--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/rust/chg/src/sighandlers.c Mon Sep 24 22:04:57 2018 +0900
@@ -0,0 +1,177 @@
+/*
+ * Signal handlers for cHg
+ *
+ * Copyright 2011, 2018 Yuya Nishihara <yuya@tcha.org>
+ *
+ * This software may be used and distributed according to the terms of the
+ * GNU General Public License version 2 or any later version.
+ */
+
+#include <assert.h>
+#include <errno.h>
+#include <signal.h>
+#include <string.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#ifdef __GNUC__
+#define UNUSED_ __attribute__((unused))
+#else
+#define UNUSED_
+#endif
+
+static pid_t pagerpid = 0;
+static pid_t peerpgid = 0;
+static pid_t peerpid = 0;
+
+static void forwardsignal(int sig)
+{
+ assert(peerpid > 0);
+ (void)kill(peerpid, sig);
+}
+
+static void forwardsignaltogroup(int sig)
+{
+ /* prefer kill(-pgid, sig), fallback to pid if pgid is invalid */
+ pid_t killpid = peerpgid > 1 ? -peerpgid : peerpid;
+ (void)kill(killpid, sig);
+}
+
+static void handlestopsignal(int sig)
+{
+ sigset_t unblockset, oldset;
+ struct sigaction sa, oldsa;
+ if (sigemptyset(&unblockset) < 0)
+ return;
+ if (sigaddset(&unblockset, sig) < 0)
+ return;
+ memset(&sa, 0, sizeof(sa));
+ sa.sa_handler = SIG_DFL;
+ sa.sa_flags = SA_RESTART;
+ if (sigemptyset(&sa.sa_mask) < 0)
+ return;
+
+ forwardsignal(sig);
+ if (raise(sig) < 0) /* resend to self */
+ return;
+ if (sigaction(sig, &sa, &oldsa) < 0)
+ return;
+ if (sigprocmask(SIG_UNBLOCK, &unblockset, &oldset) < 0)
+ return;
+ /* resent signal will be handled before sigprocmask() returns */
+ if (sigprocmask(SIG_SETMASK, &oldset, NULL) < 0)
+ return;
+ if (sigaction(sig, &oldsa, NULL) < 0)
+ return;
+}
+
+static void handlechildsignal(int sig UNUSED_)
+{
+ if (peerpid == 0 || pagerpid == 0)
+ return;
+ /* if pager exits, notify the server with SIGPIPE immediately.
+ * otherwise the server won't get SIGPIPE if it does not write
+ * anything. (issue5278) */
+ if (waitpid(pagerpid, NULL, WNOHANG) == pagerpid)
+ kill(peerpid, SIGPIPE);
+}
+
+/*
+ * Installs signal handlers.
+ *
+ * Returns 0 on success, -1 on error and errno is set appropriately.
+ * Installed handlers wouldn't be cleaned up on error.
+ */
+int setupsignalhandler(pid_t pid, pid_t pgid)
+{
+ if (pid <= 0) {
+ errno = EINVAL;
+ return -1;
+ }
+ peerpid = pid;
+ peerpgid = (pgid <= 1 ? 0 : pgid);
+
+ struct sigaction sa;
+ memset(&sa, 0, sizeof(sa));
+
+ /* deadly signals meant to be sent to a process group:
+ * - SIGHUP: usually generated by the kernel, when termination of a
+ * process causes that process group to become orphaned
+ * - SIGINT: usually generated by the terminal */
+ sa.sa_handler = forwardsignaltogroup;
+ sa.sa_flags = SA_RESTART;
+ if (sigemptyset(&sa.sa_mask) < 0)
+ return -1;
+ if (sigaction(SIGHUP, &sa, NULL) < 0)
+ return -1;
+ if (sigaction(SIGINT, &sa, NULL) < 0)
+ return -1;
+
+ /* terminate frontend by double SIGTERM in case of server freeze */
+ sa.sa_handler = forwardsignal;
+ sa.sa_flags |= SA_RESETHAND;
+ if (sigaction(SIGTERM, &sa, NULL) < 0)
+ return -1;
+
+ /* notify the worker about window resize events */
+ sa.sa_flags = SA_RESTART;
+ if (sigaction(SIGWINCH, &sa, NULL) < 0)
+ return -1;
+ /* forward user-defined signals */
+ if (sigaction(SIGUSR1, &sa, NULL) < 0)
+ return -1;
+ if (sigaction(SIGUSR2, &sa, NULL) < 0)
+ return -1;
+ /* propagate job control requests to worker */
+ sa.sa_handler = forwardsignal;
+ sa.sa_flags = SA_RESTART;
+ if (sigaction(SIGCONT, &sa, NULL) < 0)
+ return -1;
+ sa.sa_handler = handlestopsignal;
+ sa.sa_flags = SA_RESTART;
+ if (sigaction(SIGTSTP, &sa, NULL) < 0)
+ return -1;
+ /* get notified when pager exits */
+ sa.sa_handler = handlechildsignal;
+ sa.sa_flags = SA_RESTART;
+ if (sigaction(SIGCHLD, &sa, NULL) < 0)
+ return -1;
+
+ return 0;
+}
+
+/*
+ * Restores signal handlers to the default, and masks SIGINT.
+ *
+ * Returns 0 on success, -1 on error and errno is set appropriately.
+ */
+int restoresignalhandler(void)
+{
+ struct sigaction sa;
+ memset(&sa, 0, sizeof(sa));
+ sa.sa_handler = SIG_DFL;
+ sa.sa_flags = SA_RESTART;
+ if (sigemptyset(&sa.sa_mask) < 0)
+ return -1;
+
+ if (sigaction(SIGHUP, &sa, NULL) < 0)
+ return -1;
+ if (sigaction(SIGTERM, &sa, NULL) < 0)
+ return -1;
+ if (sigaction(SIGWINCH, &sa, NULL) < 0)
+ return -1;
+ if (sigaction(SIGCONT, &sa, NULL) < 0)
+ return -1;
+ if (sigaction(SIGTSTP, &sa, NULL) < 0)
+ return -1;
+ if (sigaction(SIGCHLD, &sa, NULL) < 0)
+ return -1;
+
+ /* ignore Ctrl+C while shutting down to make pager exits cleanly */
+ sa.sa_handler = SIG_IGN;
+ if (sigaction(SIGINT, &sa, NULL) < 0)
+ return -1;
+
+ peerpid = 0;
+ return 0;
+}