You can't use string functions if you aren't actually dealing with strings. You have to have a null character on the end of each for it to be considered a string. Say you pass an array of six characters, and it's really a string, so it's actually got seven characters total, just for the sake of argument:
Start looking at that, and see if that's really what you had in mind.
void foo( char bar )
char baz[ strlen( bar ) = 6, 6 / 3 = 2, baz = 2 ];
... now assume you actually make 'baz' a string ...
... that leaves you 1 usable character ...
for( x = 0; x < strlen baz = 1; x++ )
... whatever you're doing here is only going to happen to 1 character, so you don't need a loop ...