kc3-lang/gnulib/doc/posix-functions/select.texi

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• Hash : 9500a55f
  Author :
  Date : 2012-10-02T15:29:13
  

  select: reject invalid file descriptors
  
  POSIX requires invalid file descriptors to be detected rather than
  silently ignored.  FreeBSD 8.2 detects if fd 0 has been closed
  and appears in a set while fd 1 is still open, but mistakenly
  optimizes and refuses to check any fds in the set beyond the
  maximum open fd.
  
  * m4/select.m4 (gl_FUNC_SELECT): Probe for FreeBSD bug.
  * lib/select.c (rpl_select) [!win32]: Work around it.
  * modules/select (Depends-on): Add dup2.
  * doc/posix-functions/select.texi (select): Document this.
  

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• doc/posix-functions/select.texi

• @node select
  @section @code{select}
  @findex select
  
  POSIX specification:@* @url{http://www.opengroup.org/onlinepubs/9699919799/functions/select.html}
  
  Gnulib module: select
  
  Portability problems fixed by Gnulib:
  @itemize
  @item
  On Windows platforms (excluding Cygwin), @code{select} can only be
  called on descriptors created by the @code{socket} function, not on regular
  file descriptors.
  @item
  On Windows platforms (excluding Cygwin), error codes for @code{accept} are not
  placed in @code{errno}, and @code{WSAGetLastError} must be used instead.
  @item
  This function fails when the @code{nfds} argument is 0 on some platforms:
  Interix 3.5.
  @item
  On some platforms, this function fails to detect invalid fds with
  EBADF, but only if they lie beyond the current maximum open fd:
  FreeBSD 8.2.
  @end itemize
  
  Portability problems not fixed by Gnulib:
  @itemize
  @item
  When you call @code{select} with a timeout, some implementations modify the
  timeout parameter so that upon return from the function, it contains the
  amount of time not slept.  Other implementations leave the timeout parameter
  unmodified.
  @item
  On BeOS, @code{select} can only be called on descriptors created by the
  @code{socket} function, not on regular file descriptors.
  @item
  Under Windows, when passing a pipe, Gnulib's @code{select} replacement might
  return 0 even before the timeout has passed.  Programs using it with pipes can
  thus busy wait.
  @item
  On Solaris 2.6 and older, @code{select} applied to a file descriptor opened
  for reading and associated with @code{/dev/null} hangs, waiting for input,
  when instead it should return immediately.
  @item
  On Linux, when some file descriptor refers to a regular file, @code{select}
  may fail, setting @code{errno} to @code{EBADF}.
  @item
  This function is declared in @code{<unistd.h>}, not @code{<sys/select.h>},
  on some platforms:
  IRIX 5.3.
  @end itemize
  

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