patch 8.1.0499: :2vimgrep causes an ml_get error

Problem:    :2vimgrep causes an ml_get error
Solution:   Pass tomatch pointer instead of value. (Yegappan Lakshmanan)

src/ex_getln.c

@@ -483,6 +483,12 @@ may_do_incsearch_highlighting(
     if (search_first_line == 0)
 	// start at the original cursor position
 	curwin->w_cursor = is_state->search_start;
+    else if (search_first_line > curbuf->b_ml.ml_line_count)
+    {
+	// start after the last line
+	curwin->w_cursor.lnum = curbuf->b_ml.ml_line_count;
+	curwin->w_cursor.col = MAXCOL;
+    }
     else
     {
 	// start at the first line in the range

src/quickfix.c

@@ -5217,7 +5217,7 @@ vgr_match_buflines(
 	char_u	    *fname,
 	buf_T	    *buf,
 	regmmatch_T *regmatch,
-	long	    tomatch,
+	long	    *tomatch,
 	int	    duplicate_name,
 	int	    flags)
 {
@@ -5225,7 +5225,7 @@ vgr_match_buflines(
     long	lnum;
     colnr_T	col;
 
-    for (lnum = 1; lnum <= buf->b_ml.ml_line_count && tomatch > 0; ++lnum)
+    for (lnum = 1; lnum <= buf->b_ml.ml_line_count && *tomatch > 0; ++lnum)
     {
 	col = 0;
 	while (vim_regexec_multi(regmatch, curwin, buf, lnum,
@@ -5255,7 +5255,7 @@ vgr_match_buflines(
 		break;
 	    }
 	    found_match = TRUE;
-	    if (--tomatch == 0)
+	    if (--*tomatch == 0)
 		break;
 	    if ((flags & VGR_GLOBAL) == 0
 		    || regmatch->endpos[0].lnum > 0)
@@ -5464,7 +5464,7 @@ ex_vimgrep(exarg_T *eap)
 	    // Try for a match in all lines of the buffer.
 	    // For ":1vimgrep" look for first match only.
 	    found_match = vgr_match_buflines(qi, fname, buf, &regmatch,
-		    tomatch, duplicate_name, flags);
+		    &tomatch, duplicate_name, flags);
 
 	    if (using_dummy)
 	    {

src/testdir/test_quickfix.vim

@@ -2364,6 +2364,21 @@ func Test_vimgrep()
   call XvimgrepTests('l')
 endfunc
 
+" Test for incsearch highlighting of the :vimgrep pattern
+" This test used to cause "E315: ml_get: invalid lnum" errors.
+func Test_vimgrep_incsearch()
+  enew
+  set incsearch
+  call test_override("char_avail", 1)
+
+  call feedkeys(":2vimgrep assert test_quickfix.vim test_cdo.vim\<CR>", "ntx")
+  let l = getqflist()
+  call assert_equal(2, len(l))
+
+  call test_override("ALL", 0)
+  set noincsearch
+endfunc
+
 func XfreeTests(cchar)
   call s:setup_commands(a:cchar)
 

src/version.c

@@ -792,6 +792,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    499,
 /**/
     498,
 /**/