2 files changed, 34 insertions, 2 deletions
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index dfa5647e9df..dead3b69bbd 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -3562,7 +3562,12 @@ bool Sema::MergeFunctionDecl(FunctionDecl *New, NamedDecl *&OldD,
       }
     }
 
-    if (OldQTypeForComparison == NewQType)
+    // If the function types are compatible, merge the declarations. Ignore the
+    // exception specifier because it was already checked above in
+    // CheckEquivalentExceptionSpec, and we don't want follow-on diagnostics
+    // about incompatible types under -fms-compatibility.
+    if (Context.hasSameFunctionTypeIgnoringExceptionSpec(OldQTypeForComparison,
+                                                         NewQType))
       return MergeCompatibleFunctionDecls(New, Old, S, MergeTypeWithOld);
 
     // If the types are imprecise (due to dependent constructs in friends or
diff --git a/clang/test/SemaCXX/ms-exception-spec.cpp b/clang/test/SemaCXX/ms-exception-spec.cpp
index 60bfeba037a..cf460356c97 100644
--- a/clang/test/SemaCXX/ms-exception-spec.cpp
+++ b/clang/test/SemaCXX/ms-exception-spec.cpp
@@ -1,9 +1,36 @@
-// RUN: %clang_cc1 %s -fsyntax-only -verify -fms-compatibility -fexceptions -fcxx-exceptions
+// RUN: %clang_cc1 -std=c++11 %s -fsyntax-only -verify -fms-compatibility -fexceptions -fcxx-exceptions
+// RUN: %clang_cc1 -std=c++17 %s -fsyntax-only -verify -fms-compatibility -fexceptions -fcxx-exceptions
 
+// FIXME: Should -fms-compatibility soften these errors into warnings to match
+// MSVC? In practice, MSVC never implemented dynamic exception specifiers, so
+// there isn't much Windows code in the wild that uses them.
+#if __cplusplus >= 201703L
+// expected-error@+3 {{ISO C++17 does not allow dynamic exception specifications}}
+// expected-note@+2 {{use 'noexcept(false)' instead}}
+#endif
 void f() throw(...) { }
 
 namespace PR28080 {
 struct S;           // expected-note {{forward declaration}}
+#if __cplusplus >= 201703L
+// expected-error@+3 {{ISO C++17 does not allow dynamic exception specifications}}
+// expected-note@+2 {{use 'noexcept(false)' instead}}
+#endif
 void fn() throw(S); // expected-warning {{incomplete type}} expected-note{{previous declaration}}
 void fn() throw();  // expected-warning {{does not match previous declaration}}
 }
+
+template <typename T> struct FooPtr {
+  template <typename U> FooPtr(U *p) : m_pT(nullptr) {}
+
+  template <>
+      // FIXME: It would be better if this note pointed at the primary template
+      // above.
+      // expected-note@+1 {{previous declaration is here}}
+  FooPtr(T *pInterface) throw() // expected-warning {{exception specification in declaration does not match previous declaration}}
+      : m_pT(pInterface) {}
+
+  T *m_pT;
+};
+struct Bar {};
+template struct FooPtr<Bar>; // expected-note {{requested here}}