_CP_SADDR returns a standard char* pointing to the first character of the string buffer within a CPSTR structure. Because _CP_SADDR is a macro, it can be used either to the left or right side of an assignment operator.
char* _CP_SADDR(CPSTR* string)
CPSTR * s = _CP_mkstr("hi");
_CP_SADDR(s)[1] = ’o’; /* replace 2nd character */
_CP_unix_env(); /* UNIX print environment */
_CP_TERM(s); /* null terminate */
printf("%s\n",_CP_SADDR(s));