From ec976d3be4e78dbbb019b3be941066f74e826880 Mon Sep 17 00:00:00 2001
From: Sungkeun Cho <scho@fb.com>
Date: Fri, 4 Jun 2021 09:03:50 -0700
Subject: [PATCH] Apply patch for finding correct C++ header from Apple SDKs

Reviewed By: jvillard

Differential Revision: D28899204

fbshipit-source-id: c27c4d5dc
---
 facebook-clang-plugins/clang/setup.sh         |  1 +
 .../clang/src/sysroot_cpp_headers.patch       | 58 +++++++++++++++++++
 2 files changed, 59 insertions(+)
 create mode 100644 facebook-clang-plugins/clang/src/sysroot_cpp_headers.patch

diff --git a/facebook-clang-plugins/clang/setup.sh b/facebook-clang-plugins/clang/setup.sh
index 2d7297e97..e16431af8 100755
--- a/facebook-clang-plugins/clang/setup.sh
+++ b/facebook-clang-plugins/clang/setup.sh
@@ -17,6 +17,7 @@ CLANG_PREBUILD_PATCHES=(
     "$SCRIPT_DIR/src/mangle_suppress_errors.patch"
     "$SCRIPT_DIR/src/AArch64SVEACLETypes.patch"
     "$SCRIPT_DIR/src/benchmark_register.patch"
+    "$SCRIPT_DIR/src/sysroot_cpp_headers.patch"
 )
 CLANG_PREFIX="$SCRIPT_DIR/install"
 CLANG_INSTALLED_VERSION_FILE="$SCRIPT_DIR/installed.version"
diff --git a/facebook-clang-plugins/clang/src/sysroot_cpp_headers.patch b/facebook-clang-plugins/clang/src/sysroot_cpp_headers.patch
new file mode 100644
index 000000000..516c14549
--- /dev/null
+++ b/facebook-clang-plugins/clang/src/sysroot_cpp_headers.patch
@@ -0,0 +1,58 @@
+--- a/llvm-project/clang/lib/Driver/ToolChains/Darwin.cpp
++++ b/llvm-project/clang/lib/Driver/ToolChains/Darwin.cpp
+@@ -2021,20 +2021,41 @@
+
+   switch (GetCXXStdlibType(DriverArgs)) {
+   case ToolChain::CST_Libcxx: {
+-    // On Darwin, libc++ is installed alongside the compiler in
+-    // include/c++/v1, so get from '<install>/bin' to '<install>/include/c++/v1'.
+-    {
+-      llvm::SmallString<128> P = llvm::StringRef(getDriver().getInstalledDir());
+-      // Note that P can be relative, so we have to '..' and not parent_path.
+-      llvm::sys::path::append(P, "..", "include", "c++", "v1");
+-      addSystemInclude(DriverArgs, CC1Args, P);
+-    }
+-    // Also add <sysroot>/usr/include/c++/v1 unless -nostdinc is used,
+-    // to match the legacy behavior in CC1.
+-    if (!DriverArgs.hasArg(options::OPT_nostdinc)) {
+-      llvm::SmallString<128> P = Sysroot;
+-      llvm::sys::path::append(P, "usr", "include", "c++", "v1");
+-      addSystemInclude(DriverArgs, CC1Args, P);
++    // On Darwin, libc++ can be installed in one of the following two places:
++    // 1. Alongside the compiler in         <install>/include/c++/v1
++    // 2. In a SDK (or a custom sysroot) in <sysroot>/usr/include/c++/v1
++    //
++    // The precendence of paths is as listed above, i.e. we take the first path
++    // that exists. Also note that we never include libc++ twice -- we take the
++    // first path that exists and don't send the other paths to CC1 (otherwise
++    // include_next could break).
++
++    // Check for (1)
++    // Get from '<install>/bin' to '<install>/include/c++/v1'.
++    // Note that InstallBin can be relative, so we use '..' instead of
++    // parent_path.
++    llvm::SmallString<128> InstallBin =
++        llvm::StringRef(getDriver().getInstalledDir()); // <install>/bin
++    llvm::sys::path::append(InstallBin, "..", "include", "c++", "v1");
++    if (getVFS().exists(InstallBin)) {
++      addSystemInclude(DriverArgs, CC1Args, InstallBin);
++      return;
++    } else if (DriverArgs.hasArg(options::OPT_v)) {
++      llvm::errs() << "ignoring nonexistent directory \"" << InstallBin
++                   << "\"\n";
+     }
++
++    // Otherwise, check for (2)
++    llvm::SmallString<128> SysrootUsr = Sysroot;
++    llvm::sys::path::append(SysrootUsr, "usr", "include", "c++", "v1");
++    if (getVFS().exists(SysrootUsr)) {
++      addSystemInclude(DriverArgs, CC1Args, SysrootUsr);
++      return;
++    } else if (DriverArgs.hasArg(options::OPT_v)) {
++      llvm::errs() << "ignoring nonexistent directory \"" << SysrootUsr
++                   << "\"\n";
++    }
++
++    // Otherwise, don't add any path.
+     break;
+   }