Driver: Don't mix system tools with devtoolset tools on RHEL

[tstellar]

Summary

On RHEL, devtoolset provides a more up-to-date toolchain than the base
install, and we want to make sure all the tools use are from the same
toolchain.

[tstellar]

Ping.u1

[tstellar]

Ping.

[tstellar]

Ping.

[tstellar]

Ping.

[bruno]

Is there a way to test this?

lib/Driver/ToolChains/Linux.cpp

220

You can remove the curly braces here.

[tstellar]

Replaced the if (Distro.isRedhat()) check with a string compare on the
GCC installation lib. This narrows the scope of the fix and also makes
it possible to write a test case. The code that detects distros ignores
sysroot and looks in /etc of the test system, which makes it impossible to
write a portable lit test to verify distro specific behavior.

[bruno]

LGTM, thanks!

lib/Driver/ToolChains/Linux.cpp

Linux::Linux(const Driver &D, const llvm::Triple &Triple, const ArgList &Args)
   // FIXME: This seems unlikely to be Linux-specific.
   ToolChain::path_list &PPaths = getProgramPaths();
   PPaths.push_back(Twine(GCCInstallation.getParentLibPath() + "/../" +
                          GCCInstallation.getTriple().str() + "/bin")
                        .str());
 
   Distro Distro(D.getVFS());
 
+  if (Distro.IsRedhat()) {
+    // On RHEL, we want to add a bin directory that is relative to the detected
+    // gcc install, because if we are using devtoolset gcc then we want to
+    // use other tools from devtoolset (e.g. ld) instead of the standard system
+    // tools.
+    PPaths.push_back(Twine(GCCInstallation.getParentLibPath() +
+                     "/../bin").str());
+  }
+
   if (Distro.IsOpenSUSE() || Distro.IsUbuntu()) {
     ExtraOpts.push_back("-z");
     ExtraOpts.push_back("relro");
   }
 
   if (Arch == llvm::Triple::arm || Arch == llvm::Triple::thumb)
     ExtraOpts.push_back("-X");