[cfe-dev] GNU runtime non-fragile ABI and cleanup

[David Chisnall]

On 31 Aug 2009, at 17:52, Fariborz Jahanian wrote:

> To have the effect on SL you need to provide both -fno-constant-
> cfstrings -fconstant-string-class=xx
> It is probably a gcc bug that it silently ignores -fconstant-string-
> class=xx all by itself.

In that case it is a gcc bug.  A test program that just prints the  
class of a constant string produces an NSCFString when compiled with - 
fconstant-string-class=NSConstantString on SL:

$ cat str.m
#include <stdio.h>
#include <objc/runtime.h>

int main(void)
{
	printf("%s\n", class_getName(((id)@"foo")->isa));
	return 0;
}
$ gcc -fconstant-string-class=NSConstantString str.m -lobjc
Undefined symbols:
   "___CFConstantStringClassReference", referenced from:
       _main in cc7mMxrY.o
ld: symbol(s) not found
collect2: ld returned 1 exit status
$ gcc --version
i686-apple-darwin10-gcc-4.2.1 (GCC) 4.2.1 (Apple Inc. build 5646)
Copyright (C) 2007 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There  
is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR  
PURPOSE.

This should be emitting an error that the NSConstantString class is  
not found.  If you link this against Cocoa, you get NSCFString as the  
output.

> Warning will indeed
> be useful to us.

Looking in clang-cc.cpp, it seems that other cases where incompatible  
options are specified are logging an error with fprintf and exiting.   
What is the correct way of issuing an option-ignored warning in clang- 
cc?  Or should this be handled in clang?

David