blob: 134f7ac25cc0525d1ce62756451b2c18b084d05a [file] [log] [blame]
// Copyright 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// When the default version of close used on Mac OS X fails with EINTR, the
// file descriptor is not in a deterministic state. It may have been closed,
// or it may not have been. This makes it impossible to gracefully recover
// from the error. If the close is retried after the FD has been closed, the
// subsequent close can report EBADF, or worse, it can close an unrelated FD
// opened by another thread. If the close is not retried after the FD has been
// left open, the FD is leaked. Neither of these are good options.
// Mac OS X provides an alternate version of close, close$NOCANCEL. This
// version will never fail with EINTR before the FD is actually closed. With
// this version, it is thus safe to call close without checking for EINTR (as
// the HANDLE_EINTR macro does) and not risk leaking the FD. In fact, mixing
// this verison of close with HANDLE_EINTR is hazardous.
// The $NOCANCEL variants of various system calls are activated by compiling
// with __DARWIN_NON_CANCELABLE, which prevents them from being pthread
// cancellation points. Rather than taking such a heavy-handed approach, this
// file implements an alternative: to use the $NOCANCEL variant of close (thus
// preventing it from being a pthread cancellation point) without affecting
// any other system calls.
// This file operates by providing a close function with the non-$NOCANCEL
// symbol name expected for the compilation environment as set by <unistd.h>
// and <sys/cdefs.h> (the DARWIN_ALIAS_C macro). That function calls the
// $NOCANCEL variant, which is resolved from libsyscall. By linking with this
// version of close prior to the libsyscall version, close's implementation is
// overridden.
#include <sys/cdefs.h>
// If the non-cancelable variants of all system calls have already been
// chosen, do nothing.
extern "C" {
// When there's a choice between UNIX2003 and pre-UNIX2003 and UNIX2003 has
// been chosen:
#define close_interface close$UNIX2003
#define close_implementation close$NOCANCEL$UNIX2003
// When there's a choice between UNIX2003 and pre-UNIX2003 and pre-UNIX2003
// has been chosen. There's no close$NOCANCEL symbol in this case, so use
// close$NOCANCEL$UNIX2003 as the implementation. It does the same thing
// that close$NOCANCEL would do.
#define close_interface close
#define close_implementation close$NOCANCEL$UNIX2003
// When only UNIX2003 is supported:
#define close_interface close
#define close_implementation close$NOCANCEL
int close_implementation(int fd);
int close_interface(int fd) {
return close_implementation(fd);
#undef close_interface
#undef close_implementation
} // extern "C"