patch 8.2.3292: underscore in very magic pattern causes a hang

Problem:    Underscore in very magic pattern causes a hang.  Pattern with \V
            are case sensitive. (Yutao Yuan)
Solution:   Adjust condition for magicness and advance pointer. (Christian
            Brabandt, closes #8707, closes #8704, closes #8705)

src/search.c

@@ -445,7 +445,7 @@ pat_has_uppercase(char_u *pat)
 		return TRUE;
 	    p += l;
 	}
-	else if (*p == '\\' && magic_val == MAGIC_ON)
+	else if (*p == '\\' && magic_val <= MAGIC_ON)
 	{
 	    if (p[1] == '_' && p[2] != NUL)  // skip "\_X"
 		p += 3;
@@ -460,6 +460,8 @@ pat_has_uppercase(char_u *pat)
 	{
 	    if (p[1] != NUL)  // skip "_X" and %X
 		p += 2;
+	    else
+		p++;
 	}
 	else if (MB_ISUPPER(*p))
 	    return TRUE;

src/testdir/test_search.vim

@@ -1962,6 +1962,17 @@ func Test_pattern_is_uppercase_smartcase()
   call assert_equal(['abc', 'ABC', 'Abc', ''],
         \ getline(1, '$'))
 
+  call setline(1, input)
+  call cursor(1,1)
+  " \Vabc should match everything
+  %s/\Vabc//g
+  call assert_equal(['', '', '', ''], getline(1, '$'))
+
+  call setline(1, input + ['_abc'])
+  " _ matches normally
+  %s/\v_.*//g
+  call assert_equal(['abc', 'ABC', 'Abc', 'abC', ''], getline(1, '$'))
+
   set smartcase& ignorecase&
   bw!
 endfunc

src/version.c

@@ -755,6 +755,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    3292,
 /**/
     3291,
 /**/