Make the Linux support for finding libc++ somewhat less braindead.

Now instead of just looking in the system root for it, we also look
relative to the clang binary's directory. This should "just work" in
almost all cases. I've added test cases accordingly.

This is probably *very* worthwhile to backport to the 3.4 branch so that
folks can check it out, build it, and use that as their host compiler
going forward.

llvm-svn: 199632

2 files changed, 45 insertions, 6 deletions

diff --git a/clang/lib/Driver/ToolChains.cpp b/clang/lib/Driver/ToolChains.cpp
index c0563469c1c..e364fa7ba31 100644
--- a/clang/lib/Driver/ToolChains.cpp
+++ b/clang/lib/Driver/ToolChains.cpp
@@ -2945,9 +2945,24 @@ void Linux::AddClangCXXStdlibIncludeArgs(const ArgList &DriverArgs,
 
   // Check if libc++ has been enabled and provide its include paths if so.
   if (GetCXXStdlibType(DriverArgs) == ToolChain::CST_Libcxx) {
-    // libc++ is always installed at a fixed path on Linux currently.
-    addSystemInclude(DriverArgs, CC1Args,
-                     getDriver().SysRoot + "/usr/include/c++/v1");
+    const std::string LibCXXIncludePathCandidates[] = {
+      // The primary location is within the Clang installation.
+      // FIXME: We shouldn't hard code 'v1' here to make Clang future proof to
+      // newer ABI versions.
+      getDriver().Dir + "/../include/c++/v1",
+
+      // We also check the system as for a long time this is the only place Clang looked.
+      // FIXME: We should really remove this. It doesn't make any sense.
+      getDriver().SysRoot + "/usr/include/c++/v1"
+    };
+    for (unsigned i = 0; i < llvm::array_lengthof(LibCXXIncludePathCandidates);
+         ++i) {
+      if (!llvm::sys::fs::exists(LibCXXIncludePathCandidates[i]))
+        continue;
+      // Add the first candidate that exists.
+      addSystemInclude(DriverArgs, CC1Args, LibCXXIncludePathCandidates[i]);
+      break;
+    }
     return;
   }
 
@@ -2971,7 +2986,7 @@ void Linux::AddClangCXXStdlibIncludeArgs(const ArgList &DriverArgs,
                                MIPSABIDirSuffix, DriverArgs, CC1Args))
     return;
 
-  const std::string IncludePathCandidates[] = {
+  const std::string LibStdCXXIncludePathCandidates[] = {
     // Gentoo is weird and places its headers inside the GCC install, so if the
     // first attempt to find the headers fails, try these patterns.
     InstallDir.str() + "/include/g++-v" + Version.MajorStr + "." +
@@ -2984,8 +2999,9 @@ void Linux::AddClangCXXStdlibIncludeArgs(const ArgList &DriverArgs,
     LibDir.str() + "/../include/c++",
   };
 
-  for (unsigned i = 0; i < llvm::array_lengthof(IncludePathCandidates); ++i) {
-    if (addLibStdCXXIncludePaths(IncludePathCandidates[i],
+  for (unsigned i = 0; i < llvm::array_lengthof(LibStdCXXIncludePathCandidates);
+       ++i) {
+    if (addLibStdCXXIncludePaths(LibStdCXXIncludePathCandidates[i],
                                  TripleStr + MIPSABIDirSuffix + BiarchSuffix,
                                  DriverArgs, CC1Args))
       break;
diff --git a/clang/test/Driver/linux-header-search.cpp b/clang/test/Driver/linux-header-search.cpp
index 8955ed71d3c..84bfd584809 100644
--- a/clang/test/Driver/linux-header-search.cpp
+++ b/clang/test/Driver/linux-header-search.cpp
@@ -1,6 +1,29 @@
 // General tests that the header search paths detected by the driver and passed
 // to CC1 are sane.
 //
+// Test a simulated installation of libc++ on Linux, both through sysroot and
+// the installation path of Clang.
+// RUN: %clang -no-canonical-prefixes %s -### -fsyntax-only 2>&1 \
+// RUN:     -target x86_64-unknown-linux-gnu \
+// RUN:     -stdlib=libc++ \
+// RUN:     -ccc-install-dir %S/Inputs/basic_linux_tree/usr/bin \
+// RUN:     --sysroot=%S/Inputs/basic_linux_libcxx_tree \
+// RUN:   | FileCheck --check-prefix=CHECK-BASIC-LIBCXX-SYSROOT %s
+// CHECK-BASIC-LIBCXX-SYSROOT: "{{[^"]*}}clang{{[^"]*}}" "-cc1"
+// CHECK-BASIC-LIBCXX-SYSROOT: "-isysroot" "[[SYSROOT:[^"]+]]"
+// CHECK-BASIC-LIBCXX-SYSROOT: "-internal-isystem" "[[SYSROOT]]/usr/include/c++/v1"
+// CHECK-BASIC-LIBCXX-SYSROOT: "-internal-isystem" "[[SYSROOT]]/usr/local/include"
+// RUN: %clang -no-canonical-prefixes %s -### -fsyntax-only 2>&1 \
+// RUN:     -target x86_64-unknown-linux-gnu \
+// RUN:     -stdlib=libc++ \
+// RUN:     -ccc-install-dir %S/Inputs/basic_linux_libcxx_tree/usr/bin \
+// RUN:     --sysroot=%S/Inputs/basic_linux_libcxx_tree \
+// RUN:   | FileCheck --check-prefix=CHECK-BASIC-LIBCXX-INSTALL %s
+// CHECK-BASIC-LIBCXX-INSTALL: "{{[^"]*}}clang{{[^"]*}}" "-cc1"
+// CHECK-BASIC-LIBCXX-INSTALL: "-isysroot" "[[SYSROOT:[^"]+]]"
+// CHECK-BASIC-LIBCXX-INSTALL: "-internal-isystem" "[[SYSROOT]]/usr/bin/../include/c++/v1"
+// CHECK-BASIC-LIBCXX-INSTALL: "-internal-isystem" "[[SYSROOT]]/usr/local/include"
+//
 // Test a very broken version of multiarch that shipped in Ubuntu 11.04.
 // RUN: %clang -no-canonical-prefixes %s -### -fsyntax-only 2>&1 \
 // RUN:     -target i386-unknown-linux \