[cfe-dev] Constant CF/NSString and Unicode

Jean-Daniel Dupas devlists at shadowlab.org
Wed Jul 9 23:50:55 PDT 2008

Le 10 juil. 08 à 07:56, Chris Lattner a écrit :

> On Jul 9, 2008, at 4:10 PM, Jean-Daniel Dupas wrote:
>> I just wonder if there is some kind of unicode support in
>> __builtin___CFStringMakeConstantString.
> In GCC or clang?  Clang doesn't have any unicode support yet.
>> In the current GCC version, when you compile an objc file, constant
>> strings that contains non-ascii chars are converted into utf-16
>> strings and a flag is set into the generated CFString.
> Ok.  Fariborz implemented that fwiw.
>> The fact that it works only for objc file look more like a design
>> decision than a technical limit, and this feature can easily be
>> extended to c files. In fact, I managed to implement this feature in
>> cc1 and it look like it works. (if I'm wrong, feel free to correct  
>> me).
>> And what about clang and unicode CFString ?
> I'm not sure what you mean, can you explain a bit more?
> -Chris

put this simple code snippet in cfstring.c :

#include <CoreFoundation/CoreFoundation.h>

int main(int argc, char **argv) {
   CFShowStr(CFSTR("hé hé hé"));
   CFShow(CFSTR("hé hé hé"));
   return 0;

if you compile this file using "gcc -o cfstring cfstring.c -framework  
CoreFoundation" and run it  you got:

Length 11
IsEightBit 1
HasLengthByte 0
HasNullByte 1
InlineContents 0
Allocator SystemDefault
Mutable 0
Contents 0x1ff2
h\u221a\u00a9 h\u221a\u00a9 h\u221a\u00a9

Now, if you compile this same file using

gcc -x objective-c -o cfstring cfstring.c -framework CoreFoundation

the output is:

Length 8
IsEightBit 0
HasLengthByte 0
HasNullByte 0
InlineContents 0
Allocator SystemDefault
Mutable 0
Contents 0x1fee
h\u00e9 h\u00e9 h\u00e9

Maybe I miss something, but I really do not understand the current  
As clang will probably implements this feature some day, I just wonder  
if it should duplicate the GCC behavior (emitting a warning and  
generating an ascii based CFString) or if it can be extended to  
support also UTF-16 CFString generation in plain C file.

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