[MacPorts] #34288: clang ports use the old/dated libstdc++ from the host (gcc-4.2 based)

[MacPorts]

#34288: clang ports use the old/dated libstdc++ from the host (gcc-4.2 based)
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  Reporter:  christophe.prudhomme@…                                    |       Owner:  jeremyhu@…           
      Type:  defect                                                    |      Status:  closed               
  Priority:  Normal                                                    |   Milestone:                       
 Component:  ports                                                     |     Version:  2.0.4                
Resolution:  fixed                                                     |    Keywords:                       
      Port:  clang-2.9 clang-3.0 clang-3.1 clang-3.2 libstdc++ libc++  |  
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Comment(by jeremyhu@…):

 Replying to [comment:25 stephen@…]:
 > Can some please explain what the new changes are? I see that installing
 clang >= 3.0 now also installs headers from libc++ in
 /opt/local/libexec/llvm-3.1/lib/c++/v1 and that's where mp-clang will be
 looking for standard library headers. But as far as I can tell, it doesn't
 have a matching libc++.dylib and still links against the system one in
 /usr/lib.

 Yes.

 > Is this intended and safe? The 2 sets of v1 headers are not the same.
 Can the difference cause any runtime issue?

 I've been told by our internal developers of the C++ runtime that this is
 the correct way to do it.  Using multiple versions of the runtime *will*
 cause runtime issues as seen in #35770 which is why I never introduced the
 runtimes and will be removing them from the gcc ports.

 > Also I am trying this in OS X 10.7 which is shipped with libc++. What
 happens in 10.6? Does MacPorts installs a copy of libc++ (and the ABI lib)
 with clang?

 Nope.  If you want to use libc++ on Snow Leopard, you will need to install
 it yourself as detailed on http://libcxx.llvm.org

 Doing it this way will ensure that anything you build on SL will be
 compatible with Lion.

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Ticket URL: <https://trac.macports.org/ticket/34288#comment:26>
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