Make Gentoo GNU GCC Config override whitespace tolerant

[erichkeane]

Summary

The config-*triple* file handling isn't tolerant of leading/trailing whitespace, making it not terribly obvious when a single extraneous tab/space/etc will cause the override to be ignored. This patch simply trims the lines to ensure that it is tolerant of whitespace.

[craig.topper]

lib/Driver/ToolChains/Gnu.cpp

2176

Can we just do

Line = Line.trim()

so we won't have an extra StringRef and no one can misuse the untrimmed on in the future.

[erichkeane]

Oops, yeah, good suggestion.

[mgorny]

Is there any specific reason you need this? Since the file is autogenerated, I don't think it matters very much to allow extra whiespace. But then, I do not think it hurts, so feel free to do it. The code LGTM; note that I haven't tested it, however.

[erichkeane]

In D31996#727229, @mgorny wrote:

Is there any specific reason you need this? Since the file is autogenerated, I don't think it matters very much to allow extra whiespace. But then, I do not think it hurts, so feel free to do it. The code LGTM; note that I haven't tested it, however.

In my case, a misbehaving copy of SVN caused the test for this to have a '\r\n' line ending on Windows. I fixed my SVN, but also realized that tolerance for whitespace might be valuable, particularly since a human might decide to change this without the gcc-config tool and neglect a trailing space. It scared me that this was a condition where it would APPEAR to work well (ie, configure it to the 'latest', but not realize it is being ignored), then be surprised later.

[mgorny]

Well, I've just checked gcc-config sources and it seems that it sources the file through bash, and gets the resulting ${CURRENT}. While I don't think we ought to do complete bash support here, I guess allowing the same degree of whitespace bash does makes sense.

[erichkeane]

Forgot the "DifferentialRevision" in the commit message, but added it as related here.

lib/Driver/ToolChains/Gnu.cpp

bool Generic_GCC::GCCInstallationDetector::ScanGentooGccConfig(
     StringRef CandidateTriple, bool NeedsBiarchSuffix) {
   llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> File =
       D.getVFS().getBufferForFile(D.SysRoot + "/etc/env.d/gcc/config-" +
                                   CandidateTriple.str());
   if (File) {
     SmallVector<StringRef, 2> Lines;
     File.get()->getBuffer().split(Lines, "\n");
     for (StringRef Line : Lines) {
+      Line = Line.trim();
       // CURRENT=triple-version
       if (Line.consume_front("CURRENT=")) {
         const std::pair<StringRef, StringRef> ActiveVersion =
           Line.rsplit('-');
         // Note: Strictly speaking, we should be reading
         // /etc/env.d/gcc/${CURRENT} now. However, the file doesn't
         // contain anything new or especially useful to us.
         const std::string GentooPath = D.SysRoot + "/usr/lib/gcc/" +