Reland 198fbcb8, "Driver: Don't look for libc++ headers in the install directory on Android.", which was reverted in b3249027.

Fixed the test case to set --sysroot, which lets it succeed in the case where
a directory named "/usr/include/c++/v1" or "/usr/local/include/c++/v1" exists.

Original commit message:
> The NDK uses a separate set of libc++ headers in the sysroot. Any headers
> in the installation directory are not going to work on Android, not least
> because they use a different name for the inline namespace (std::__1 instead
> of std::__ndk1).
>
> This effectively makes it impossible to produce a single toolchain that is
> capable of targeting both Android and another platform that expects libc++
> headers to be installed in the installation directory, such as Mac.
>
> In order to allow this scenario to work, stop looking for headers in the
> install directory on Android.

Differential Revision: https://reviews.llvm.org/D71154

1 files changed, 16 insertions, 11 deletions

diff --git a/clang/lib/Driver/ToolChains/Linux.cpp b/clang/lib/Driver/ToolChains/Linux.cpp
index 736a2d435ca..adacd705d83 100644
--- a/clang/lib/Driver/ToolChains/Linux.cpp
+++ b/clang/lib/Driver/ToolChains/Linux.cpp
@@ -888,20 +888,25 @@ static std::string DetectLibcxxIncludePath(llvm::vfs::FileSystem &vfs,
 void Linux::addLibCxxIncludePaths(const llvm::opt::ArgList &DriverArgs,
                                   llvm::opt::ArgStringList &CC1Args) const {
   const std::string& SysRoot = computeSysRoot();
-  const std::string LibCXXIncludePathCandidates[] = {
-      DetectLibcxxIncludePath(getVFS(), getDriver().Dir + "/../include/c++"),
-      // 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:
-      DetectLibcxxIncludePath(getVFS(), SysRoot + "/usr/local/include/c++"),
-      DetectLibcxxIncludePath(getVFS(), SysRoot + "/usr/include/c++") };
-  for (const auto &IncludePath : LibCXXIncludePathCandidates) {
+  auto AddIncludePath = [&](std::string Path) {
+    std::string IncludePath = DetectLibcxxIncludePath(getVFS(), Path);
     if (IncludePath.empty() || !getVFS().exists(IncludePath))
-      continue;
-    // Use the first candidate that exists.
+      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;
-  }
 }
 
 void Linux::addLibStdCxxIncludePaths(const llvm::opt::ArgList &DriverArgs,