patch 8.0.0492: a failing client-server request can make Vim hang

Problem:    A failing client-server request can make Vim hang.
Solution:   Add a timeout argument to functions that wait.

Author: brammool

runtime/doc/eval.txt

@@ -6320,15 +6320,17 @@ reltimestr({time})				*reltimestr()*
 		{only available when compiled with the |+reltime| feature}
 
 							*remote_expr()* *E449*
-remote_expr({server}, {string} [, {idvar}])
+remote_expr({server}, {string} [, {idvar} [, {timeout}]])
 		Send the {string} to {server}.  The string is sent as an
 		expression and the result is returned after evaluation.
 		The result must be a String or a |List|.  A |List| is turned
 		into a String by joining the items with a line break in
 		between (not at the end), like with join(expr, "\n").
-		If {idvar} is present, it is taken as the name of a
-		variable and a {serverid} for later use with
+		If {idvar} is present and not empty, it is taken as the name
+		of a variable and a {serverid} for later use with
 		remote_read() is stored there.
+		If {timeout} is given the read times out after this many
+		seconds.  Otherwise a timeout of 600 seconds is used.
 		See also |clientserver| |RemoteReply|.
 		This function is not available in the |sandbox|.
 		{only available when compiled with the |+clientserver| feature}
@@ -6367,9 +6369,10 @@ remote_peek({serverid} [, {retvar}])		*remote_peek()*
 			:let repl = ""
 			:echo "PEEK: ".remote_peek(id, "repl").": ".repl
 
-remote_read({serverid})				*remote_read()*
+remote_read({serverid}, [{timeout}])			*remote_read()*
 		Return the oldest available reply from {serverid} and consume
-		it.  It blocks until a reply is available.
+		it.  Unless a {timeout} in seconds is given, it blocks until a
+		reply is available.
 		See also |clientserver|.
 		This function is not available in the |sandbox|.
 		{only available when compiled with the |+clientserver| feature}

src/evalfunc.c

@@ -739,10 +739,10 @@ static struct fst
     {"reltimefloat",	1, 1, f_reltimefloat},
 #endif
     {"reltimestr",	1, 1, f_reltimestr},
-    {"remote_expr",	2, 3, f_remote_expr},
+    {"remote_expr",	2, 4, f_remote_expr},
     {"remote_foreground", 1, 1, f_remote_foreground},
     {"remote_peek",	1, 2, f_remote_peek},
-    {"remote_read",	1, 1, f_remote_read},
+    {"remote_read",	1, 2, f_remote_read},
     {"remote_send",	2, 3, f_remote_send},
     {"remote_startserver", 1, 1, f_remote_startserver},
     {"remove",		2, 3, f_remove},
@@ -8515,6 +8515,7 @@ remote_common(typval_T *argvars, typval_T *rettv, int expr)
     char_u	*keys;
     char_u	*r = NULL;
     char_u	buf[NUMBUFLEN];
+    int		timeout = 0;
 # ifdef WIN32
     HWND	w;
 # else
@@ -8528,16 +8529,19 @@ remote_common(typval_T *argvars, typval_T *rettv, int expr)
     if (check_connection() == FAIL)
 	return;
 # endif
+    if (argvars[2].v_type != VAR_UNKNOWN
+	    && argvars[3].v_type != VAR_UNKNOWN)
+	timeout = get_tv_number(&argvars[3]);
 
     server_name = get_tv_string_chk(&argvars[0]);
     if (server_name == NULL)
 	return;		/* type error; errmsg already given */
     keys = get_tv_string_buf(&argvars[1], buf);
 # ifdef WIN32
-    if (serverSendToVim(server_name, keys, &r, &w, expr, TRUE) < 0)
+    if (serverSendToVim(server_name, keys, &r, &w, expr, timeout, TRUE) < 0)
 # else
-    if (serverSendToVim(X_DISPLAY, server_name, keys, &r, &w, expr, 0, TRUE)
-									  < 0)
+    if (serverSendToVim(X_DISPLAY, server_name, keys, &r, &w, expr, timeout,
+								  0, TRUE) < 0)
 # endif
     {
 	if (r != NULL)
@@ -8555,13 +8559,15 @@ remote_common(typval_T *argvars, typval_T *rettv, int expr)
 	char_u		str[30];
 	char_u		*idvar;
 
-	sprintf((char *)str, PRINTF_HEX_LONG_U, (long_u)w);
-	v.di_tv.v_type = VAR_STRING;
-	v.di_tv.vval.v_string = vim_strsave(str);
 	idvar = get_tv_string_chk(&argvars[2]);
-	if (idvar != NULL)
+	if (idvar != NULL && *idvar != NUL)
+	{
+	    sprintf((char *)str, PRINTF_HEX_LONG_U, (long_u)w);
+	    v.di_tv.v_type = VAR_STRING;
+	    v.di_tv.vval.v_string = vim_strsave(str);
 	    set_var(idvar, &v.di_tv, FALSE);
-	vim_free(v.di_tv.vval.v_string);
+	    vim_free(v.di_tv.vval.v_string);
+	}
     }
 }
 #endif
@@ -8633,7 +8639,7 @@ f_remote_peek(typval_T *argvars UNUSED, typval_T *rettv)
 	rettv->vval.v_number = -1;
     else
     {
-	s = serverGetReply((HWND)n, FALSE, FALSE, FALSE);
+	s = serverGetReply((HWND)n, FALSE, FALSE, FALSE, 0);
 	rettv->vval.v_number = (s != NULL);
     }
 # else
@@ -8670,17 +8676,23 @@ f_remote_read(typval_T *argvars UNUSED, typval_T *rettv)
 
     if (serverid != NULL && !check_restricted() && !check_secure())
     {
+	int timeout = 0;
+
+	if (argvars[1].v_type != VAR_UNKNOWN)
+	    timeout = get_tv_number(&argvars[1]);
+
 # ifdef WIN32
 	/* The server's HWND is encoded in the 'id' parameter */
 	long_u		n = 0;
 
 	sscanf((char *)serverid, SCANF_HEX_LONG_U, &n);
 	if (n != 0)
-	    r = serverGetReply((HWND)n, FALSE, TRUE, TRUE);
+	    r = serverGetReply((HWND)n, FALSE, TRUE, TRUE, timeout);
 	if (r == NULL)
 # else
-	if (check_connection() == FAIL || serverReadReply(X_DISPLAY,
-		serverStrToWin(serverid), &r, FALSE) < 0)
+	if (check_connection() == FAIL
+		|| serverReadReply(X_DISPLAY, serverStrToWin(serverid),
+						       &r, FALSE, timeout) < 0)
 # endif
 	    EMSG(_("E277: Unable to read a server reply"));
     }

src/if_xcmdsrv.c

@@ -373,6 +373,7 @@ serverSendToVim(
     char_u	**result,		/* Result of eval'ed expression */
     Window	*server,		/* Actual ID of receiving app */
     Bool	asExpr,			/* Interpret as keystrokes or expr ? */
+    int		timeout,		/* seconds to wait or zero */
     Bool	localLoop,		/* Throw away everything but result */
     int		silent)			/* don't complain about no server */
 {
@@ -485,7 +486,8 @@ serverSendToVim(
     pending.nextPtr = pendingCommands;
     pendingCommands = &pending;
 
-    ServerWait(dpy, w, WaitForPend, &pending, localLoop, 600);
+    ServerWait(dpy, w, WaitForPend, &pending, localLoop,
+						  timeout > 0 ? timeout : 600);
 
     /*
      * Unregister the information about the pending command
@@ -790,6 +792,7 @@ WaitForReply(void *p)
 
 /*
  * Wait for replies from id (win)
+ * When "timeout" is non-zero wait up to this many seconds.
  * Return 0 and the malloc'ed string when a reply is available.
  * Return -1 if the window becomes invalid while waiting.
  */
@@ -798,13 +801,15 @@ serverReadReply(
     Display	*dpy,
     Window	win,
     char_u	**str,
-    int		localLoop)
+    int		localLoop,
+    int		timeout)
 {
     int		len;
     char_u	*s;
     struct	ServerReply *p;
 
-    ServerWait(dpy, win, WaitForReply, &win, localLoop, -1);
+    ServerWait(dpy, win, WaitForReply, &win, localLoop,
+						   timeout > 0 ? timeout : -1);
 
     if ((p = ServerReplyFind(win, SROP_Find)) != NULL && p->strings.ga_len > 0)
     {

src/main.c

@@ -3791,10 +3791,10 @@ cmdsrv_main(
 	    }
 	    else
 		ret = serverSendToVim(xterm_dpy, sname, *serverStr,
-						    NULL, &srv, 0, 0, silent);
+						  NULL, &srv, 0, 0, 0, silent);
 # else
 	    /* Win32 always works? */
-	    ret = serverSendToVim(sname, *serverStr, NULL, &srv, 0, silent);
+	    ret = serverSendToVim(sname, *serverStr, NULL, &srv, 0, 0, silent);
 # endif
 	    if (ret < 0)
 	    {
@@ -3854,11 +3854,11 @@ cmdsrv_main(
 		while (memchr(done, 0, numFiles) != NULL)
 		{
 # ifdef WIN32
-		    p = serverGetReply(srv, NULL, TRUE, TRUE);
+		    p = serverGetReply(srv, NULL, TRUE, TRUE, 0);
 		    if (p == NULL)
 			break;
 # else
-		    if (serverReadReply(xterm_dpy, srv, &p, TRUE) < 0)
+		    if (serverReadReply(xterm_dpy, srv, &p, TRUE, -1) < 0)
 			break;
 # endif
 		    j = atoi((char *)p);
@@ -3885,12 +3885,12 @@ cmdsrv_main(
 # ifdef WIN32
 	    /* Win32 always works? */
 	    if (serverSendToVim(sname, (char_u *)argv[i + 1],
-						    &res, NULL, 1, FALSE) < 0)
+						  &res, NULL, 1, 0, FALSE) < 0)
 # else
 	    if (xterm_dpy == NULL)
 		mch_errmsg(_("No display: Send expression failed.\n"));
 	    else if (serverSendToVim(xterm_dpy, sname, (char_u *)argv[i + 1],
-						 &res, NULL, 1, 1, FALSE) < 0)
+					       &res, NULL, 1, 0, 1, FALSE) < 0)
 # endif
 	    {
 		if (res != NULL && *res != NUL)

src/os_mswin.c

@@ -2401,6 +2401,7 @@ serverSendToVim(
     char_u	 **result,		/* Result of eval'ed expression */
     void	 *ptarget,		/* HWND of server */
     int		 asExpr,		/* Expression or keys? */
+    int		 timeout,		/* timeout in seconds or zero */
     int		 silent)		/* don't complain about no server */
 {
     HWND	target;
@@ -2444,7 +2445,7 @@ serverSendToVim(
 	return -1;
 
     if (asExpr)
-	retval = serverGetReply(target, &retcode, TRUE, TRUE);
+	retval = serverGetReply(target, &retcode, TRUE, TRUE, timeout);
 
     if (result == NULL)
 	vim_free(retval);
@@ -2521,14 +2522,17 @@ save_reply(HWND server, char_u *reply, int expr)
  * if "wait" is TRUE block until a message arrives (or the server exits).
  */
     char_u *
-serverGetReply(HWND server, int *expr_res, int remove, int wait)
+serverGetReply(HWND server, int *expr_res, int remove, int wait, int timeout)
 {
     int		i;
     char_u	*reply;
     reply_T	*rep;
     int		did_process = FALSE;
+    time_t	start;
+    time_t	now;
 
     /* When waiting, loop until the message waiting for is received. */
+    time(&start);
     for (;;)
     {
 	/* Reset this here, in case a message arrives while we are going
@@ -2584,6 +2588,10 @@ serverGetReply(HWND server, int *expr_res, int remove, int wait)
 #ifdef FEAT_TIMERS
 	    check_due_timer();
 #endif
+	    time(&now);
+	    if (timeout > 0 && (now - start) >= timeout)
+		break;
+
 	    /* Wait for a SendMessage() call to us.  This could be the reply
 	     * we are waiting for.  Use a timeout of a second, to catch the
 	     * situation that the server died unexpectedly. */

src/proto/if_xcmdsrv.pro

@@ -1,11 +1,11 @@
 /* if_xcmdsrv.c */
 int serverRegisterName(Display *dpy, char_u *name);
 void serverChangeRegisteredWindow(Display *dpy, Window newwin);
-int serverSendToVim(Display *dpy, char_u *name, char_u *cmd, char_u **result, Window *server, int asExpr, int localLoop, int silent);
+int serverSendToVim(Display *dpy, char_u *name, char_u *cmd, char_u **result, Window *server, int asExpr, int timeout, int localLoop, int silent);
 char_u *serverGetVimNames(Display *dpy);
 Window serverStrToWin(char_u *str);
 int serverSendReply(char_u *name, char_u *str);
-int serverReadReply(Display *dpy, Window win, char_u **str, int localLoop);
+int serverReadReply(Display *dpy, Window win, char_u **str, int localLoop, int timeout);
 int serverPeekReply(Display *dpy, Window win, char_u **str);
 void serverEventProc(Display *dpy, XEvent *eventPtr, int immediate);
 void server_parse_messages(void);

src/proto/os_mswin.pro

@@ -43,9 +43,9 @@ void serverInitMessaging(void);
 void serverSetName(char_u *name);
 char_u *serverGetVimNames(void);
 int serverSendReply(char_u *name, char_u *reply);
-int serverSendToVim(char_u *name, char_u *cmd, char_u **result, void *ptarget, int asExpr, int silent);
+int serverSendToVim(char_u *name, char_u *cmd, char_u **result, void *ptarget, int asExpr, int timeout, int silent);
 void serverForeground(char_u *name);
-char_u *serverGetReply(HWND server, int *expr_res, int remove, int wait);
+char_u *serverGetReply(HWND server, int *expr_res, int remove, int wait, int timeout);
 void serverProcessPendingMessages(void);
 char *charset_id2name(int id);
 char *quality_id2name(DWORD id);