Re: [Boost-users] [Unit Test] compiling fails on MacOS X

From: Rush Manbert (rush_at_[hidden])
Date: 2005-10-12 12:10:36

Gennadiy Rozental wrote:

>>Hi Gennadiy,
>>
>>I'm sorry for the screwup. It looks like I didn't capture the stderr
>>output in the text file. The attached file
>>is from another build attempt that fails updating those same 6 targets,
>>but it shows the undefined
>>symbol errors. If I go and look in the build directories, I can see that
>>    
>>
>
>I am no expect for Mac, but from an output it looks like this system, the 
>same as Windows, doesn't support unresolved symbols within shared libraries. 
>If you could confirm that this is true, I will have to update a Jamfile to 
>prevent these to be built and you should be using static libraries instead. 
>If it's not true - this is toolset issue.
>
>Gennadiy 
>
>  
>
It appears that the default treatment for undefined symbols is error, 
but there are a couple of ld
flags that can circumvent that.

Excerpt from "man ld":
      -undefined treatment
              Specifies  how  undefined  symbols are to be treated.  
treatment
              can be: error, warning, or suppress.  Which cause the  
treatment
              of  undefined symbols as either, errors, warnings, or 
suppresses
              the checking of undefined symbols.   The  default  is  to  
treat
              undefined  symbols  as  errors.   When  the environment 
variable
              MACOSX_DEPLOYMENT_TARGET is set to 10.3 or  higher then  
-unde-
              fined  dynamic_lookup  can  also  be used to allow any 
undefined
              symbols to be looked up dynamically at runtime.  Use of a 
binary
              built  with  this  flag  requires a system with a dynamic 
linker
              from Mac OS X 10.3 or later.  The flag  -undefined  
define_a_way
              can  also be used to cause the static linker to create a 
private
              definition for all undefined symbols.  This flag should 
only  be
              used  if  it  is known that the undefined symbols are not 
refer-
              enced as any use of them may cause a crash.

       -U sym Allow the symbol sym to be undefined, even if the -r flag 
is not
              given.  Produce an executable file if the only undefined 
symbols
              are those specified with -U.

              This option overlaps with a compiler option.   If  you  
use  the
              compiler  driver  cc(1) to invoke ld, invoke this option 
in this
              way: -Wl,-U,sym.

And since -U references -r:

       -r     Save  the  relocation  information in the output file so 
that it
              can be the subject of another ld run.  The resulting  
file  type
              is a Mach-O relocatable file (MH_OBJECT) if not otherwise 
speci-
              fied.  This flag also  prevents  final  definitions  from  
being
              given  to  common symbols, and suppresses the `undefined 
symbol'
              diagnostics.

So it looks like the dylibs can be built if the right flags are passed 
to ld. I would
try it, but I have no idea how to go about changing the jamfile, or even 
which
one to change. If you want me to test a modified jamfile, you could 
email it
with instructions to rush at manbert dot com.
- Rush