@node fcntl.h
@section @file{fcntl.h}

POSIX specification:@* @url{https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/fcntl.h.html}

Gnulib module: fcntl-h

Portability problems fixed by Gnulib:
@itemize
@item
The type @code{pid_t} is not defined on some platforms:
MSVC 14.

@item
The type @code{mode_t} is not defined on some platforms:
MSVC 14.

@item
@samp{O_CLOEXEC}, @samp{O_DIRECTORY}, @samp{O_DSYNC}, @samp{O_NOCTTY},
@samp{O_NOFOLLOW}, @samp{O_RSYNC}, @samp{O_SYNC},
and @samp{O_TTY_INIT} are not defined on some platforms.  Gnulib defines
these macros to 0, which is generally safe.

@item
@samp{O_NONBLOCK} is not defined on some platforms.  If the
@samp{nonblocking} module is in use, gnulib guarantees a working
non-zero value; otherwise, the gnulib replacement is 0.

@item
@samp{O_EXEC} and @samp{O_SEARCH} are not defined on some platforms.
Gnulib defines these macros to @samp{O_RDONLY}, which is typically 0.
The @samp{O_PATH} macro of GNU/Linux is not a suitable substitute, as
fchmod fails with @samp{errno==EBADF} when invoked on a file
descriptor that was opened with @samp{O_PATH}.

@item
@samp{O_ACCMODE} is not defined on some platforms:
MSVC 14.

@item
The @samp{O_ACCMODE} mask mistakenly omits @samp{O_SEARCH} and
@samp{O_EXEC} on some platforms:
Cygwin.

@item
@samp{O_BINARY}, @samp{O_TEXT} (not specified by POSIX, but essential for
portability to native Windows platforms) are defined on some platforms but
not on others.

@item
@samp{O_CLOEXEC}, @samp{O_NOFOLLOW}, and @samp{O_TTY_INIT}
are defined to values that are too large for an @code{int} on some platforms:
AIX 7.1 with XL C 12.1.

@item
@samp{O_DIRECT}, @samp{O_IGNORE_CTTY}, @samp{O_NDELAY},
@samp{O_NOATIME}, @samp{O_NOLINK}, @samp{O_NOLINKS}, and
@samp{O_NOTRANS} (not specified by POSIX) are defined
on some platforms but not on others.

@item
@samp{FD_CLOEXEC}, @samp{F_DUPFD}, and @samp{F_GETFD} are not defined
on some platforms:
mingw, MSVC 14.

@item
@samp{F_DUPFD_CLOEXEC} is not defined on some platforms:
Mac OS X 10.5, FreeBSD 6.0, NetBSD 5.0, OpenBSD 3.8, AIX 5.1, HP-UX 11,
IRIX 6.5, Solaris 11 2010-11, Cygwin 1.7.1, mingw, MSVC 14.

@item
@samp{AT_FDCWD}, @samp{AT_EACCESS}, @samp{AT_SYMLINK_NOFOLLOW},
@samp{AT_SYMLINK_FOLLOW}, and @samp{AT_REMOVEDIR}
are not defined on many platforms:
glibc 2.3.6, Mac OS X 10.5, FreeBSD 6.0, NetBSD 5.0, OpenBSD 3.8, AIX 5.1, HP-UX 11, IRIX 6.5, Cygwin 1.5.x, mingw, MSVC 14.

@item
@samp{AT_FDCWD} is defined with a value too large for an @code{int} on some
platforms:
Solaris 11.3.
@end itemize

Portability problems not fixed by Gnulib:
@itemize
@item
@samp{F_SETFD}, @samp{F_GETFL}, @samp{F_SETFL}, @samp{F_GETLK},
@samp{F_SETLK}, @samp{F_SETLKW}, @samp{F_GETOWN}, and @samp{F_SETOWN}
are not defined on some platforms:
mingw, MSVC 14.

@item
@samp{POSIX_FADV_DONTNEED}, @samp{POSIX_FADV_NOREUSE},
@samp{POSIX_FADV_NORMAL}, @samp{POSIX_FADV_RANDOM},
@samp{POSIX_FADV_SEQUENTIAL}, and @samp{POSIX_FADV_WILLNEED} are not
defined on some platforms.
@end itemize
