Application crashes when calling -retain on NSSmallInt

[Stefan Bidigaray]

I'm getting the following crash when call retain on an NSSmallInt:

#0  0x2880179b in thr_kill () from /lib/libc.so.7
#1  0x2878ebeb in raise () from /lib/libthr.so.3
#2  0x288d6b06 in abort () from /lib/libc.so.7
#3  0x286c7285 in objc_exception_throw ()
   from /usr/local/lib/libobjc.so.4.6
#4  0x282c5a64 in -[NSException raise] (self=0x2b1b0d28,
    _cmd=0x28649f08) at NSException.m:972
#5  0x282c4bf5 in +[NSException raise:format:arguments:] (
    self=0x28649de0, _cmd=0x28649e78, name=0x28649d28,
    format=0x2868ce78,
    argList=0xbfbfea8c
"\027êZ(\226v[(á1w(°ê¿¿\034\0374(è\f\033+\020\020e(") at
NSException.m:854
#6  0x282c4af9 in +[NSException raise:format:] (self=0x28649de0,
    _cmd=0x2868cf20, name=0x28649d28, format=0x2868ce78)
    at NSException.m:840
#7  0x28471292 in GSFFIInvocationCallback (cif=0x2b0810b0,
    retp=0xbfbfeba8, args=0xbfbfeb70, user=0x2b1b0ce8)
    at GSFFIInvocation.m:545
#8  0x28d2116d in ffi_call () from /usr/local/lib/libffi.so.6
#9  0x28d21796 in ffi_call_SYSV () from /usr/local/lib/libffi.so.6
#10 0x2873fba8 in CFGetTypeID (cf=0xfffffff5) at CFRuntime.c:322
#11 0x2874044c in CFRetain (cf=0xfffffff5) at CFRuntime.c:367
#12 0x08048885 in main ()

The test application is:

#import <Foundation/Foundation.h>
#include <CoreFoundation/CoreFoundation.h>

int main (void)
{
  CFTypeRef obj = CFRetain ([NSNumber numberWithInt: -6]);

  CFRelease (obj);
  return 0;
}

Does anyone have any idea where I should go to debug this?  I'm using
FreeBSD-10.1 with Clang 3.4.1 and libobjc2 1.7.  I'm trying to create a
test case for the latest commit to CoreBase and just hit a metaphorical wall.

One thing to note is that CoreBase calls -retain by using the
functions in runtime.h, not through any sort of Objective-C code.