patch 8.1.0098: segfault when pattern with z() is very slow commit https://github.com/vim/vim/commit/bcf9442307075bac40d44328c8bf7ea21857b138 Author: Bram Moolenaar <Bram@vim.org> Date: Sat Jun 23 14:21:42 2018 +0200 patch 8.1.0098: segfault when pattern with \z() is very slow Problem: Segfault when pattern with \z() is very slow. Solution: Check for NULL regprog. Add "nfa_fail" to test_override() to be able to test this. Fix that 'searchhl' resets called_emsg.

--- a/src/syntax.c
+++ b/src/syntax.c
@@ -3327,6 +3327,12 @@ syn_regexec(
 	profile_start(&pt);
 #endif
 
+    if (rmp->regprog == NULL)
+	// This can happen if a previous call to vim_regexec_multi() tried to
+	// use the NFA engine, which resulted in NFA_TOO_EXPENSIVE, and
+	// compiling the pattern with the other engine fails.
+	return FALSE;
+
     rmp->rmm_maxcol = syn_buf->b_p_smc;
     r = vim_regexec_multi(rmp, syn_win, syn_buf, lnum, col,
 #ifdef FEAT_RELTIME