Why do NSString and NSLog appear to handle

Question

Apple\'s String Format Specifiers document claims,

The format specifiers supported by the NSString formatting methods and CFString formatting function

Answer 1

On Mac OS X, <machine/_types.h> defines wchar_t as int, so it's four bytes (32 bits) on all currently-supported architectures.

As you note, the printf(3) manpage defines %S as equivalent to %ls, which takes a pointer to some wchar_t characters (wchar_t *).

The Cocoa documentation you linked to (and its CF equivalent), however, does define %S separately:

• %S: Null-terminated array of 16-bit Unicode characters

Emphasis added. Also, the same goes for %C.

So, this is not a bug. CF and Cocoa interpret %S and %C differently from how printf and its cousins interpret them. CF and Cocoa treat the character(s) as UTF-16, whereas printf (presumably) treats them as UTF-32.

The CF/Cocoa interpretation is more useful when working with Core Services, as some APIs (such as the File Manager) will hand you text as an array of UniChars, not a CFString; as long as you null-terminate that array, you can use it with %S to print the string.