1 files changed, 12 insertions, 9 deletions
diff --git a/clang/lib/Driver/ToolChains/Darwin.cpp b/clang/lib/Driver/ToolChains/Darwin.cpp
index 3596be41607..478e1111e18 100644
--- a/clang/lib/Driver/ToolChains/Darwin.cpp
+++ b/clang/lib/Driver/ToolChains/Darwin.cpp
@@ -1805,13 +1805,21 @@ void Darwin::AddDeploymentTarget(DerivedArgList &Args) const {
   }
 }
 
+// Returns the effective header sysroot path to use. This comes either from
+// -isysroot or --sysroot.
+llvm::StringRef DarwinClang::GetHeaderSysroot(const llvm::opt::ArgList &DriverArgs) const {
+  if(DriverArgs.hasArg(options::OPT_isysroot))
+    return DriverArgs.getLastArgValue(options::OPT_isysroot);
+  if (!getDriver().SysRoot.empty())
+    return getDriver().SysRoot;
+  return "/";
+}
+
 void DarwinClang::AddClangSystemIncludeArgs(const llvm::opt::ArgList &DriverArgs,
                                             llvm::opt::ArgStringList &CC1Args) const {
   const Driver &D = getDriver();
 
-  llvm::StringRef Sysroot = "/";
-  if (const Arg *A = DriverArgs.getLastArg(options::OPT_isysroot))
-    Sysroot = A->getValue();
+  llvm::StringRef Sysroot = GetHeaderSysroot(DriverArgs);
 
   bool NoStdInc = DriverArgs.hasArg(options::OPT_nostdinc);
   bool NoStdlibInc = DriverArgs.hasArg(options::OPT_nostdlibinc);
@@ -1897,12 +1905,7 @@ void DarwinClang::AddClangCXXStdlibIncludeArgs(
       DriverArgs.hasArg(options::OPT_nostdincxx))
     return;
 
-  llvm::SmallString<128> Sysroot;
-  if (const Arg *A = DriverArgs.getLastArg(options::OPT_isysroot)) {
-    Sysroot = A->getValue();
-  } else {
-    Sysroot = "/";
-  }
+  llvm::StringRef Sysroot = GetHeaderSysroot(DriverArgs);
 
   switch (GetCXXStdlibType(DriverArgs)) {
   case ToolChain::CST_Libcxx: {