+static FILE *errorfile;
+char *errorfilename;
+
+/* SHM logging variables */
+
+/* The name for the SHM (/i3-log-%pid). Will end up on /dev/shm on most
+ * systems. Global so that we can clean up at exit. */
+char *shmlogname = "";
+/* Size limit for the SHM log, by default 25 MiB. Can be overwritten using the
+ * flag --shmlog-size. */
+int shmlog_size = 0;
+/* If enabled, logbuffer will point to a memory mapping of the i3 SHM log. */
+static char *logbuffer;
+/* A pointer (within logbuffer) where data will be written to next. */
+static char *logwalk;
+/* A pointer to the shmlog header */
+static i3_shmlog_header *header;
+/* A pointer to the byte where we last wrapped. Necessary to not print the
+ * left-overs at the end of the ringbuffer. */
+static char *loglastwrap;
+/* Size (in bytes) of the i3 SHM log. */
+static int logbuffer_size;
+/* File descriptor for shm_open. */
+static int logbuffer_shm;
+
+/*
+ * Writes the offsets for the next write and for the last wrap to the
+ * shmlog_header.
+ * Necessary to print the i3 SHM log in the correct order.
+ *
+ */
+static void store_log_markers(void) {
+ header->offset_next_write = (logwalk - logbuffer);
+ header->offset_last_wrap = (loglastwrap - logbuffer);
+ header->size = logbuffer_size;
+}
+
+/*
+ * Initializes logging by creating an error logfile in /tmp (or
+ * XDG_RUNTIME_DIR, see get_process_filename()).
+ *
+ * Will be called twice if --shmlog-size is specified.
+ *
+ */
+void init_logging(void) {
+ if (!errorfilename) {
+ if (!(errorfilename = get_process_filename("errorlog")))
+ ELOG("Could not initialize errorlog\n");
+ else {
+ errorfile = fopen(errorfilename, "w");
+ if (fcntl(fileno(errorfile), F_SETFD, FD_CLOEXEC)) {
+ ELOG("Could not set close-on-exec flag\n");
+ }
+ }
+ }
+
+ /* If this is a debug build (not a release version), we will enable SHM
+ * logging by default, unless the user turned it off explicitly. */
+ if (logbuffer == NULL && shmlog_size > 0) {
+ /* Reserve 1% of the RAM for the logfile, but at max 25 MiB.
+ * For 512 MiB of RAM this will lead to a 5 MiB log buffer.
+ * At the moment (2011-12-10), no testcase leads to an i3 log
+ * of more than ~ 600 KiB. */
+ long long physical_mem_bytes;
+#if defined(__APPLE__)
+ int mib[2] = { CTL_HW, HW_MEMSIZE };
+ size_t length = sizeof(long long);
+ sysctl(mib, 2, &physical_mem_bytes, &length, NULL, 0);
+#else
+ physical_mem_bytes = (long long)sysconf(_SC_PHYS_PAGES) *
+ sysconf(_SC_PAGESIZE);
+#endif
+ logbuffer_size = min(physical_mem_bytes * 0.01, shmlog_size);
+ sasprintf(&shmlogname, "/i3-log-%d", getpid());
+ logbuffer_shm = shm_open(shmlogname, O_RDWR | O_CREAT | O_TRUNC, S_IREAD | S_IWRITE);
+ if (logbuffer_shm == -1) {
+ ELOG("Could not shm_open SHM segment for the i3 log: %s\n", strerror(errno));
+ return;
+ }
+
+ if (ftruncate(logbuffer_shm, logbuffer_size) == -1) {
+ close(logbuffer_shm);
+ shm_unlink("/i3-log-");
+ ELOG("Could not ftruncate SHM segment for the i3 log: %s\n", strerror(errno));
+ return;
+ }
+
+ logbuffer = mmap(NULL, logbuffer_size, PROT_READ | PROT_WRITE, MAP_SHARED, logbuffer_shm, 0);
+ if (logbuffer == MAP_FAILED) {
+ close(logbuffer_shm);
+ shm_unlink("/i3-log-");
+ ELOG("Could not mmap SHM segment for the i3 log: %s\n", strerror(errno));
+ logbuffer = NULL;
+ return;
+ }
+
+ /* Initialize with 0-bytes, just to be sure… */
+ memset(logbuffer, '\0', logbuffer_size);
+
+ header = (i3_shmlog_header*)logbuffer;
+
+ pthread_condattr_t cond_attr;
+ pthread_condattr_init(&cond_attr);
+ if (pthread_condattr_setpshared(&cond_attr, PTHREAD_PROCESS_SHARED) != 0)
+ ELOG("pthread_condattr_setpshared() failed, i3-dump-log -f will not work!\n");
+ pthread_cond_init(&(header->condvar), &cond_attr);
+
+ logwalk = logbuffer + sizeof(i3_shmlog_header);
+ loglastwrap = logbuffer + logbuffer_size;
+ store_log_markers();
+ }
+ atexit(purge_zerobyte_logfile);
+}