6 files changed, 28 insertions, 6 deletions

diff --git a/clang/lib/Serialization/ASTReaderDecl.cpp b/clang/lib/Serialization/ASTReaderDecl.cpp
index 2a01d853c7c..9a382c1659d 100644
--- a/clang/lib/Serialization/ASTReaderDecl.cpp
+++ b/clang/lib/Serialization/ASTReaderDecl.cpp
@@ -2833,14 +2833,23 @@ void ASTDeclReader::attachPreviousDeclImpl(ASTReader &Reader,
 
   // If this declaration has an unresolved exception specification but the
   // previous declaration had a resolved one, resolve the exception
-  // specification now.
+  // specification now. If this declaration has a resolved exception
+  // specification but the previous declarations did not, apply our exception
+  // specification to all prior ones now.
   auto *FPT = FD->getType()->getAs<FunctionProtoType>();
   auto *PrevFPT = PrevFD->getType()->getAs<FunctionProtoType>();
-  if (FPT && PrevFPT &&
-      isUnresolvedExceptionSpec(FPT->getExceptionSpecType()) &&
-      !isUnresolvedExceptionSpec(PrevFPT->getExceptionSpecType())) {
-    Reader.Context.adjustExceptionSpec(
-        FD, PrevFPT->getExtProtoInfo().ExceptionSpec);
+  if (FPT && PrevFPT) {
+    bool WasUnresolved = isUnresolvedExceptionSpec(FPT->getExceptionSpecType());
+    bool IsUnresolved = isUnresolvedExceptionSpec(PrevFPT->getExceptionSpecType());
+    if (WasUnresolved && !IsUnresolved) {
+      Reader.Context.adjustExceptionSpec(
+          FD, PrevFPT->getExtProtoInfo().ExceptionSpec);
+    } else if (!WasUnresolved && IsUnresolved) {
+      FunctionProtoType::ExtProtoInfo EPI = FPT->getExtProtoInfo();
+      for (FunctionDecl *PrevFDToUpdate = PrevFD; PrevFDToUpdate;
+           PrevFDToUpdate = PrevFDToUpdate->getPreviousDecl())
+         Reader.Context.adjustExceptionSpec(PrevFDToUpdate, EPI.ExceptionSpec);
+    }
   }
 }
 }
diff --git a/clang/test/Modules/Inputs/PR21687/a.h b/clang/test/Modules/Inputs/PR21687/a.h
new file mode 100644
index 00000000000..023606eb35a
--- /dev/null
+++ b/clang/test/Modules/Inputs/PR21687/a.h
@@ -0,0 +1 @@
+struct X { X(); virtual ~X(); };
diff --git a/clang/test/Modules/Inputs/PR21687/b.h b/clang/test/Modules/Inputs/PR21687/b.h
new file mode 100644
index 00000000000..7085b1f6739
--- /dev/null
+++ b/clang/test/Modules/Inputs/PR21687/b.h
@@ -0,0 +1,2 @@
+#include "a.h"
+X *n = new X;
diff --git a/clang/test/Modules/Inputs/PR21687/c.h b/clang/test/Modules/Inputs/PR21687/c.h
new file mode 100644
index 00000000000..5c5d555a3f0
--- /dev/null
+++ b/clang/test/Modules/Inputs/PR21687/c.h
@@ -0,0 +1,4 @@
+#include "a.h"
+inline void f() { X x, y(x); }
+#include "b.h"
+X x, y(x);
diff --git a/clang/test/Modules/Inputs/PR21687/module.modulemap b/clang/test/Modules/Inputs/PR21687/module.modulemap
new file mode 100644
index 00000000000..77e0a89e39a
--- /dev/null
+++ b/clang/test/Modules/Inputs/PR21687/module.modulemap
@@ -0,0 +1,3 @@
+module a { header "a.h" export * }
+module b { header "b.h" export * }
+module c { header "c.h" export * }
diff --git a/clang/test/Modules/pr21687.cpp b/clang/test/Modules/pr21687.cpp
new file mode 100644
index 00000000000..ad67489541d
--- /dev/null
+++ b/clang/test/Modules/pr21687.cpp
@@ -0,0 +1,3 @@
+// RUN: rm -rf %t
+// RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t -I%S/Inputs/PR21687 -emit-llvm-only %s
+#include "c.h"