Re: NSString lowercaseString

[David Chisnall]

On 1 Aug 2012, at 09:50, Sebastian Reitenbach wrote:

> I "enhanced" my test program a bit, and compared output when running on Linux 
> and OpenBSD:
> 
> #import <Foundation/Foundation.h>
> 
> 
> int main(int argc, char *argv[]) {
> NSLog(@"Lowercase: %@", [[NSString stringWithString:@"TöÖst"] 
> lowercaseString]);
> 
> }

On closer inspection, there is a bug here, but not where you think it is...

Try this test case:

$ cat tolower.m #import <Foundation/Foundation.h>
#import <wctype.h>


int main(int argc, char *argv[]) {
        [NSAutoreleasePool new];
        NSString *l = [@"TöÖst" lowercaseString];
        NSLog(@"Lowercase: %@", l);
        NSLog(@"Lowercase: %s", [l UTF8String]);
        for (int i=0 ; i<[l length] ; i++)
        {
                int c = [l characterAtIndex: i];
                NSLog(@"%c %d", c,c);
        }
}
$ clang tolower.m  -lgnustep-base
$ ./a.out
2012-07-31 19:23:44.810 a.out[69751] Lowercase: t??st
2012-07-31 19:23:44.813 a.out[69751] Lowercase: tööst
2012-07-31 19:23:44.813 a.out[69751] t 116
2012-07-31 19:23:44.813 a.out[69751] ? 246
2012-07-31 19:23:44.814 a.out[69751] ? 246
2012-07-31 19:23:44.814 a.out[69751] s 115
2012-07-31 19:23:44.814 a.out[69751] t 116

The error appears to be in converting the 16-bit unicode string that is the 
result of lowercaseString for display.  Note the values that are being returned 
in characterAtIndex: - these are the correct unicode values, but attempting to 
display them  is failing because the terminal is expecting UTF-8, not UCS16 
(and 246 is not a valid 8-bit UTF-8 character).  It seems that NSLog is just 
truncating the string, rather than translating it into the string locale that 
the terminal expects.

David

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