Use unique logfile names when starting server with -displayfd

nx-X11/programs/Xserver/include/os.h

@@ -520,6 +520,7 @@ typedef enum {
 #endif
 
 extern const char *LogInit(const char *fname, const char *backup);
+extern void LogSetDisplay(void);
 extern void LogClose(void);
 extern Bool LogSetParameter(LogParameter param, int value);
 extern void LogVWrite(int verb, const char *f, va_list args);

nx-X11/programs/Xserver/os/connection.c

@@ -434,6 +434,7 @@ CreateWellKnownSockets(void)
 	    FatalError("Failed to find a socket to listen on");
 	snprintf(dynamic_display, sizeof(dynamic_display), "%d", i);
 	display = dynamic_display;
+	LogSetDisplay();
     }
 
     ListenTransFds = malloc(ListenTransCount * sizeof (int));

nx-X11/programs/Xserver/os/log.c

@@ -179,48 +179,87 @@ static Bool needBuffer = TRUE;
 #endif
 
 /*
+ * LogFilePrep is called to setup files for logging, including getting
+ * an old file out of the way, but it doesn't actually open the file,
+ * since it may be used for renaming a file we're already logging to.
+ */
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wformat-nonliteral"
+
+static char *
+LogFilePrep(const char *fname, const char *backup, const char *idstring)
+{
+    char *logFileName = NULL;
+
+    if (asprintf(&logFileName, fname, idstring) == -1)
+	FatalError("Cannot allocate space for the log file name\n");
+
+    if (backup && *backup) {
+	struct stat buf;
+
+    if (!stat(logFileName, &buf) && S_ISREG(buf.st_mode)) {
+	    char *suffix;
+	    char *oldLog;
+
+	    if ((asprintf(&suffix, backup, idstring) == -1) ||
+		(asprintf(&oldLog, "%s%s", logFileName, suffix) == -1)) {
+		FatalError("Cannot allocate space for the log file name\n");
+	    }
+	    free(suffix);
+
+	    if (rename(logFileName, oldLog) == -1) {
+		FatalError("Cannot move old log file \"%s\" to \"%s\"\n",
+			   logFileName, oldLog);
+	    }
+	    free(oldLog);
+	}
+    }
+    else {
+	if (remove(logFileName) != 0) {
+	    FatalError("Cannot remove old log file \"%s\": %s\n",
+		       logFileName, strerror(errno));
+	}
+    }
+
+    return logFileName;
+}
+#pragma GCC diagnostic pop
+
+/*
  * LogInit is called to start logging to a file.  It is also called (with
  * NULL arguments) when logging to a file is not wanted.  It must always be
  * called, otherwise log messages will continue to accumulate in a buffer.
  *
  * %s, if present in the fname or backup strings, is expanded to the display
- * string.
+ * string (or to a string containing the pid if the display is not yet set).
  */
 
+static char *saved_log_fname;
+static char *saved_log_backup;
+static char *saved_log_tempname;
+
 const char *
 LogInit(const char *fname, const char *backup)
 {
     char *logFileName = NULL;
 
     if (fname && *fname) {
-	/* malloc() can't be used yet. */
-	logFileName = malloc(strlen(fname) + strlen(display) + 1);
-	if (!logFileName)
-	    FatalError("Cannot allocate space for the log file name\n");
-	sprintf(logFileName, fname, display);
-
-	if (backup && *backup) {
-	    struct stat buf;
-
-	    if (!stat(logFileName, &buf) && S_ISREG(buf.st_mode)) {
-		char *suffix;
-		char *oldLog;
-
-		oldLog = malloc(strlen(logFileName) + strlen(backup) +
-				strlen(display) + 1);
-		suffix = malloc(strlen(backup) + strlen(display) + 1);
-		if (!oldLog || !suffix)
-		    FatalError("Cannot allocate space for the log file name\n");
-		sprintf(suffix, backup, display);
-		sprintf(oldLog, "%s%s", logFileName, suffix);
-		free(suffix);
-		if (rename(logFileName, oldLog) == -1) {
-		    FatalError("Cannot move old log file (\"%s\" to \"%s\"\n",
-			       logFileName, oldLog);
-		}
-		free(oldLog);
-	    }
-	}
+	if (displayfd != -1) {
+	    /* Display isn't set yet, so we can't use it in filenames yet. */
+	    char pidstring[32];
+	    snprintf(pidstring, sizeof(pidstring), "pid-%ld",
+		     (unsigned long) getpid());
+	    logFileName = LogFilePrep(fname, backup, pidstring);
+	    saved_log_tempname = logFileName;
+
+	    /* Save the patterns for use when the display is named. */
+	    saved_log_fname = strdup(fname);
+	    if (backup == NULL)
+		saved_log_backup = NULL;
+	    else
+		saved_log_backup = strdup(backup);
+	} else
+	    logFileName = LogFilePrep(fname, backup, display);
 	if ((logFile = fopen(logFileName, "w")) == NULL)
 	    FatalError("Cannot open log file \"%s\"\n", logFileName);
 	setvbuf(logFile, NULL, _IONBF, 0);
@@ -250,6 +289,36 @@ LogInit(const char *fname, const char *backup)
 }
 
 void
+LogSetDisplay(void)
+{
+    if (saved_log_fname) {
+	char *logFileName;
+
+	logFileName = LogFilePrep(saved_log_fname, saved_log_backup, display);
+
+	if (rename(saved_log_tempname, logFileName) == 0) {
+	    LogMessageVerb(X_PROBED, 0,
+			   "Log file renamed from \"%s\" to \"%s\"\n",
+			   saved_log_tempname, logFileName);
+
+	    if (strlen(saved_log_tempname) >= strlen(logFileName))
+		strncpy(saved_log_tempname, logFileName,
+			strlen(saved_log_tempname));
+	}
+	else {
+	    ErrorF("Failed to rename log file \"%s\" to \"%s\": %s\n",
+		   saved_log_tempname, logFileName, strerror(errno));
+	}
+
+	/* free newly allocated string - can't free old one since existing
+	   pointers to it may exist in DDX callers. */
+	free(logFileName);
+	free(saved_log_fname);
+	free(saved_log_backup);
+    }
+}
+
+void
 LogClose()
 {
     if (logFile) {