HEre is a stack trace.  I can give you args for whatever function, etc.  Just ask.  
I posted a hack to unix_canonicalize_host_name() that gets rid of the problem for me in
another email. 
Stack Trace
     _kevent,             FP=7fff5fbfbe60
     __mdns_query_mDNSResponder, FP=7fff5fbfbe60
     __mdns_search,       FP=7fff5fbfbf20
     __mdns_addrinfo,     FP=7fff5fbfc080
     _search_addrinfo,    FP=7fff5fbfc110
     _si_addrinfo,        FP=7fff5fbfc1f0
     _getaddrinfo,        FP=7fff5fbfc270
C    unix_canonicalize_host_name, FP=7fff5fbfc3e0
C    canonicalize_host_name, FP=7fff5fbfc400
C    x_canonicalize_console_connection, FP=7fff5fbfc4a0
C    x_canonicalize_device_connection, FP=7fff5fbfc540
C    canonicalize_device_connection, FP=7fff5fbfc580
C    Ffind_device,        FP=7fff5fbfc610
C    Fmake_device,        FP=7fff5fbfc700
C    Ffuncall,            FP=7fff5fbfc830
C    execute_optimized_program, FP=7fff5fbfcb70
C    funcall_compiled_function, FP=7fff5fbfcc70
C    Feval,               FP=7fff5fbfcf20
C    condition_case_1,    FP=7fff5fbfd0b0
C    condition_case_3,    FP=7fff5fbfd130
C    execute_rare_opcode, FP=7fff5fbfd230
C    execute_optimized_program, FP=7fff5fbfd580
C    funcall_compiled_function, FP=7fff5fbfd680
C    Feval,               FP=7fff5fbfd930
C    condition_case_1,    FP=7fff5fbfdac0
C    top_level_1,         FP=7fff5fbfdae0
C    internal_catch,      FP=7fff5fbfdc10
C    initial_command_loop, FP=7fff5fbfdc30
C    ...21_5_b29_i386_apple_darwin10_4_0, FP=7fff5fbfdd00
On Jul 24, 2010, at 8:14 AM, Stephen J. Turnbull wrote:
 Hamish Macdonald writes:
 
> However, I wonder why xemacs is trying to resolve this address.
> Local X applications on my system don't appear to do a DNS lookup
> when I use a display name like "/tmp/foo/bar/baz:0", so why does
> xemacs?
 
 I dunno.  If you've got the time, I would appreciate it if you'd set a
 breakpoint on getaddrinfo and tell me what's on the C stack and on the
 Lisp stack (use the lbt function defined in .gdbinit) when getaddrinfo
 gets called on such a thing.  If not, I'll get to it (I have a Mac
 with reasonably fresh Apple libraries installed), but probably that
 will be Real Soon Now. :-(
 
> Is it possible that either XEmacs is not using the locally
> installed XLIB library?
 
 No.  XEmacs always uses a toolkit; currently supported are Xt and GTK+
 v1 (oops, but there you go).  I conjecture that XEmacs wants to know
 something about the display's network aspect, but I don't have a good
 guess as to what.
 
> Is XEmacs performing its own interpretation of the DISPLAY
> environment variable (that would be a bad idea).
 
 Well, for one thing, the DISPLAY environment variable is not the only
 way to specify a display to XEmacs.  This can be done with the
 -display command line flag as well as `make-frame-on-display'.
 
 Unfortunately, it is REQUIRED for robust operation in the X
 environment that a program do its own parsing of such things.  X does
 *no* sanity checking on arguments in most functions, and it often
 leaves the restrictions on arguments undocumented.[1]
 
 Footnotes: 
 [1]  That's why I'm an XEmacs developer, because it was easier to
 debug an X crash due to a plausible but illegal argument in XEmacs
 than it was to debug the same bug in Emacs.
  
-- 
✐Richard Cook   
✇ Lawrence Livermore National Laboratory
Bldg-453 Rm-4024, Mail Stop L-557        
7000 East Avenue,  Livermore, CA, 94550, USA
☎ (office) (925) 423-9605    
☎ (fax) (925) 423-6961
---
Information Management & Graphics Grp., Services & Development Div., Integrated
Computing & Communications Dept.
(opinions expressed herein are mine and not those of LLNL)
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