For example, if we build macOS
      binaries on a Linux system, we'd assume that poll() works, but in
      fact it won't.
    
    * It checks the build system capabilities, but that is not necessarily
      appropriate if (for example) a macOS 10.10 user builds binaries that
      could be used by macOS 10.12 or macOS 10.9 users.
    
    * It checks for one specific failure mode, but macOS seems to have a
      history of various implementation issues in poll().
    
    * If we want it to work in CMake, we have to duplicate it in the CMake
      build system.
    
    None of these is a showstopper on its own, but the combination of all
    of them makes the current approach to avoiding the broken poll() on
    macOS look unreliable. libcurl, a widely-portable library making
    extensive use of sockets, specifically doesn't use poll() on Darwin
    (macOS, iOS, etc.) or on Interix; let's follow their example here.
    
    See also https://bugzilla.gnome.org/show_bug.cgi?id=302672 and
    https://daniel.haxx.se/blog/2016/10/11/poll-on-mac-10-12-is-broken/
    for some relevant history.
    Signed-off-by: Simon McVittie's avatarSimon McVittie <smcv@collabora.com>
    Resolves: #232
    (cherry picked from commit 0414ea65)
    6cb51b22
configure.ac 61.8 KB