1 files changed, 94 insertions, 10 deletions

diff --git a/clang/lib/Driver/ToolChains/Gnu.cpp b/clang/lib/Driver/ToolChains/Gnu.cpp
index 7c0bcdcaf07..91076709fd7 100644
--- a/clang/lib/Driver/ToolChains/Gnu.cpp
+++ b/clang/lib/Driver/ToolChains/Gnu.cpp
@@ -2686,19 +2686,49 @@ void Generic_GCC::AddClangCXXStdlibIncludeArgs(const ArgList &DriverArgs,
   }
 }
 
-void
-Generic_GCC::addLibCxxIncludePaths(const llvm::opt::ArgList &DriverArgs,
-                                   llvm::opt::ArgStringList &CC1Args) const {
-  // FIXME: The Linux behavior would probaby be a better approach here.
-  addSystemInclude(DriverArgs, CC1Args,
-                   getDriver().SysRoot + "/usr/include/c++/v1");
+static std::string DetectLibcxxIncludePath(llvm::vfs::FileSystem &vfs,
+                                           StringRef base) {
+  std::error_code EC;
+  int MaxVersion = 0;
+  std::string MaxVersionString;
+  for (llvm::vfs::directory_iterator LI = vfs.dir_begin(base, EC), LE;
+       !EC && LI != LE; LI = LI.increment(EC)) {
+    StringRef VersionText = llvm::sys::path::filename(LI->path());
+    int Version;
+    if (VersionText[0] == 'v' &&
+        !VersionText.slice(1, StringRef::npos).getAsInteger(10, Version)) {
+      if (Version > MaxVersion) {
+        MaxVersion = Version;
+        MaxVersionString = VersionText;
+      }
+    }
+  }
+  return MaxVersion ? (base + "/" + MaxVersionString).str() : "";
 }
 
 void
-Generic_GCC::addLibStdCxxIncludePaths(const llvm::opt::ArgList &DriverArgs,
-                                      llvm::opt::ArgStringList &CC1Args) const {
-  // By default, we don't assume we know where libstdc++ might be installed.
-  // FIXME: If we have a valid GCCInstallation, use it.
+Generic_GCC::addLibCxxIncludePaths(const llvm::opt::ArgList &DriverArgs,
+                                   llvm::opt::ArgStringList &CC1Args) const {
+  const std::string& SysRoot = getDriver().SysRoot;
+  auto AddIncludePath = [&](std::string Path) {
+    std::string IncludePath = DetectLibcxxIncludePath(getVFS(), Path);
+    if (IncludePath.empty() || !getVFS().exists(IncludePath))
+      return false;
+    addSystemInclude(DriverArgs, CC1Args, IncludePath);
+    return true;
+  };
+  // Android never uses the libc++ headers installed alongside the toolchain,
+  // which are generally incompatible with the NDK libraries anyway.
+  if (!getTriple().isAndroid())
+    if (AddIncludePath(getDriver().Dir + "/../include/c++"))
+      return;
+  // If this is a development, non-installed, clang, libcxx will
+  // not be found at ../include/c++ but it likely to be found at
+  // one of the following two locations:
+  if (AddIncludePath(SysRoot + "/usr/local/include/c++"))
+    return;
+  if (AddIncludePath(SysRoot + "/usr/include/c++"))
+    return;
 }
 
 /// Helper to add the variant paths of a libstdc++ installation.
@@ -2734,6 +2764,60 @@ bool Generic_GCC::addLibStdCXXIncludePaths(
   return true;
 }
 
+bool
+Generic_GCC::addGCCLibStdCxxIncludePaths(const llvm::opt::ArgList &DriverArgs,
+                                         llvm::opt::ArgStringList &CC1Args) const {
+  // Use GCCInstallation to know where libstdc++ headers are installed.
+  if (!GCCInstallation.isValid())
+    return false;
+
+  // By default, look for the C++ headers in an include directory adjacent to
+  // the lib directory of the GCC installation. Note that this is expect to be
+  // equivalent to '/usr/include/c++/X.Y' in almost all cases.
+  StringRef LibDir = GCCInstallation.getParentLibPath();
+  StringRef InstallDir = GCCInstallation.getInstallPath();
+  StringRef TripleStr = GCCInstallation.getTriple().str();
+  const Multilib &Multilib = GCCInstallation.getMultilib();
+  const std::string GCCMultiarchTriple = getMultiarchTriple(
+      getDriver(), GCCInstallation.getTriple(), getDriver().SysRoot);
+  const std::string TargetMultiarchTriple =
+      getMultiarchTriple(getDriver(), getTriple(), getDriver().SysRoot);
+  const GCCVersion &Version = GCCInstallation.getVersion();
+
+  // The primary search for libstdc++ supports multiarch variants.
+  if (addLibStdCXXIncludePaths(LibDir.str() + "/../include",
+                               "/c++/" + Version.Text, TripleStr,
+                               GCCMultiarchTriple, TargetMultiarchTriple,
+                               Multilib.includeSuffix(), DriverArgs, CC1Args))
+    return true;
+
+  // Otherwise, fall back on a bunch of options which don't use multiarch
+  // layouts for simplicity.
+  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.Text,
+      InstallDir.str() + "/include/g++-v" + Version.MajorStr + "." +
+          Version.MinorStr,
+      InstallDir.str() + "/include/g++-v" + Version.MajorStr,
+  };
+
+  for (const auto &IncludePath : LibStdCXXIncludePathCandidates) {
+    if (addLibStdCXXIncludePaths(IncludePath, /*Suffix*/ "", TripleStr,
+                                 /*GCCMultiarchTriple*/ "",
+                                 /*TargetMultiarchTriple*/ "",
+                                 Multilib.includeSuffix(), DriverArgs, CC1Args))
+      return true;
+  }
+  return false;
+}
+
+void
+Generic_GCC::addLibStdCxxIncludePaths(const llvm::opt::ArgList &DriverArgs,
+                                      llvm::opt::ArgStringList &CC1Args) const {
+  addGCCLibStdCxxIncludePaths(DriverArgs, CC1Args);
+}
+
 llvm::opt::DerivedArgList *
 Generic_GCC::TranslateArgs(const llvm::opt::DerivedArgList &Args, StringRef,
                            Action::OffloadKind DeviceOffloadKind) const {