| // 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. |
| |
| // http://crbug.com/269623 |
| // http://openradar.appspot.com/14999594 |
| // |
| // 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 |
| // $NOCANCEL variant, which is resolved from libsyscall. By linking with this |
| // version of close prior to the libsyscall version, close's implementation is |
| // overridden. |
| |
| #include <sys/cdefs.h> |
| |
| // If the non-cancelable variants of all system calls have already been |
| // chosen, do nothing. |
| #if !__DARWIN_NON_CANCELABLE |
| |
| extern "C" { |
| |
| #if __DARWIN_UNIX03 && !__DARWIN_ONLY_UNIX_CONFORMANCE |
| |
| // When there's a choice between UNIX2003 and pre-UNIX2003 and UNIX2003 has |
| // been chosen: |
| #define close_interface close$UNIX2003 |
| #define close_implementation close$NOCANCEL$UNIX2003 |
| |
| #elif !__DARWIN_UNIX03 && !__DARWIN_ONLY_UNIX_CONFORMANCE |
| |
| // 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 |
| |
| #else // __DARWIN_ONLY_UNIX_CONFORMANCE |
| |
| // When only UNIX2003 is supported: |
| #define close_interface close |
| #define close_implementation close$NOCANCEL |
| |
| #endif |
| |
| int close_implementation(int fd); |
| |
| int close_interface(int fd) { |
| return close_implementation(fd); |
| } |
| |
| #undef close_interface |
| #undef close_implementation |
| |
| } // extern "C" |
| |
| #endif // !__DARWIN_NON_CANCELABLE |