diff --git a/Formula/llvm@8.rb b/Formula/llvm@8.rb
index 287b794a5554c..722f2f37e9f56 100644
--- a/Formula/llvm@8.rb
+++ b/Formula/llvm@8.rb
@@ -3,6 +3,7 @@ class LlvmAT8 < Formula
   homepage "https://llvm.org/"
   url "https://github.com/llvm/llvm-project/releases/download/llvmorg-8.0.1/llvm-8.0.1.src.tar.xz"
   sha256 "44787a6d02f7140f145e2250d56c9f849334e11f9ae379827510ed72f12b75e7"
+  revision 1
 
   bottle do
     cellar :any
@@ -113,6 +114,11 @@ def install
       -DLIBOMP_INSTALL_ALIASES=OFF
     ]
 
+    if MacOS.version >= :mojave
+      sdk_path = MacOS::CLT.installed? ? "/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk" : MacOS.sdk_path
+      args << "-DDEFAULT_SYSROOT=#{sdk_path}"
+    end
+
     mkdir "build" do
       system "cmake", "-G", "Unix Makefiles", "..", *(std_cmake_args + args)
       system "make"
@@ -144,7 +150,6 @@ def caveats; <<~EOS
       #include <stdlib.h>
       #include <stdio.h>
       #include <omp.h>
-
       int main() {
           #pragma omp parallel num_threads(4)
           {
@@ -172,7 +177,6 @@ def caveats; <<~EOS
 
     (testpath/"test.c").write <<~EOS
       #include <stdio.h>
-
       int main()
       {
         printf("Hello World!\\n");
@@ -182,7 +186,6 @@ def caveats; <<~EOS
 
     (testpath/"test.cpp").write <<~EOS
       #include <iostream>
-
       int main()
       {
         std::cout << "Hello World!" << std::endl;
@@ -190,52 +193,73 @@ def caveats; <<~EOS
       }
     EOS
 
+    # Testing default toolchain and SDK location.
+    system "#{bin}/clang++", "-v",
+           "-std=c++11", "test.cpp", "-o", "test++"
+    assert_includes MachO::Tools.dylibs("test++"), "/usr/lib/libc++.1.dylib"
+    assert_equal "Hello World!", shell_output("./test++").chomp
+    system "#{bin}/clang", "-v", "test.c", "-o", "test"
+    assert_equal "Hello World!", shell_output("./test").chomp
+
     # Testing Command Line Tools
     if MacOS::CLT.installed?
-      libclangclt = Dir["/Library/Developer/CommandLineTools/usr/lib/clang/#{MacOS::CLT.version.to_i}*"].last { |f| File.directory? f }
-
-      system "#{bin}/clang++", "-v", "-nostdinc",
-              "-I/Library/Developer/CommandLineTools/usr/include/c++/v1",
-              "-I#{libclangclt}/include",
-              "-I/usr/include", # need it because /Library/.../usr/include/c++/v1/iosfwd refers to <wchar.h>, which CLT installs to /usr/include
-              "test.cpp", "-o", "testCLT++"
+      toolchain_path = "/Library/Developer/CommandLineTools"
+      sdk_path = "/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk"
+      system "#{bin}/clang++", "-v",
+             "-isysroot", sdk_path,
+             "-isystem", "#{toolchain_path}/usr/include/c++/v1",
+             "-isystem", "#{toolchain_path}/usr/include",
+             "-isystem", "#{sdk_path}/usr/include",
+             "-std=c++11", "test.cpp", "-o", "testCLT++"
       assert_includes MachO::Tools.dylibs("testCLT++"), "/usr/lib/libc++.1.dylib"
       assert_equal "Hello World!", shell_output("./testCLT++").chomp
-
-      system "#{bin}/clang", "-v", "-nostdinc",
-              "-I/usr/include", # this is where CLT installs stdio.h
-              "test.c", "-o", "testCLT"
+      system "#{bin}/clang", "-v", "test.c", "-o", "testCLT"
       assert_equal "Hello World!", shell_output("./testCLT").chomp
     end
 
     # Testing Xcode
     if MacOS::Xcode.installed?
-      libclangxc = Dir["#{MacOS::Xcode.toolchain_path}/usr/lib/clang/#{DevelopmentTools.clang_version}*"].last { |f| File.directory? f }
-
-      system "#{bin}/clang++", "-v", "-nostdinc",
-              "-I#{MacOS::Xcode.toolchain_path}/usr/include/c++/v1",
-              "-I#{libclangxc}/include",
-              "-I#{MacOS.sdk_path}/usr/include",
-              "test.cpp", "-o", "testXC++"
+      system "#{bin}/clang++", "-v",
+             "-isysroot", MacOS.sdk_path,
+             "-isystem", "#{MacOS::Xcode.toolchain_path}/usr/include/c++/v1",
+             "-isystem", "#{MacOS::Xcode.toolchain_path}/usr/include",
+             "-isystem", "#{MacOS.sdk_path}/usr/include",
+             "-std=c++11", "test.cpp", "-o", "testXC++"
       assert_includes MachO::Tools.dylibs("testXC++"), "/usr/lib/libc++.1.dylib"
       assert_equal "Hello World!", shell_output("./testXC++").chomp
-
-      system "#{bin}/clang", "-v", "-nostdinc",
-              "-I#{MacOS.sdk_path}/usr/include",
-              "test.c", "-o", "testXC"
+      system "#{bin}/clang", "-v",
+             "-isysroot", MacOS.sdk_path,
+             "test.c", "-o", "testXC"
       assert_equal "Hello World!", shell_output("./testXC").chomp
     end
 
     # link against installed libc++
     # related to https://github.com/Homebrew/legacy-homebrew/issues/47149
-    system "#{bin}/clang++", "-v", "-nostdinc",
-            "-std=c++11", "-stdlib=libc++",
-            "-I#{MacOS::Xcode.toolchain_path}/usr/include/c++/v1",
-            "-I#{libclangxc}/include",
-            "-I#{MacOS.sdk_path}/usr/include",
-            "-L#{lib}",
-            "-Wl,-rpath,#{lib}", "test.cpp", "-o", "test"
-    assert_includes MachO::Tools.dylibs("test"), "#{opt_lib}/libc++.1.dylib"
-    assert_equal "Hello World!", shell_output("./test").chomp
+    system "#{bin}/clang++", "-v",
+           "-isystem", "#{opt_include}/c++/v1",
+           "-std=c++11", "-stdlib=libc++", "test.cpp", "-o", "testlibc++",
+           "-L#{opt_lib}", "-Wl,-rpath,#{opt_lib}"
+    assert_includes MachO::Tools.dylibs("testlibc++"), "#{opt_lib}/libc++.1.dylib"
+    assert_equal "Hello World!", shell_output("./testlibc++").chomp
+
+    (testpath/"scanbuildtest.cpp").write <<~EOS
+      #include <iostream>
+      int main() {
+        int *i = new int;
+        *i = 1;
+        delete i;
+        std::cout << *i << std::endl;
+        return 0;
+      }
+    EOS
+    assert_includes shell_output("#{bin}/scan-build --use-analyzer #{bin}/clang++ clang++ scanbuildtest.cpp 2>&1"),
+      "warning: Use of memory after it is freed"
+
+    (testpath/"clangformattest.c").write <<~EOS
+      int    main() {
+          printf("Hello world!"); }
+    EOS
+    assert_equal "int main() { printf(\"Hello world!\"); }\n",
+      shell_output("#{bin}/clang-format -style=google clangformattest.c")
   end
 end