Add an unpatched version of xz, XZ Utils, to /trunk/deps/third_party

xz/src/xz/signals.c

+///////////////////////////////////////////////////////////////////////////////
+//
+/// \file       signals.c
+/// \brief      Handling signals to abort operation
+//
+//  Author:     Lasse Collin
+//
+//  This file has been put into the public domain.
+//  You can do whatever you want with this file.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#include "private.h"
+
+
+volatile sig_atomic_t user_abort = false;
+
+
+#if !(defined(_WIN32) && !defined(__CYGWIN__))
+
+/// If we were interrupted by a signal, we store the signal number so that
+/// we can raise that signal to kill the program when all cleanups have
+/// been done.
+static volatile sig_atomic_t exit_signal = 0;
+
+/// Mask of signals for which have have established a signal handler to set
+/// user_abort to true.
+static sigset_t hooked_signals;
+
+/// True once signals_init() has finished. This is used to skip blocking
+/// signals (with uninitialized hooked_signals) if signals_block() and
+/// signals_unblock() are called before signals_init() has been called.
+static bool signals_are_initialized = false;
+
+/// signals_block() and signals_unblock() can be called recursively.
+static size_t signals_block_count = 0;
+
+
+static void
+signal_handler(int sig)
+{
+        exit_signal = sig;
+        user_abort = true;
+        return;
+}
+
+
+extern void
+signals_init(void)
+{
+        // List of signals for which we establish the signal handler.
+        static const int sigs[] = {
+                SIGINT,
+                SIGTERM,
+#ifdef SIGHUP
+                SIGHUP,
+#endif
+#ifdef SIGPIPE
+                SIGPIPE,
+#endif
+#ifdef SIGXCPU
+                SIGXCPU,
+#endif
+#ifdef SIGXFSZ
+                SIGXFSZ,
+#endif
+        };
+
+        // Mask of the signals for which we have established a signal handler.
+        sigemptyset(&hooked_signals);
+        for (size_t i = 0; i < ARRAY_SIZE(sigs); ++i)
+                sigaddset(&hooked_signals, sigs[i]);
+
+        struct sigaction sa;
+
+        // All the signals that we handle we also blocked while the signal
+        // handler runs.
+        sa.sa_mask = hooked_signals;
+
+        // Don't set SA_RESTART, because we want EINTR so that we can check
+        // for user_abort and cleanup before exiting. We block the signals
+        // for which we have established a handler when we don't want EINTR.
+        sa.sa_flags = 0;
+        sa.sa_handler = &signal_handler;
+
+        for (size_t i = 0; i < ARRAY_SIZE(sigs); ++i) {
+                // If the parent process has left some signals ignored,
+                // we don't unignore them.
+                struct sigaction old;
+                if (sigaction(sigs[i], NULL, &old) == 0
+                                && old.sa_handler == SIG_IGN)
+                        continue;
+
+                // Establish the signal handler.
+                if (sigaction(sigs[i], &sa, NULL))
+                        message_signal_handler();
+        }
+
+        signals_are_initialized = true;
+
+        return;
+}
+
+
+#ifndef __VMS
+extern void
+signals_block(void)
+{
+        if (signals_are_initialized) {
+                if (signals_block_count++ == 0) {
+                        const int saved_errno = errno;
+                        mythread_sigmask(SIG_BLOCK, &hooked_signals, NULL);
+                        errno = saved_errno;
+                }
+        }
+
+        return;
+}
+
+
+extern void
+signals_unblock(void)
+{
+        if (signals_are_initialized) {
+                assert(signals_block_count > 0);
+
+                if (--signals_block_count == 0) {
+                        const int saved_errno = errno;
+                        mythread_sigmask(SIG_UNBLOCK, &hooked_signals, NULL);
+                        errno = saved_errno;
+                }
+        }
+
+        return;
+}
+#endif
+
+
+extern void
+signals_exit(void)
+{
+        const int sig = exit_signal;
+
+        if (sig != 0) {
+                struct sigaction sa;
+                sa.sa_handler = SIG_DFL;
+                sigfillset(&sa.sa_mask);
+                sa.sa_flags = 0;
+                sigaction(sig, &sa, NULL);
+                raise(exit_signal);
+        }
+
+        return;
+}
+
+#else
+
+// While Windows has some very basic signal handling functions as required
+// by C89, they are not really used, and e.g. SIGINT doesn't work exactly
+// the way it does on POSIX (Windows creates a new thread for the signal
+// handler). Instead, we use SetConsoleCtrlHandler() to catch user
+// pressing C-c, because that seems to be the recommended way to do it.
+//
+// NOTE: This doesn't work under MSYS. Trying with SIGINT doesn't work
+// either even if it appeared to work at first. So test using Windows
+// console window.
+
+static BOOL WINAPI
+signal_handler(DWORD type lzma_attribute((unused)))
+{
+        // Since we don't get a signal number which we could raise() at
+        // signals_exit() like on POSIX, just set the exit status to
+        // indicate an error, so that we cannot return with zero exit status.
+        set_exit_status(E_ERROR);
+        user_abort = true;
+        return TRUE;
+}
+
+
+extern void
+signals_init(void)
+{
+        if (!SetConsoleCtrlHandler(&signal_handler, TRUE))
+                message_signal_handler();
+
+        return;
+}
+
+#endif