Index: test/clang-tidy/llvm-include-order.cpp
===================================================================
--- test/clang-tidy/llvm-include-order.cpp
+++ test/clang-tidy/llvm-include-order.cpp
@@ -1,4 +1,4 @@
-// RUN: %check_clang_tidy %s llvm-include-order %t -- -- -isystem %S/Inputs/Headers
+// RUN: %check_clang_tidy %s llvm-include-order %t -- -- -isystem %S/Inputs/Headers -nostdinc
 
 // CHECK-MESSAGES: [[@LINE+2]]:1: warning: #includes are not sorted properly
 #include "j.h"
Index: test/clang-tidy/misc-move-constructor-init.cpp
===================================================================
--- test/clang-tidy/misc-move-constructor-init.cpp
+++ test/clang-tidy/misc-move-constructor-init.cpp
@@ -1,7 +1,7 @@
 // RUN: %check_clang_tidy %s misc-move-constructor-init,modernize-pass-by-value %t -- \
 // RUN: -config='{CheckOptions: \
 // RUN:  [{key: modernize-pass-by-value.ValuesOnly, value: 1}]}' \
-// RUN: -- -std=c++11 -isystem %S/Inputs/Headers
+// RUN: -- -std=c++11 -isystem %S/Inputs/Headers -nostdinc
 
 #include <s.h>
 
Index: test/clang-tidy/misc-unconventional-assign-operator.cpp
===================================================================
--- test/clang-tidy/misc-unconventional-assign-operator.cpp
+++ test/clang-tidy/misc-unconventional-assign-operator.cpp
@@ -1,4 +1,4 @@
-// RUN: %check_clang_tidy %s misc-unconventional-assign-operator %t -- -- -std=c++11 -isystem %S/Inputs/Headers -fno-delayed-template-parsing
+// RUN: %check_clang_tidy %s misc-unconventional-assign-operator %t -- -- -std=c++11 -isystem %S/Inputs/Headers -fno-delayed-template-parsing -nostdinc
 
 namespace std {
 template <typename T>
Index: test/clang-tidy/misc-unused-using-decls.cpp
===================================================================
--- test/clang-tidy/misc-unused-using-decls.cpp
+++ test/clang-tidy/misc-unused-using-decls.cpp
@@ -1,4 +1,4 @@
-// RUN: %check_clang_tidy %s misc-unused-using-decls %t -- -- -fno-delayed-template-parsing -isystem %S/Inputs/
+// RUN: %check_clang_tidy %s misc-unused-using-decls %t -- -- -fno-delayed-template-parsing -isystem %S/Inputs/ -nostdinc
 
 
 // ----- Definitions -----
Index: test/clang-tidy/modernize-deprecated-headers-cxx03.cpp
===================================================================
--- test/clang-tidy/modernize-deprecated-headers-cxx03.cpp
+++ test/clang-tidy/modernize-deprecated-headers-cxx03.cpp
@@ -1,4 +1,4 @@
-// RUN: %check_clang_tidy %s modernize-deprecated-headers %t -- -extra-arg-before=-isystem%S/Inputs/modernize-deprecated-headers -- -std=c++03 -v
+// RUN: %check_clang_tidy %s modernize-deprecated-headers %t -- -extra-arg-before=-isystem%S/Inputs/modernize-deprecated-headers -- -std=c++03 -v -nostdinc
 
 #include <assert.h>
 // CHECK-MESSAGES: :[[@LINE-1]]:10: warning: inclusion of deprecated C++ header 'assert.h'; consider using 'cassert' instead [modernize-deprecated-headers]
Index: test/clang-tidy/modernize-deprecated-headers-cxx11.cpp
===================================================================
--- test/clang-tidy/modernize-deprecated-headers-cxx11.cpp
+++ test/clang-tidy/modernize-deprecated-headers-cxx11.cpp
@@ -1,4 +1,4 @@
-// RUN: %check_clang_tidy %s modernize-deprecated-headers %t -- -extra-arg-before=-isystem%S/Inputs/modernize-deprecated-headers -- -std=c++11 -v
+// RUN: %check_clang_tidy %s modernize-deprecated-headers %t -- -extra-arg-before=-isystem%S/Inputs/modernize-deprecated-headers -- -std=c++11 -v -nostdinc
 
 #include <assert.h>
 // CHECK-MESSAGES: :[[@LINE-1]]:10: warning: inclusion of deprecated C++ header 'assert.h'; consider using 'cassert' instead [modernize-deprecated-headers]
Index: test/clang-tidy/modernize-pass-by-value-macro-header.cpp
===================================================================
--- test/clang-tidy/modernize-pass-by-value-macro-header.cpp
+++ test/clang-tidy/modernize-pass-by-value-macro-header.cpp
@@ -1,4 +1,4 @@
-// RUN: %check_clang_tidy %s modernize-pass-by-value %t -- -- -std=c++11 -isystem %S/Inputs/Headers
+// RUN: %check_clang_tidy %s modernize-pass-by-value %t -- -- -std=c++11 -isystem %S/Inputs/Headers -nostdinc
 
 // CHECK-FIXES: #include <utility>
 
Index: test/clang-tidy/readability-identifier-naming.cpp
===================================================================
--- test/clang-tidy/readability-identifier-naming.cpp
+++ test/clang-tidy/readability-identifier-naming.cpp
@@ -70,7 +70,7 @@
 // RUN:     {key: readability-identifier-naming.IgnoreFailedSplit, value: 0} \
 // RUN:   ]}' -- -std=c++11 -fno-delayed-template-parsing \
 // RUN:   -I%S/Inputs/readability-identifier-naming \
-// RUN:   -isystem %S/Inputs/readability-identifier-naming/system
+// RUN:   -isystem %S/Inputs/readability-identifier-naming/system -nostdinc
 
 // clang-format off
 
Index: test/pp-trace/pp-trace-conditional.cpp
===================================================================
--- test/pp-trace/pp-trace-conditional.cpp
+++ test/pp-trace/pp-trace-conditional.cpp
@@ -1,4 +1,4 @@
-// RUN: pp-trace -ignore FileChanged %s -undef -target x86_64 -std=c++11 | FileCheck --strict-whitespace %s
+// RUN: pp-trace -ignore FileChanged %s -ffreestanding -undef -target x86_64 -std=c++11 | FileCheck --strict-whitespace %s
 
 #if 1
 #endif
Index: test/pp-trace/pp-trace-ident.cpp
===================================================================
--- test/pp-trace/pp-trace-ident.cpp
+++ test/pp-trace/pp-trace-ident.cpp
@@ -1,4 +1,4 @@
-// RUN: pp-trace -ignore FileChanged,MacroDefined %s -undef -target x86_64 -std=c++11 | FileCheck --strict-whitespace %s
+// RUN: pp-trace -ignore FileChanged,MacroDefined %s -undef -ffreestanding -target x86_64 -std=c++11 | FileCheck --strict-whitespace %s
 
 #ident "$Id$"
 
Index: test/pp-trace/pp-trace-include.cpp
===================================================================
--- test/pp-trace/pp-trace-include.cpp
+++ test/pp-trace/pp-trace-include.cpp
@@ -1,4 +1,4 @@
-// RUN: pp-trace %s -undef -target x86_64 -std=c++11 | FileCheck --strict-whitespace %s
+// RUN: pp-trace %s -undef -ffreestanding -target x86_64 -std=c++11 | FileCheck --strict-whitespace %s
 
 #include "Inputs/Level1A.h"
 #include "Inputs/Level1B.h"
Index: test/pp-trace/pp-trace-macro.cpp
===================================================================
--- test/pp-trace/pp-trace-macro.cpp
+++ test/pp-trace/pp-trace-macro.cpp
@@ -1,4 +1,4 @@
-// RUN: pp-trace -ignore FileChanged %s -undef -target x86_64 -std=c++11 | FileCheck --strict-whitespace %s
+// RUN: pp-trace -ignore FileChanged %s -undef -ffreestanding -target x86_64 -std=c++11 | FileCheck --strict-whitespace %s
 
 #define MACRO 1
 int i = MACRO;
Index: test/pp-trace/pp-trace-modules.cpp
===================================================================
--- test/pp-trace/pp-trace-modules.cpp
+++ test/pp-trace/pp-trace-modules.cpp
@@ -1,5 +1,5 @@
 // RUN: rm -rf %t
-// RUN: pp-trace -ignore FileChanged,MacroDefined %s -x objective-c++ -undef -target x86_64 -std=c++11 -fmodules -fcxx-modules -fmodules-cache-path=%t -I%S -I%S/Input | FileCheck --strict-whitespace %s
+// RUN: pp-trace -ignore FileChanged,MacroDefined %s -x objective-c++ -undef -ffreestanding -target x86_64 -std=c++11 -fmodules -fcxx-modules -fmodules-cache-path=%t -I%S -I%S/Input | FileCheck --strict-whitespace %s
 
 // CHECK: ---
 
Index: test/pp-trace/pp-trace-pragma-general.cpp
===================================================================
--- test/pp-trace/pp-trace-pragma-general.cpp
+++ test/pp-trace/pp-trace-pragma-general.cpp
@@ -1,4 +1,4 @@
-// RUN: pp-trace -ignore FileChanged,MacroDefined %s | FileCheck --strict-whitespace %s
+// RUN: pp-trace -ignore FileChanged,MacroDefined %s -ffreestanding | FileCheck --strict-whitespace %s
 
 #pragma clang diagnostic push
 #pragma clang diagnostic pop
Index: test/pp-trace/pp-trace-pragma-ms.cpp
===================================================================
--- test/pp-trace/pp-trace-pragma-ms.cpp
+++ test/pp-trace/pp-trace-pragma-ms.cpp
@@ -1,4 +1,4 @@
-// RUN: pp-trace -ignore FileChanged,MacroDefined %s -target x86_64 -fms-extensions -w | FileCheck --strict-whitespace %s
+// RUN: pp-trace -ignore FileChanged,MacroDefined %s -target x86_64 -fms-extensions -w -ffreestanding | FileCheck --strict-whitespace %s
 
 #pragma comment(compiler, "compiler comment")
 #pragma comment(exestr, "exestr comment")
Index: test/pp-trace/pp-trace-pragma-opencl.cpp
===================================================================
--- test/pp-trace/pp-trace-pragma-opencl.cpp
+++ test/pp-trace/pp-trace-pragma-opencl.cpp
@@ -1,4 +1,4 @@
-// RUN: pp-trace -ignore FileChanged,MacroDefined %s -x cl | FileCheck --strict-whitespace %s
+// RUN: pp-trace -ignore FileChanged,MacroDefined %s -ffreestanding -x cl | FileCheck --strict-whitespace %s
 
 #pragma OPENCL EXTENSION all : disable
 #pragma OPENCL EXTENSION cl_khr_int64_base_atomics : disable