Support g++ headers in include/g++

[greened]

Summary

Cray's gcc installation puts C++ headers in PREFIX/include/g++ without indicating a gcc version at all. Typically this is because the version is encoded somewhere in PREFIX.

[rsmith]

This needs a test.

lib/Driver/ToolChains/Linux.cpp

927–928

It'd be useful to say who this "some" is, so we can check whether this is still a valid concern in the future.

[greened]

lib/Driver/ToolChains/Linux.cpp

927–928

I will try to find out where we got the package from.

[greened]

Explain that Cray packages gcc such that headers are in include/g++.

[rsmith]

Looks good with an accompanying test. (You can probably copy whatever was added for the FreeScale line above.)

[greened]

Oops, I didn't realize this hadn't been formally accepted yet. Still learning the Phab process. Let me know if you want it reverted for a formal accept.

[rsmith]

In D53770#1297646, @greened wrote:

Oops, I didn't realize this hadn't been formally accepted yet. Still learning the Phab process. Let me know if you want it reverted for a formal accept.

No, this is fine.

lib/Driver/ToolChains/Linux.cpp

const std::string LibStdCXXIncludePathCandidates[] = {
       InstallDir.str() + "/include/g++-v" + Version.MajorStr + "." +
           Version.MinorStr,
       InstallDir.str() + "/include/g++-v" + Version.MajorStr,
       // Android standalone toolchain has C++ headers in yet another place.
       LibDir.str() + "/../" + TripleStr.str() + "/include/c++/" + Version.Text,
       // Freescale SDK C++ headers are directly in <sysroot>/usr/include/c++,
       // without a subdirectory corresponding to the gcc version.
       LibDir.str() + "/../include/c++",
+      // Some gcc installations put headers under "g++" without a
+      // version suffix.
+      LibDir.str() + "/../include/g++",
   };
 
   for (const auto &IncludePath : LibStdCXXIncludePathCandidates) {
     if (addLibStdCXXIncludePaths(IncludePath, /*Suffix*/ "", TripleStr,
                                  /*GCCMultiarchTriple*/ "",
                                  /*TargetMultiarchTriple*/ "",
                                  Multilib.includeSuffix(), DriverArgs, CC1Args))
       break;