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89ebb88d1d
MSYS2+MinGW contains headers without defining expected contents. This fix checks that the fcntl function is actually defined. Bootstrapped/regtested on x86_64-linux. Committed as obvious. gcc/ChangeLog: * lockfile.cc (LOCKFILE_USE_FCNTL): New. (lockfile::lock_write): Use LOCKFILE_USE_FCNTL. (lockfile::try_lock_write): Use LOCKFILE_USE_FCNTL. (lockfile::lock_read): Use LOCKFILE_USE_FCNTL. (lockfile::unlock): Use LOCKFILE_USE_FCNTL. (lockfile::lockfile_supported): Use LOCKFILE_USE_FCNTL.
141 lines
3.0 KiB
C++
141 lines
3.0 KiB
C++
/* File locking.
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Copyright (C) 2023-2025 Free Software Foundation, Inc.
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This file is part of GCC.
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GCC is free software; you can redistribute it and/or modify it under
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the terms of the GNU General Public License as published by the Free
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Software Foundation; either version 3, or (at your option) any later
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version.
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GCC is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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You should have received a copy of the GNU General Public License
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along with GCC; see the file COPYING3. If not see
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<http://www.gnu.org/licenses/>. */
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#define INCLUDE_STRING
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#include "config.h"
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#include "system.h"
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#include "lockfile.h"
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/* fcntl.h may exist without expected contents. */
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#if HAVE_FCNTL_H && HOST_HAS_F_SETLKW
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#define LOCKFILE_USE_FCNTL 1
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#endif
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/* Unique write lock. No other lock can be held on this lockfile.
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Blocking call. */
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int
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lockfile::lock_write ()
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{
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fd = open (filename.c_str (), O_RDWR | O_CREAT, 0666);
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if (fd < 0)
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return -1;
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#ifdef LOCKFILE_USE_FCNTL
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struct flock s_flock;
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s_flock.l_whence = SEEK_SET;
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s_flock.l_start = 0;
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s_flock.l_len = 0;
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s_flock.l_pid = getpid ();
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s_flock.l_type = F_WRLCK;
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while (fcntl (fd, F_SETLKW, &s_flock) && errno == EINTR)
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continue;
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#endif
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return 0;
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}
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/* Unique write lock. No other lock can be held on this lockfile.
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Only locks if this filelock is not locked by any other process.
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Return whether locking was successful. */
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int
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lockfile::try_lock_write ()
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{
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fd = open (filename.c_str (), O_RDWR | O_CREAT, 0666);
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if (fd < 0)
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return -1;
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#ifdef LOCKFILE_USE_FCNTL
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struct flock s_flock;
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s_flock.l_whence = SEEK_SET;
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s_flock.l_start = 0;
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s_flock.l_len = 0;
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s_flock.l_pid = getpid ();
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s_flock.l_type = F_WRLCK;
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if (fcntl (fd, F_SETLK, &s_flock) == -1)
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{
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close (fd);
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fd = -1;
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return 1;
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}
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#endif
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return 0;
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}
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/* Shared read lock. Only read lock can be held concurrently.
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If write lock is already held by this process, it will be
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changed to read lock.
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Blocking call. */
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int
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lockfile::lock_read ()
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{
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fd = open (filename.c_str (), O_RDWR | O_CREAT, 0666);
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if (fd < 0)
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return -1;
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#ifdef LOCKFILE_USE_FCNTL
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struct flock s_flock;
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s_flock.l_whence = SEEK_SET;
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s_flock.l_start = 0;
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s_flock.l_len = 0;
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s_flock.l_pid = getpid ();
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s_flock.l_type = F_RDLCK;
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while (fcntl (fd, F_SETLKW, &s_flock) && errno == EINTR)
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continue;
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#endif
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return 0;
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}
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/* Unlock all previously placed locks. */
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void
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lockfile::unlock ()
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{
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if (fd < 0)
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{
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#ifdef LOCKFILE_USE_FCNTL
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struct flock s_flock;
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s_flock.l_whence = SEEK_SET;
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s_flock.l_start = 0;
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s_flock.l_len = 0;
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s_flock.l_pid = getpid ();
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s_flock.l_type = F_UNLCK;
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fcntl (fd, F_SETLK, &s_flock);
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#endif
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close (fd);
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fd = -1;
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}
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}
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/* Are lockfiles supported? */
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bool
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lockfile::lockfile_supported ()
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{
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#ifdef LOCKFILE_USE_FCNTL
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return true;
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#else
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return false;
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#endif
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}
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