[MacPorts] #53931: clang's ld doesn't recognise "-lto_library" flag on 10.6

[MacPorts]

#53931: clang's ld doesn't recognise "-lto_library" flag on 10.6
-------------------------------------------------+-------------------------
  Reporter:  mojca                               |      Owner:  jeremyhu
      Type:  defect                              |     Status:  new
  Priority:  Normal                              |  Milestone:
 Component:  ports                               |    Version:
Resolution:                                      |   Keywords:  snowleopard
      Port:  clang-3.9 clang-4.0 llvm-3.9        |
  llvm-4.0                                       |
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Comment (by jeremyhu):

 clang seems at first glance to be doing the right thing here:


 {{{
   unsigned Version[5] = {0, 0, 0, 0, 0};
   if (Arg *A = Args.getLastArg(options::OPT_mlinker_version_EQ)) {
     if (!Driver::GetReleaseVersion(A->getValue(), Version))
       D.Diag(diag::err_drv_invalid_version_number) <<
 A->getAsString(Args);
   }

    ...

   // Use -lto_library option to specify the libLTO.dylib path. Try to find
   // it in clang installed libraries. ld64 will only look at this argument
   // when it actually uses LTO, so libLTO.dylib only needs to exist at
 link
   // time if ld64 decides that it needs to use LTO.
   // Since this is passed unconditionally, ld64 will never look for
 libLTO.dylib
   // next to it. That's ok since ld64 using a libLTO.dylib not matching
 the
   // clang version won't work anyways.
   if (Version[0] >= 133) {
     // Search for libLTO in <InstalledDir>/../lib/libLTO.dylib
     StringRef P = llvm::sys::path::parent_path(D.Dir);
     SmallString<128> LibLTOPath(P);
     llvm::sys::path::append(LibLTOPath, "lib");
     llvm::sys::path::append(LibLTOPath, "libLTO.dylib");
     CmdArgs.push_back("-lto_library");
     CmdArgs.push_back(C.getArgs().MakeArgString(LibLTOPath));
   }
 }}}

 And in the `-v` output pasted above, I see `-target-linker-version 136`
 being passed to clang, so the issue is that it thinks the linker is a
 newer version than it really is.

--
Ticket URL: <https://trac.macports.org/ticket/53931#comment:20>
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