divide_condition: warn about if (foo / 4) {

The condition "if (foo / 4) {" could be replaced with "if (foo >= 4) {"
which is what Smatch suggests, but a lot of them should be instead replaced
with "if ((foo % 4) == 0) {".

Signed-off-by: Dan Carpenter <[email protected]>

check_divide_condition.c

@@ -0,0 +1,46 @@
+/*
+ * Copyright (C) 2022 Dan Carpenter.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see http://www.gnu.org/copyleft/gpl.txt
+ */
+
+#include "smatch.h"
+#include "smatch_extra.h"
+
+static int my_id;
+
+static void match_condition1(struct expression *expr)
+{
+	char *left, *right;
+
+	if (expr->type != EXPR_BINOP || expr->op != '/')
+		return;
+
+	if (get_macro_name(expr->pos))
+		return;
+
+	left = expr_to_str(expr->left);
+	right = expr_to_str(expr->right);
+	sm_warning("replace divide condition '%s / %s' with '%s >= %s'",
+		   left, right, left, right);
+	free_string(left);
+	free_string(right);
+}
+
+void check_divide_condition(int id)
+{
+	my_id = id;
+
+	add_hook(&match_condition1, CONDITION_HOOK);
+}

check_list.h

@@ -186,6 +186,7 @@ CK(register_param_bits_set)
 CK(register_param_bits_clear)
 CK(check_do_while_loop_limit)
 CK(check_ida_alloc)
+CK(check_divide_condition)
 
 /* <- your test goes here */
 /* CK(register_template) */