[PATCH] D116256: [-fms-extensions] Make some exception specification warnings/errors compatible with what cl.exe does

[Amy Huang via Phabricator via cfe-commits]

This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Closed by commit rG28d2977ff236: [-fms-extensions] Make some exception 
specification warnings/errors compatible… (authored by akhuang).

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Files:
  clang/include/clang/Basic/DiagnosticSemaKinds.td
  clang/lib/Sema/SemaExceptionSpec.cpp
  clang/test/SemaCXX/MicrosoftCompatibility.cpp


Index: clang/test/SemaCXX/MicrosoftCompatibility.cpp
===
--- clang/test/SemaCXX/MicrosoftCompatibility.cpp
+++ clang/test/SemaCXX/MicrosoftCompatibility.cpp
@@ -2,6 +2,8 @@
 // RUN: %clang_cc1 %s -triple i686-pc-win32 -fsyntax-only -std=c++11 
-Wmicrosoft -verify -fms-compatibility -fexceptions -fcxx-exceptions 
-fms-compatibility-version=19.27
 // RUN: %clang_cc1 %s -triple i686-pc-win32 -fsyntax-only -std=c++11 
-Wmicrosoft -verify -fms-compatibility -fexceptions -fcxx-exceptions 
-fms-compatibility-version=19.00
 // RUN: %clang_cc1 %s -triple i686-pc-win32 -fsyntax-only -std=c++11 
-Wmicrosoft -verify -fms-compatibility -fexceptions -fcxx-exceptions 
-fms-compatibility-version=18.00
+// RUN: %clang_cc1 %s -triple i686-pc-win32 -fsyntax-only -std=c++17 
-Wmicrosoft -verify -fms-compatibility -fexceptions -fcxx-exceptions
+
 
 #if defined(_HAS_CHAR16_T_LANGUAGE_SUPPORT) && _HAS_CHAR16_T_LANGUAGE_SUPPORT
 char16_t x;
@@ -350,6 +352,7 @@
 void foo(); // expected-note {{previous declaration}}
 void foo() throw(); // expected-warning {{exception specification in 
declaration does not match previous declaration}}
 
+#if __cplusplus < 201703L
 void r6() throw(...); // expected-note {{previous declaration}}
 void r6() throw(int); // expected-warning {{exception specification in 
declaration does not match previous declaration}}
 
@@ -362,6 +365,7 @@
   virtual void f2() throw(...);
   virtual void f3();
 };
+#endif
 
 class A {
   virtual ~A() throw();
@@ -377,14 +381,14 @@
 #endif
 };
 
-}
+void f4() throw(); // expected-note {{previous declaration is here}}
+void f4() {}   // expected-warning {{'f4' is missing exception 
specification 'throw()'}}
 
-namespace PR25265 {
-struct S {
-  int fn() throw(); // expected-note {{previous declaration is here}}
-};
+__declspec(nothrow) void f5();
+void f5() {}
 
-int S::fn() { return 0; } // expected-warning {{is missing exception 
specification}}
+void f6() noexcept; // expected-note {{previous declaration is here}}
+void f6() {}// expected-error {{'f6' is missing exception 
specification 'noexcept'}}
 }
 
 namespace PR43265 {
Index: clang/lib/Sema/SemaExceptionSpec.cpp
===
--- clang/lib/Sema/SemaExceptionSpec.cpp
+++ clang/lib/Sema/SemaExceptionSpec.cpp
@@ -391,9 +391,8 @@
 NewProto->getExtProtoInfo().withExceptionSpec(ESI)));
   }
 
-  if (getLangOpts().MSVCCompat && ESI.Type != EST_DependentNoexcept) {
-// Allow missing exception specifications in redeclarations as an 
extension.
-DiagID = diag::ext_ms_missing_exception_specification;
+  if (getLangOpts().MSVCCompat && isDynamicExceptionSpec(ESI.Type)) {
+DiagID = diag::ext_missing_exception_specification;
 ReturnValueOnError = false;
   } else if (New->isReplaceableGlobalAllocationFunction() &&
  ESI.Type != EST_DependentNoexcept) {
@@ -402,6 +401,10 @@
 DiagID = diag::ext_missing_exception_specification;
 ReturnValueOnError = false;
   } else if (ESI.Type == EST_NoThrow) {
+// Don't emit any warning for missing 'nothrow' in MSVC.
+if (getLangOpts().MSVCCompat) {
+  return false;
+}
 // Allow missing attribute 'nothrow' in redeclarations, since this is a 
very
 // common omission.
 DiagID = diag::ext_missing_exception_specification;
Index: clang/include/clang/Basic/DiagnosticSemaKinds.td
===
--- clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -1695,9 +1695,6 @@
 def ext_missing_exception_specification : ExtWarn<
   err_missing_exception_specification.Text>,
   InGroup>;
-def ext_ms_missing_exception_specification : ExtWarn<
-  err_missing_exception_specification.Text>,
-  InGroup;
 def err_noexcept_needs_constant_expression : Error<
   "argument to noexcept specifier must be a constant expression">;
 def err_exception_spec_not_parsed : Error<


Index: clang/test/SemaCXX/MicrosoftCompatibility.cpp
===
--- clang/test/SemaCXX/MicrosoftCompatibility.cpp
+++ clang/test/SemaCXX/MicrosoftCompatibility.cpp
@@ -2,6 +2,8 @@
 // RUN: %clang_cc1 %s -triple i686-pc-win32 -fsyntax-only -std=c++11 -Wmicrosoft -verify -fms-compatibility -fexceptions -fcxx-exceptions 

[PATCH] D116256: [-fms-extensions] Make some exception specification warnings/errors compatible with what cl.exe does

[Nico Weber via Phabricator via cfe-commits]

thakis accepted this revision.
thakis added a comment.
This revision is now accepted and ready to land.

Thanks!


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[PATCH] D116256: [-fms-extensions] Make some exception specification warnings/errors compatible with what cl.exe does

[Amy Huang via Phabricator via cfe-commits]

akhuang updated this revision to Diff 397930.
akhuang marked an inline comment as done.
akhuang added a comment.

Add std=c++17 to the test.


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Files:
  clang/include/clang/Basic/DiagnosticSemaKinds.td
  clang/lib/Sema/SemaExceptionSpec.cpp
  clang/test/SemaCXX/MicrosoftCompatibility.cpp


Index: clang/test/SemaCXX/MicrosoftCompatibility.cpp
===
--- clang/test/SemaCXX/MicrosoftCompatibility.cpp
+++ clang/test/SemaCXX/MicrosoftCompatibility.cpp
@@ -2,6 +2,8 @@
 // RUN: %clang_cc1 %s -triple i686-pc-win32 -fsyntax-only -std=c++11 
-Wmicrosoft -verify -fms-compatibility -fexceptions -fcxx-exceptions 
-fms-compatibility-version=19.27
 // RUN: %clang_cc1 %s -triple i686-pc-win32 -fsyntax-only -std=c++11 
-Wmicrosoft -verify -fms-compatibility -fexceptions -fcxx-exceptions 
-fms-compatibility-version=19.00
 // RUN: %clang_cc1 %s -triple i686-pc-win32 -fsyntax-only -std=c++11 
-Wmicrosoft -verify -fms-compatibility -fexceptions -fcxx-exceptions 
-fms-compatibility-version=18.00
+// RUN: %clang_cc1 %s -triple i686-pc-win32 -fsyntax-only -std=c++17 
-Wmicrosoft -verify -fms-compatibility -fexceptions -fcxx-exceptions
+
 
 #if defined(_HAS_CHAR16_T_LANGUAGE_SUPPORT) && _HAS_CHAR16_T_LANGUAGE_SUPPORT
 char16_t x;
@@ -350,6 +352,7 @@
 void foo(); // expected-note {{previous declaration}}
 void foo() throw(); // expected-warning {{exception specification in 
declaration does not match previous declaration}}
 
+#if __cplusplus < 201703L
 void r6() throw(...); // expected-note {{previous declaration}}
 void r6() throw(int); // expected-warning {{exception specification in 
declaration does not match previous declaration}}
 
@@ -362,6 +365,7 @@
   virtual void f2() throw(...);
   virtual void f3();
 };
+#endif
 
 class A {
   virtual ~A() throw();
@@ -377,14 +381,14 @@
 #endif
 };
 
-}
+void f4() throw(); // expected-note {{previous declaration is here}}
+void f4() {}   // expected-warning {{'f4' is missing exception 
specification 'throw()'}}
 
-namespace PR25265 {
-struct S {
-  int fn() throw(); // expected-note {{previous declaration is here}}
-};
+__declspec(nothrow) void f5();
+void f5() {}
 
-int S::fn() { return 0; } // expected-warning {{is missing exception 
specification}}
+void f6() noexcept; // expected-note {{previous declaration is here}}
+void f6() {}// expected-error {{'f6' is missing exception 
specification 'noexcept'}}
 }
 
 namespace PR43265 {
Index: clang/lib/Sema/SemaExceptionSpec.cpp
===
--- clang/lib/Sema/SemaExceptionSpec.cpp
+++ clang/lib/Sema/SemaExceptionSpec.cpp
@@ -391,9 +391,8 @@
 NewProto->getExtProtoInfo().withExceptionSpec(ESI)));
   }
 
-  if (getLangOpts().MSVCCompat && ESI.Type != EST_DependentNoexcept) {
-// Allow missing exception specifications in redeclarations as an 
extension.
-DiagID = diag::ext_ms_missing_exception_specification;
+  if (getLangOpts().MSVCCompat && isDynamicExceptionSpec(ESI.Type)) {
+DiagID = diag::ext_missing_exception_specification;
 ReturnValueOnError = false;
   } else if (New->isReplaceableGlobalAllocationFunction() &&
  ESI.Type != EST_DependentNoexcept) {
@@ -402,6 +401,10 @@
 DiagID = diag::ext_missing_exception_specification;
 ReturnValueOnError = false;
   } else if (ESI.Type == EST_NoThrow) {
+// Don't emit any warning for missing 'nothrow' in MSVC.
+if (getLangOpts().MSVCCompat) {
+  return false;
+}
 // Allow missing attribute 'nothrow' in redeclarations, since this is a 
very
 // common omission.
 DiagID = diag::ext_missing_exception_specification;
Index: clang/include/clang/Basic/DiagnosticSemaKinds.td
===
--- clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -1695,9 +1695,6 @@
 def ext_missing_exception_specification : ExtWarn<
   err_missing_exception_specification.Text>,
   InGroup>;
-def ext_ms_missing_exception_specification : ExtWarn<
-  err_missing_exception_specification.Text>,
-  InGroup;
 def err_noexcept_needs_constant_expression : Error<
   "argument to noexcept specifier must be a constant expression">;
 def err_exception_spec_not_parsed : Error<


Index: clang/test/SemaCXX/MicrosoftCompatibility.cpp
===
--- clang/test/SemaCXX/MicrosoftCompatibility.cpp
+++ clang/test/SemaCXX/MicrosoftCompatibility.cpp
@@ -2,6 +2,8 @@
 // RUN: %clang_cc1 %s -triple i686-pc-win32 -fsyntax-only -std=c++11 -Wmicrosoft -verify -fms-compatibility -fexceptions -fcxx-exceptions -fms-compatibility-version=19.27
 // RUN: %clang_cc1 %s -triple i686-pc-win32 -fsyntax-only -std=c++11 -Wmicrosoft -verify -fms-compatibility -fexceptions 

[PATCH] D116256: [-fms-extensions] Make some exception specification warnings/errors compatible with what cl.exe does

[Nico Weber via Phabricator via cfe-commits]

thakis added inline comments.



Comment at: clang/test/SemaCXX/MicrosoftCompatibility.cpp:4
 // RUN: %clang_cc1 %s -triple i686-pc-win32 -fsyntax-only -std=c++11 
-Wmicrosoft -verify -fms-compatibility -fexceptions -fcxx-exceptions 
-fms-compatibility-version=19.00
 // RUN: %clang_cc1 %s -triple i686-pc-win32 -fsyntax-only -std=c++11 
-Wmicrosoft -verify -fms-compatibility -fexceptions -fcxx-exceptions 
-fms-compatibility-version=18.00
 

Could you add a run line with `-std=c++17`?


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[PATCH] D116256: [-fms-extensions] Make some exception specification warnings/errors compatible with what cl.exe does

[Amy Huang via Phabricator via cfe-commits]

akhuang added a comment.

In D116256#3215801 , @thakis wrote:

> Thanks for the patch! This looks roughly right to me.
>
> Maybe the list of ESTs that are allowed to be mismatched should be opt-in 
> instead of opt-out? (i.e. instead of checking for "not EST_BasicNoexcept /  
> EST_DependentNoexcept", check for EST_NoThrow (I think?) Not sure which way 
> is better.
>
> (Looks like the old code was added for https://llvm.org/PR25265)
>
> Could you check that we still emit the warning on line 5 in 
> https://godbolt.org/z/bxfx8jsjd ? The test is mostly from 
> https://docs.microsoft.com/en-us/cpp/build/reference/zc-noexcepttypes?view=msvc-170
>  -- it feels like we might want to have different behavior in c++17 (and 
> later) and c++14 (and earlier) for some of the diags, possibly. Looks like 
> MSVC also has an error on line 15 by default (with /std:c++17, it seems to 
> accept it with /std:c++14), while we only warn.
>
> (I'm a bit surprised the `noexcept` bit doesn't make it into the mangled name 
> in the ms abi, but we're consistent with msvc about this so that's all good.)

It did not still emit the warning but I've changed it now. I'm not sure why 
https://llvm.org/PR25265 added a new warning 
(ext_ms_missing_exception_specification) instead of just using 
ext_missing_exception_specification; I guess I'll get rid of it anyway.


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[PATCH] D116256: [-fms-extensions] Make some exception specification warnings/errors compatible with what cl.exe does

[Amy Huang via Phabricator via cfe-commits]

akhuang updated this revision to Diff 397760.
akhuang marked an inline comment as done.
akhuang added a comment.

Fix warning behavior


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Files:
  clang/include/clang/Basic/DiagnosticSemaKinds.td
  clang/lib/Sema/SemaExceptionSpec.cpp
  clang/test/SemaCXX/MicrosoftCompatibility.cpp


Index: clang/test/SemaCXX/MicrosoftCompatibility.cpp
===
--- clang/test/SemaCXX/MicrosoftCompatibility.cpp
+++ clang/test/SemaCXX/MicrosoftCompatibility.cpp
@@ -377,14 +377,14 @@
 #endif
 };
 
-}
+void f4() throw(); // expected-note {{previous declaration is here}}
+void f4() {}   // expected-warning {{'f4' is missing exception 
specification 'throw()'}}
 
-namespace PR25265 {
-struct S {
-  int fn() throw(); // expected-note {{previous declaration is here}}
-};
+__declspec(nothrow) void f5();
+void f5() {}
 
-int S::fn() { return 0; } // expected-warning {{is missing exception 
specification}}
+void f6() noexcept; // expected-note {{previous declaration is here}}
+void f6() {}// expected-error {{'f6' is missing exception 
specification 'noexcept'}}
 }
 
 namespace PR43265 {
Index: clang/lib/Sema/SemaExceptionSpec.cpp
===
--- clang/lib/Sema/SemaExceptionSpec.cpp
+++ clang/lib/Sema/SemaExceptionSpec.cpp
@@ -391,9 +391,8 @@
 NewProto->getExtProtoInfo().withExceptionSpec(ESI)));
   }
 
-  if (getLangOpts().MSVCCompat && ESI.Type != EST_DependentNoexcept) {
-// Allow missing exception specifications in redeclarations as an 
extension.
-DiagID = diag::ext_ms_missing_exception_specification;
+  if (getLangOpts().MSVCCompat && isDynamicExceptionSpec(ESI.Type)) {
+DiagID = diag::ext_missing_exception_specification;
 ReturnValueOnError = false;
   } else if (New->isReplaceableGlobalAllocationFunction() &&
  ESI.Type != EST_DependentNoexcept) {
@@ -402,6 +401,10 @@
 DiagID = diag::ext_missing_exception_specification;
 ReturnValueOnError = false;
   } else if (ESI.Type == EST_NoThrow) {
+// Don't emit any warning for missing 'nothrow' in MSVC.
+if (getLangOpts().MSVCCompat) {
+  return false;
+}
 // Allow missing attribute 'nothrow' in redeclarations, since this is a 
very
 // common omission.
 DiagID = diag::ext_missing_exception_specification;
Index: clang/include/clang/Basic/DiagnosticSemaKinds.td
===
--- clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -1695,9 +1695,6 @@
 def ext_missing_exception_specification : ExtWarn<
   err_missing_exception_specification.Text>,
   InGroup>;
-def ext_ms_missing_exception_specification : ExtWarn<
-  err_missing_exception_specification.Text>,
-  InGroup;
 def err_noexcept_needs_constant_expression : Error<
   "argument to noexcept specifier must be a constant expression">;
 def err_exception_spec_not_parsed : Error<


Index: clang/test/SemaCXX/MicrosoftCompatibility.cpp
===
--- clang/test/SemaCXX/MicrosoftCompatibility.cpp
+++ clang/test/SemaCXX/MicrosoftCompatibility.cpp
@@ -377,14 +377,14 @@
 #endif
 };
 
-}
+void f4() throw(); // expected-note {{previous declaration is here}}
+void f4() {}   // expected-warning {{'f4' is missing exception specification 'throw()'}}
 
-namespace PR25265 {
-struct S {
-  int fn() throw(); // expected-note {{previous declaration is here}}
-};
+__declspec(nothrow) void f5();
+void f5() {}
 
-int S::fn() { return 0; } // expected-warning {{is missing exception specification}}
+void f6() noexcept; // expected-note {{previous declaration is here}}
+void f6() {}// expected-error {{'f6' is missing exception specification 'noexcept'}}
 }
 
 namespace PR43265 {
Index: clang/lib/Sema/SemaExceptionSpec.cpp
===
--- clang/lib/Sema/SemaExceptionSpec.cpp
+++ clang/lib/Sema/SemaExceptionSpec.cpp
@@ -391,9 +391,8 @@
 NewProto->getExtProtoInfo().withExceptionSpec(ESI)));
   }
 
-  if (getLangOpts().MSVCCompat && ESI.Type != EST_DependentNoexcept) {
-// Allow missing exception specifications in redeclarations as an extension.
-DiagID = diag::ext_ms_missing_exception_specification;
+  if (getLangOpts().MSVCCompat && isDynamicExceptionSpec(ESI.Type)) {
+DiagID = diag::ext_missing_exception_specification;
 ReturnValueOnError = false;
   } else if (New->isReplaceableGlobalAllocationFunction() &&
  ESI.Type != EST_DependentNoexcept) {
@@ -402,6 +401,10 @@
 DiagID = diag::ext_missing_exception_specification;
 ReturnValueOnError = false;
   } else if (ESI.Type == EST_NoThrow) {
+// Don't emit any warning for missing 'nothrow' in MSVC.
+if 

[PATCH] D116256: [-fms-extensions] Make some exception specification warnings/errors compatible with what cl.exe does

[Nico Weber via Phabricator via cfe-commits]

thakis added a comment.

Thanks for the patch! This looks roughly right to me.

Maybe the list of ESTs that are allowed to be mismatched should be opt-in 
instead of opt-out? (i.e. instead of checking for "not EST_BasicNoexcept /  
EST_DependentNoexcept", check for EST_NoThrow (I think?) Not sure which way is 
better.

(Looks like the old code was added for https://llvm.org/PR25265)

Could you check that we still emit the warning on line 5 in 
https://godbolt.org/z/bxfx8jsjd ? The test is mostly from 
https://docs.microsoft.com/en-us/cpp/build/reference/zc-noexcepttypes?view=msvc-170
 -- it feels like we might want to have different behavior in c++17 (and later) 
and c++14 (and earlier) for some of the diags, possibly. Looks like MSVC also 
has an error on line 15 by default (with /std:c++17, it seems to accept it with 
/std:c++14), while we only warn.

(I'm a bit surprised the `noexcept` bit doesn't make it into the mangled name 
in the ms abi, but we're consistent with msvc about this so that's all good.)




Comment at: clang/lib/Sema/SemaExceptionSpec.cpp:399
+return false;
   } else if (New->isReplaceableGlobalAllocationFunction() &&
  ESI.Type != EST_DependentNoexcept) {

nit: LLVM style says "no else after return", so this should become a regular 
`if` now.


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[PATCH] D116256: [-fms-extensions] Make some exception specification warnings/errors compatible with what cl.exe does

[Amy Huang via Phabricator via cfe-commits]

akhuang created this revision.
akhuang added reviewers: hans, thakis.
akhuang requested review of this revision.
Herald added a project: clang.
Herald added a subscriber: cfe-commits.

Make clang-cl error when a function definition is missing 'noexcept',
and succeed without warnings when missing '__declspec(nothrow)' or 'throw'.

Fixes pr52860


Repository:
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Files:
  clang/include/clang/Basic/DiagnosticSemaKinds.td
  clang/lib/Sema/SemaExceptionSpec.cpp
  clang/test/SemaCXX/MicrosoftCompatibility.cpp


Index: clang/test/SemaCXX/MicrosoftCompatibility.cpp
===
--- clang/test/SemaCXX/MicrosoftCompatibility.cpp
+++ clang/test/SemaCXX/MicrosoftCompatibility.cpp
@@ -377,14 +377,14 @@
 #endif
 };
 
-}
+void f4() throw();
+void f4() {}
 
-namespace PR25265 {
-struct S {
-  int fn() throw(); // expected-note {{previous declaration is here}}
-};
+__declspec(nothrow) void f5();
+void f5() {}
 
-int S::fn() { return 0; } // expected-warning {{is missing exception 
specification}}
+void f6() noexcept; // expected-note {{previous declaration is here}}
+void f6() {}// expected-error {{'f6' is missing exception 
specification 'noexcept'}}
 }
 
 namespace PR43265 {
Index: clang/lib/Sema/SemaExceptionSpec.cpp
===
--- clang/lib/Sema/SemaExceptionSpec.cpp
+++ clang/lib/Sema/SemaExceptionSpec.cpp
@@ -391,10 +391,11 @@
 NewProto->getExtProtoInfo().withExceptionSpec(ESI)));
   }
 
-  if (getLangOpts().MSVCCompat && ESI.Type != EST_DependentNoexcept) {
-// Allow missing exception specifications in redeclarations as an 
extension.
-DiagID = diag::ext_ms_missing_exception_specification;
-ReturnValueOnError = false;
+  if (getLangOpts().MSVCCompat &&
+  !(ESI.Type == EST_DependentNoexcept || ESI.Type == EST_BasicNoexcept)) {
+// Allow missing exception specifications in redeclarations as an extension
+// without a warning.
+return false;
   } else if (New->isReplaceableGlobalAllocationFunction() &&
  ESI.Type != EST_DependentNoexcept) {
 // Allow missing exception specifications in redeclarations as an 
extension,
Index: clang/include/clang/Basic/DiagnosticSemaKinds.td
===
--- clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -1695,9 +1695,6 @@
 def ext_missing_exception_specification : ExtWarn<
   err_missing_exception_specification.Text>,
   InGroup>;
-def ext_ms_missing_exception_specification : ExtWarn<
-  err_missing_exception_specification.Text>,
-  InGroup;
 def err_noexcept_needs_constant_expression : Error<
   "argument to noexcept specifier must be a constant expression">;
 def err_exception_spec_not_parsed : Error<


Index: clang/test/SemaCXX/MicrosoftCompatibility.cpp
===
--- clang/test/SemaCXX/MicrosoftCompatibility.cpp
+++ clang/test/SemaCXX/MicrosoftCompatibility.cpp
@@ -377,14 +377,14 @@
 #endif
 };
 
-}
+void f4() throw();
+void f4() {}
 
-namespace PR25265 {
-struct S {
-  int fn() throw(); // expected-note {{previous declaration is here}}
-};
+__declspec(nothrow) void f5();
+void f5() {}
 
-int S::fn() { return 0; } // expected-warning {{is missing exception specification}}
+void f6() noexcept; // expected-note {{previous declaration is here}}
+void f6() {}// expected-error {{'f6' is missing exception specification 'noexcept'}}
 }
 
 namespace PR43265 {
Index: clang/lib/Sema/SemaExceptionSpec.cpp
===
--- clang/lib/Sema/SemaExceptionSpec.cpp
+++ clang/lib/Sema/SemaExceptionSpec.cpp
@@ -391,10 +391,11 @@
 NewProto->getExtProtoInfo().withExceptionSpec(ESI)));
   }
 
-  if (getLangOpts().MSVCCompat && ESI.Type != EST_DependentNoexcept) {
-// Allow missing exception specifications in redeclarations as an extension.
-DiagID = diag::ext_ms_missing_exception_specification;
-ReturnValueOnError = false;
+  if (getLangOpts().MSVCCompat &&
+  !(ESI.Type == EST_DependentNoexcept || ESI.Type == EST_BasicNoexcept)) {
+// Allow missing exception specifications in redeclarations as an extension
+// without a warning.
+return false;
   } else if (New->isReplaceableGlobalAllocationFunction() &&
  ESI.Type != EST_DependentNoexcept) {
 // Allow missing exception specifications in redeclarations as an extension,
Index: clang/include/clang/Basic/DiagnosticSemaKinds.td
===
--- clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -1695,9 +1695,6 @@
 def ext_missing_exception_specification : ExtWarn<
   err_missing_exception_specification.Text>,
   InGroup>;
-def