From 3bf116c1a4f88d6e3f3fd0887453dea3569e0823 Mon Sep 17 00:00:00 2001
From: Alex Lorenz <arphaman@gmail.com>
Date: Fri, 26 Apr 2019 22:40:47 +0000
Subject: [PATCH] [driver][macOS] Link libarclite from the default toolchain
 when clang is running in a toolchain outside of xcode

'libarclite' usually lives in the same toolchain as 'clang'. However, the
Swift open source toolchains for macOS distribute Clang without 'libarclite'.
In that case, to allow the linker to find 'libarclite', we point to the
'libarclite' that should be in the XcodeDefault toolchain instead. The
path to the toolchain is inferred from the SDK path if it's specified.

https://bugs.swift.org/browse/SR-9972
rdar://49947573

llvm-svn: 359353
---
 clang/lib/Driver/ToolChains/Darwin.cpp             | 31 +++++++++++++++++++++-
 .../test/Driver/arclite-link-external-toolchain.c  |  8 ++++++
 2 files changed, 38 insertions(+), 1 deletion(-)
 create mode 100644 clang/test/Driver/arclite-link-external-toolchain.c

diff --git a/clang/lib/Driver/ToolChains/Darwin.cpp b/clang/lib/Driver/ToolChains/Darwin.cpp
index 20ef6a8..4e24a81 100644
--- a/clang/lib/Driver/ToolChains/Darwin.cpp
+++ b/clang/lib/Driver/ToolChains/Darwin.cpp
@@ -893,6 +893,18 @@ void DarwinClang::addClangWarningOptions(ArgStringList &CC1Args) const {
   }
 }
 
+/// Take a path that speculatively points into Xcode and return the
+/// `XCODE/Contents/Developer` path if it is an Xcode path, or an empty path
+/// otherwise.
+static StringRef getXcodeDeveloperPath(StringRef PathIntoXcode) {
+  static constexpr llvm::StringLiteral XcodeAppSuffix(
+      ".app/Contents/Developer");
+  size_t Index = PathIntoXcode.find(XcodeAppSuffix);
+  if (Index == StringRef::npos)
+    return "";
+  return PathIntoXcode.take_front(Index + XcodeAppSuffix.size());
+}
+
 void DarwinClang::AddLinkARCArgs(const ArgList &Args,
                                  ArgStringList &CmdArgs) const {
   // Avoid linking compatibility stubs on i386 mac.
@@ -905,10 +917,27 @@ void DarwinClang::AddLinkARCArgs(const ArgList &Args,
       runtime.hasSubscripting())
     return;
 
-  CmdArgs.push_back("-force_load");
   SmallString<128> P(getDriver().ClangExecutable);
   llvm::sys::path::remove_filename(P); // 'clang'
   llvm::sys::path::remove_filename(P); // 'bin'
+
+  // 'libarclite' usually lives in the same toolchain as 'clang'. However, the
+  // Swift open source toolchains for macOS distribute Clang without libarclite.
+  // In that case, to allow the linker to find 'libarclite', we point to the
+  // 'libarclite' in the XcodeDefault toolchain instead.
+  if (getXcodeDeveloperPath(P).empty()) {
+    if (const Arg *A = Args.getLastArg(options::OPT_isysroot)) {
+      // Try to infer the path to 'libarclite' in the toolchain from the
+      // specified SDK path.
+      StringRef XcodePathForSDK = getXcodeDeveloperPath(A->getValue());
+      if (!XcodePathForSDK.empty()) {
+        P = XcodePathForSDK;
+        llvm::sys::path::append(P, "Toolchains/XcodeDefault.xctoolchain/usr");
+      }
+    }
+  }
+
+  CmdArgs.push_back("-force_load");
   llvm::sys::path::append(P, "lib", "arc", "libarclite_");
   // Mash in the platform.
   if (isTargetWatchOSSimulator())
diff --git a/clang/test/Driver/arclite-link-external-toolchain.c b/clang/test/Driver/arclite-link-external-toolchain.c
new file mode 100644
index 0000000..2e6f8c1
--- /dev/null
+++ b/clang/test/Driver/arclite-link-external-toolchain.c
@@ -0,0 +1,8 @@
+// RUN: rm -rf %t.tmpdir
+// RUN: mkdir -p %t.tmpdir/Xcode.app/Contents/Developers/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk
+// RUN: %clang -### -target x86_64-apple-macos10.10 -fobjc-link-runtime -lfoo \
+// RUN:   -isysroot %t.tmpdir/Xcode.app/Contents/Developers/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk \
+// RUN:   %s 2>&1 | FileCheck %s
+
+// CHECK: -lfoo
+// CHECK: .tmpdir/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/arc/libarclite_macosx.a
-- 
2.7.4