diff --git a/clang/include/clang/Basic/DiagnosticGroups.td b/clang/include/clang/Basic/DiagnosticGroups.td
--- a/clang/include/clang/Basic/DiagnosticGroups.td
+++ b/clang/include/clang/Basic/DiagnosticGroups.td
@@ -450,6 +450,7 @@
 def : DiagGroup<"inline">;
 def : DiagGroup<"invalid-pch">;
 def GNULabelsAsValue : DiagGroup<"gnu-label-as-value">;
+def GNULineMarker : DiagGroup<"gnu-line-marker">;
 def LiteralRange : DiagGroup<"literal-range">;
 def LocalTypeTemplateArgs : DiagGroup<"local-type-template-args",
                                       [CXX98CompatLocalTypeTemplateArgs]>;
@@ -1111,7 +1112,7 @@
                             VLAExtension, GNUFlexibleArrayInitializer,
                             GNUFlexibleArrayUnionMember, GNUFoldingConstant,
                             GNUImaginaryConstant, GNUIncludeNext,
-                            GNULabelsAsValue, GNUNullPointerArithmetic,
+                            GNULabelsAsValue, GNULineMarker, GNUNullPointerArithmetic,
                             GNUPointerArith, RedeclaredClassMember,
                             GNURedeclaredEnum, GNUStatementExpression,
                             GNUStaticFloatInit,
diff --git a/clang/include/clang/Basic/DiagnosticLexKinds.td b/clang/include/clang/Basic/DiagnosticLexKinds.td
--- a/clang/include/clang/Basic/DiagnosticLexKinds.td
+++ b/clang/include/clang/Basic/DiagnosticLexKinds.td
@@ -427,6 +427,10 @@
 def ext_pp_opencl_variadic_macros : Extension<
   "variadic macros are a Clang extension in OpenCL">;
 
+def ext_pp_gnu_line_directive : Extension<
+  "this style of line directive is a GNU extension">,
+  InGroup<GNULineMarker>;
+
 def err_pp_invalid_directive : Error<"invalid preprocessing directive">;
 def err_pp_directive_required : Error<
   "%0 must be used within a preprocessing directive">;
diff --git a/clang/lib/Lex/PPDirectives.cpp b/clang/lib/Lex/PPDirectives.cpp
--- a/clang/lib/Lex/PPDirectives.cpp
+++ b/clang/lib/Lex/PPDirectives.cpp
@@ -1431,6 +1431,7 @@
   // If the StrTok is "eod", then it wasn't present.  Otherwise, it must be a
   // string followed by eod.
   if (StrTok.is(tok::eod)) {
+    Diag(StrTok, diag::ext_pp_gnu_line_directive);
     // Treat this like "#line NN", which doesn't change file characteristics.
     FileKind = SourceMgr.getFileCharacteristic(DigitTok.getLocation());
   } else if (StrTok.isNot(tok::string_literal)) {
@@ -1458,6 +1459,9 @@
     // If a filename was present, read any flags that are present.
     if (ReadLineMarkerFlags(IsFileEntry, IsFileExit, FileKind, *this))
       return;
+    if (!SourceMgr.isWrittenInBuiltinFile(DigitTok.getLocation()) &&
+        !SourceMgr.isWrittenInCommandLineFile(DigitTok.getLocation()))
+      Diag(StrTok, diag::ext_pp_gnu_line_directive);
 
     // Exiting to an empty string means pop to the including file, so leave
     // FilenameID as -1 in that case.
diff --git a/clang/test/Preprocessor/line-directive.c b/clang/test/Preprocessor/line-directive-system-headers.c
copy from clang/test/Preprocessor/line-directive.c
copy to clang/test/Preprocessor/line-directive-system-headers.c
--- a/clang/test/Preprocessor/line-directive.c
+++ b/clang/test/Preprocessor/line-directive-system-headers.c
@@ -1,16 +1,11 @@
-// RUN: %clang_cc1 -std=c99 -fsyntax-only -verify -pedantic %s
-// RUN: not %clang_cc1 -E %s 2>&1 | grep 'blonk.c:92:2: error: ABC'
-// RUN: not %clang_cc1 -E %s 2>&1 | grep 'blonk.c:93:2: error: DEF'
-// RUN: not %clang_cc1 -E %s 2>&1 | grep 'line-directive.c:11:2: error: MAIN7'
-// RUN: not %clang_cc1 -E %s 2>&1 | grep 'enter-1:118:2: error: ENTER1'
-// RUN: not %clang_cc1 -E %s 2>&1 | grep 'main:121:2: error: MAIN2'
+// RUN: %clang_cc1 -std=c99 -fsyntax-only -verify -pedantic -Wsystem-headers %s
 
 // expected-error@+1{{cannot pop empty include stack}}
 # 20 "" 2
 
 // a push/pop before any other line control
-# 10 "enter-0" 1
-# 11 "" 2 // pop to main file
+# 10 "enter-0" 1 // expected-warning {{this style of line directive is a GNU extension}}
+# 11 "" 2 // pop to main file: expected-warning {{this style of line directive is a GNU extension}}
 #error MAIN7
 // expected-error@-1{{MAIN7}}
 
@@ -27,13 +22,13 @@
 #define A 42 "foo"
 #line A
 
-# 42
-# 42 "foo"
+# 42 // expected-warning {{this style of line directive is a GNU extension}}
+# 42 "foo" // expected-warning {{this style of line directive is a GNU extension}}
 # 42 "foo" 2 // expected-error {{invalid line marker flag '2': cannot pop empty include stack}}
-# 42 "foo" 1 3  // enter
-# 42 "foo" 2 3  // exit
+# 42 "foo" 1 3  // enter: expected-warning {{this style of line directive is a GNU extension}}
+# 42 "foo" 2 3  // exit: expected-warning {{this style of line directive is a GNU extension}}
 # 42 "foo" 2 3 4 // expected-error {{invalid line marker flag '2': cannot pop empty include stack}}
-# 42 "foo" 3 4
+# 42 "foo" 3 4 // expected-warning {{this style of line directive is a GNU extension}}
 
 # 'a'            // expected-error {{invalid preprocessing directive}}
 # 42 'f'         // expected-error {{invalid filename for line marker directive}}
@@ -54,32 +49,32 @@
 
 // Verify that linemarker diddling of the system header flag works.
 
-# 192 "glomp.h" // not a system header.
+# 192 "glomp.h" // not a system header.: expected-warning {{this style of line directive is a GNU extension}}
 typedef int x;  // expected-note {{previous definition is here}}
 typedef int x;  // expected-warning {{redefinition of typedef 'x' is a C11 feature}}
 
-# 192 "glomp.h" 3 // System header.
-typedef int y;  // ok
-typedef int y;  // ok
+# 192 "glomp.h" 3 // System header.: expected-warning {{this style of line directive is a GNU extension}}
+typedef int y;  // expected-note {{previous definition is here}}
+typedef int y;  // expected-warning {{redefinition of typedef 'y' is a C11 feature}}
 
-typedef int q;  // q is in system header.
+typedef int q;  // q is in system header.: expected-note {{previous definition is here}}
 
 #line 42 "blonk.h"  // doesn't change system headerness.
 
-typedef int z;  // ok
-typedef int z;  // ok
+typedef int z;  // expected-note {{previous definition is here}}
+typedef int z;  // expected-warning {{redefinition of typedef 'z' is a C11 feature}}
 
-# 97     // doesn't change system headerness.
+# 97     // doesn't change system headerness.: expected-warning {{this style of line directive is a GNU extension}}
 
-typedef int z1;  // ok
-typedef int z1;  // ok
+typedef int z1;  // expected-note {{previous definition is here}}
+typedef int z1;  // expected-warning {{redefinition of typedef 'z1' is a C11 feature}}
 
-# 42 "blonk.h"  // DOES change system headerness.
+# 42 "blonk.h"  // DOES change system headerness.: expected-warning {{this style of line directive is a GNU extension}}
 
 typedef int w;  // expected-note {{previous definition is here}}
 typedef int w;  // expected-warning {{redefinition of typedef 'w' is a C11 feature}}
 
-typedef int q;  // original definition in system header, should not diagnose.
+typedef int q;  // expected-warning {{redefinition of typedef 'q' is a C11 feature}}
 
 // This should not produce an "extra tokens at end of #line directive" warning,
 // because #line is allowed to contain expanded tokens.
@@ -97,30 +92,30 @@
 #line 010  // expected-warning {{#line directive interprets number as decimal, not octal}}
 extern int array[__LINE__ == 10 ? 1:-1];
 
-# 020      // expected-warning {{GNU line marker directive interprets number as decimal, not octal}}
+# 020      // expected-warning {{GNU line marker directive interprets number as decimal, not octal}} expected-warning {{this style of line directive is a GNU extension}}
 extern int array_gnuline[__LINE__ == 20 ? 1:-1];
 
 /* PR3917 */
 #line 41
 extern char array2[\
-_\
+    _\
 _LINE__ == 42 ? 1: -1];  /* line marker is location of first _ */
 
-# 51
+# 51 // expected-warning {{this style of line directive is a GNU extension}}
 extern char array2_gnuline[\
-_\
+    _\
 _LINE__ == 52 ? 1: -1];  /* line marker is location of first _ */
 
 // rdar://11550996
 #line 0 "line-directive.c" // expected-warning {{#line directive with zero argument is a GNU extension}}
 undefined t; // expected-error {{unknown type name 'undefined'}}
 
-# 115 "main"
-# 116 "enter-1" 1
-# 117 "enter-2" 1
-# 118 "" 2 // pop to enter-1
+# 115 "main" // expected-warning {{this style of line directive is a GNU extension}}
+# 116 "enter-1" 1 // expected-warning {{this style of line directive is a GNU extension}}
+# 117 "enter-2" 1 // expected-warning {{this style of line directive is a GNU extension}}
+# 118 "" 2 // pop to enter-1: expected-warning {{this style of line directive is a GNU extension}}
 #error ENTER1
 // expected-error@-1{{ENTER1}}
-# 121 "" 2 // pop to "main"
+# 121 "" 2 // pop to "main": expected-warning {{this style of line directive is a GNU extension}}
 #error MAIN2
 // expected-error@-1{{MAIN2}}
diff --git a/clang/test/Preprocessor/line-directive.c b/clang/test/Preprocessor/line-directive.c
--- a/clang/test/Preprocessor/line-directive.c
+++ b/clang/test/Preprocessor/line-directive.c
@@ -9,8 +9,8 @@
 # 20 "" 2
 
 // a push/pop before any other line control
-# 10 "enter-0" 1
-# 11 "" 2 // pop to main file
+# 10 "enter-0" 1 // expected-warning {{this style of line directive is a GNU extension}}
+# 11 "" 2 // pop to main file: expected-warning {{this style of line directive is a GNU extension}}
 #error MAIN7
 // expected-error@-1{{MAIN7}}
 
@@ -27,13 +27,13 @@
 #define A 42 "foo"
 #line A
 
-# 42
-# 42 "foo"
+# 42 // expected-warning {{this style of line directive is a GNU extension}}
+# 42 "foo" // expected-warning {{this style of line directive is a GNU extension}}
 # 42 "foo" 2 // expected-error {{invalid line marker flag '2': cannot pop empty include stack}}
 # 42 "foo" 1 3  // enter
 # 42 "foo" 2 3  // exit
 # 42 "foo" 2 3 4 // expected-error {{invalid line marker flag '2': cannot pop empty include stack}}
-# 42 "foo" 3 4
+# 42 "foo" 3 4 // expected-warning {{this style of line directive is a GNU extension}}
 
 # 'a'            // expected-error {{invalid preprocessing directive}}
 # 42 'f'         // expected-error {{invalid filename for line marker directive}}
@@ -54,7 +54,7 @@
 
 // Verify that linemarker diddling of the system header flag works.
 
-# 192 "glomp.h" // not a system header.
+# 192 "glomp.h" // not a system header.: expected-warning {{this style of line directive is a GNU extension}}
 typedef int x;  // expected-note {{previous definition is here}}
 typedef int x;  // expected-warning {{redefinition of typedef 'x' is a C11 feature}}
 
@@ -97,7 +97,7 @@
 #line 010  // expected-warning {{#line directive interprets number as decimal, not octal}}
 extern int array[__LINE__ == 10 ? 1:-1];
 
-# 020      // expected-warning {{GNU line marker directive interprets number as decimal, not octal}}
+# 020      // expected-warning {{GNU line marker directive interprets number as decimal, not octal}} expected-warning {{this style of line directive is a GNU extension}}
 extern int array_gnuline[__LINE__ == 20 ? 1:-1];
 
 /* PR3917 */
@@ -106,7 +106,7 @@
 _\
 _LINE__ == 42 ? 1: -1];  /* line marker is location of first _ */
 
-# 51
+# 51 // expected-warning {{this style of line directive is a GNU extension}}
 extern char array2_gnuline[\
 _\
 _LINE__ == 52 ? 1: -1];  /* line marker is location of first _ */
@@ -115,12 +115,12 @@
 #line 0 "line-directive.c" // expected-warning {{#line directive with zero argument is a GNU extension}}
 undefined t; // expected-error {{unknown type name 'undefined'}}
 
-# 115 "main"
-# 116 "enter-1" 1
-# 117 "enter-2" 1
-# 118 "" 2 // pop to enter-1
+# 115 "main" // expected-warning {{this style of line directive is a GNU extension}}
+# 116 "enter-1" 1 // expected-warning {{this style of line directive is a GNU extension}}
+# 117 "enter-2" 1 // expected-warning {{this style of line directive is a GNU extension}}
+# 118 "" 2 // pop to enter-1: expected-warning {{this style of line directive is a GNU extension}}
 #error ENTER1
 // expected-error@-1{{ENTER1}}
-# 121 "" 2 // pop to "main"
+# 121 "" 2 // pop to "main": expected-warning {{this style of line directive is a GNU extension}}
 #error MAIN2
 // expected-error@-1{{MAIN2}}
diff --git a/clang/test/SemaCXX/constexpr-string.cpp b/clang/test/SemaCXX/constexpr-string.cpp
--- a/clang/test/SemaCXX/constexpr-string.cpp
+++ b/clang/test/SemaCXX/constexpr-string.cpp
@@ -7,7 +7,7 @@
 // RUN: %clang_cc1 %s -triple armebv7-unknown-linux -std=c++2a -fsyntax-only -verify -pedantic -Wno-vla-extension -fno-signed-char
 // RUN: %clang_cc1 %s -triple armebv7-unknown-linux -std=c++2a -fsyntax-only -verify -pedantic -Wno-vla-extension -fno-wchar -DNO_PREDEFINED_WCHAR_T
 
-# 9 "/usr/include/string.h" 1 3 4
+# 9 "/usr/include/string.h" 1 3 4  // expected-warning {{this style of line directive is a GNU extension}}
 extern "C" {
   typedef decltype(sizeof(int)) size_t;
 
@@ -29,7 +29,7 @@
 }
 # 25 "SemaCXX/constexpr-string.cpp" 2
 
-# 27 "/usr/include/wchar.h" 1 3 4
+# 27 "/usr/include/wchar.h" 1 3 4  // expected-warning {{this style of line directive is a GNU extension}}
 extern "C" {
 #if NO_PREDEFINED_WCHAR_T
   typedef decltype(L'0') wchar_t;