Recommit [driver][macOS] Pick the system version for the

deployment target if the SDK is newer than the system

This commit reverts the revert commit r305891. Now the change from r305678
should be correct because `llvm::sys::getProcessTriple` now returns the correct
macOS version of the system after the LLVM change r307372.

Original commit message:

This commit improves the driver by making sure that it picks the system version
for the deployment target when the version of the macOS SDK is newer than the
system version.

rdar://29449467

Differential Revision: https://reviews.llvm.org/D34175

llvm-svn: 307388

2 files changed, 32 insertions, 1 deletions

diff --git a/clang/lib/Driver/ToolChains/Darwin.cpp b/clang/lib/Driver/ToolChains/Darwin.cpp
index 762d0a16f49..ba1a5ee9559 100644
--- a/clang/lib/Driver/ToolChains/Darwin.cpp
+++ b/clang/lib/Driver/ToolChains/Darwin.cpp
@@ -1118,6 +1118,27 @@ void DarwinClang::AddLinkRuntimeLibArgs(const ArgList &Args,
   }
 }
 
+/// Returns the most appropriate macOS target version for the current process.
+///
+/// If the macOS SDK version is the same or earlier than the system version,
+/// then the SDK version is returned. Otherwise the system version is returned.
+static std::string getSystemOrSDKMacOSVersion(StringRef MacOSSDKVersion) {
+  unsigned Major, Minor, Micro;
+  llvm::Triple SystemTriple(llvm::sys::getProcessTriple());
+  if (!SystemTriple.isMacOSX())
+    return MacOSSDKVersion;
+  SystemTriple.getMacOSXVersion(Major, Minor, Micro);
+  VersionTuple SystemVersion(Major, Minor, Micro);
+  bool HadExtra;
+  if (!Driver::GetReleaseVersion(MacOSSDKVersion, Major, Minor, Micro,
+                                 HadExtra))
+    return MacOSSDKVersion;
+  VersionTuple SDKVersion(Major, Minor, Micro);
+  if (SDKVersion > SystemVersion)
+    return SystemVersion.getAsString();
+  return MacOSSDKVersion;
+}
+
 void Darwin::AddDeploymentTarget(DerivedArgList &Args) const {
   const OptTable &Opts = getDriver().getOpts();
 
@@ -1229,7 +1250,7 @@ void Darwin::AddDeploymentTarget(DerivedArgList &Args) const {
                 SDK.startswith("iPhoneSimulator"))
               iOSTarget = Version;
             else if (SDK.startswith("MacOSX"))
-              OSXTarget = Version;
+              OSXTarget = getSystemOrSDKMacOSVersion(Version);
             else if (SDK.startswith("WatchOS") ||
                      SDK.startswith("WatchSimulator"))
               WatchOSTarget = Version;
diff --git a/clang/test/Driver/darwin-sdk-vs-os-version.c b/clang/test/Driver/darwin-sdk-vs-os-version.c
new file mode 100644
index 00000000000..391f4d5a730
--- /dev/null
+++ b/clang/test/Driver/darwin-sdk-vs-os-version.c
@@ -0,0 +1,10 @@
+// REQUIRES: system-darwin
+
+// Ensure that we never pick a version that's based on the SDK that's newer than
+// the system version:
+// RUN: rm -rf %t/SDKs/MacOSX10.99.99.sdk
+// RUN: mkdir -p %t/SDKs/MacOSX10.99.99.sdk
+// RUN: %clang -target x86_64-apple-darwin -isysroot %t/SDKs/MacOSX10.99.99.sdk %s -### 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-MACOSX-SYSTEM-VERSION %s
+
+// CHECK-MACOSX-SYSTEM-VERSION-NOT: 10.99.99"