NSString retain crash

[Luboš Doležel]

Hi,

I have a problem where setting NSCell's value to a string crashes. I've 
tracked to problem down to a simple test that reproduces the crash:

NSString* str = @"test";
[str retain];

Backtrace:

#0  objc_msg_lookup_internal (receiver=<optimized out>, 
selector=<optimized out>, receiver=<optimized out>, selector=<optimized 
out>, sender=<optimized out>) at sendmsg2.c:66
#1  objc_msg_lookup (receiver=<optimized out>, selector=<optimized 
out>) at sendmsg2.c:398
#2  0x0000000000400796 in main () at str-retain.m:6

Why does the retain call cause a crash? I've learned that such constant 
strings don't use refcounting internally, but I don't think it should 
crash anyway.

Thanks!
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Luboš Doležel