patch 8.0.0643: when a pattern search is slow Vim becomes unusable commit https://github.com/vim/vim/commit/fbd0b0af6800f6ff89857863d6a07ea03f09ff6c Author: Bram Moolenaar <Bram@vim.org> Date: Sat Jun 17 18:44:21 2017 +0200 patch 8.0.0643: when a pattern search is slow Vim becomes unusable Problem: When 'hlsearch' is set and matching with the last search pattern is very slow, Vim becomes unusable. Cannot quit search by pressing CTRL-C. Solution: When the search times out set a flag and don't try again. Check for timeout and CTRL-C in NFA loop that adds states.

--- a/src/syntax.c
+++ b/src/syntax.c
@@ -3303,7 +3303,7 @@ syn_regexec(
 #endif
 
     rmp->rmm_maxcol = syn_buf->b_p_smc;
-    r = vim_regexec_multi(rmp, syn_win, syn_buf, lnum, col, NULL);
+    r = vim_regexec_multi(rmp, syn_win, syn_buf, lnum, col, NULL, NULL);
 
 #ifdef FEAT_PROFILE
     if (syn_time_on)