_CP_trim is equivalent to the result = trim(string) BASIC statement.
int _CP_trim(CPSTR** result, CPSTR* string)
This function returns -1 if an error occurs. The error code is contained in _CP_errno.
/* Prints "3". */
CPSTR * s = _CP_mkstr(" 3 ");
_CP_trim(&s,s);
_CP_print(s);