Bug #165: Deletion of unnecessary null pointer checks

The function "free" performs input parameter validation.
http://pubs.opengroup.org/onlinepubs/9699919799/functions/free.html

It is therefore not needed to check a passed pointer before this function call.
A corresponding update suggestion was generated by the software "Coccinelle"
from the following semantic patch approach.
http://coccinelle.lip6.fr/

@Remove_unnecessary_pointer_checks1@
expression x;
@@
-if (x != \(0 \| NULL\))
    free(x);

@Remove_unnecessary_pointer_checks2@
expression x;
@@
-if (x != \(0 \| NULL\)) {
    free(x);
    x = \(0 \| NULL\);
-}

@Remove_unnecessary_pointer_checks3@
expression a, b;
@@
-if (a != \(0 \| NULL\) && b != \(0 \| NULL\))
+if (a)
    free(b);

@Remove_unnecessary_pointer_checks4@
expression a, b;
@@
-if (a != \(0 \| NULL\) && b != \(0 \| NULL\)) {
+if (a) {
    free(b);
    b = \(0 \| NULL\);
 }

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>

main.c

@@ -810,8 +810,7 @@ int main(int argc, char **argv)
 				filename[len-1] = '\0';
 			check_add_file(filename);
 		}
-		if (filename != NULL)
-			free(filename);
+		free(filename);
 	}
 
 	for (i = 0; i < options->filecnt; i++) {