[SemaTemplate] Detect instantiation of unparsed exceptions

[davide]

Summary

Full story here: https://llvm.org/bugs/show_bug.cgi?id=24000
Implementing what Richard suggested in the PR.
Cc:ing Dimitry as this caused regression while building some FreeBSD ports.

[dim]

For fixing bug 24000, this patch works. Before the patch:

clang -std=c++11 -c pr24000.cpp
Assertion failed: (EST == EST_Dynamic && "EST case not considered earlier."), function CalledDecl, file /share/dim/src/llvm/trunk/tools/clang/lib/Sema/SemaDeclCXX.cpp, line 208.

After the patch:

clang -std=c++11 -c pr24000.cpp
pr24000.cpp:12:12: error: exception specification is not available until end of class definition
    D<int> d;
           ^
pr24000.cpp:14:10: note: in instantiation of template class 'B<int>' requested here
  B<int> b;
         ^
1 error generated.

This also works correctly for the FreeBSD devel/codeblocks port, which now results in this (expected) error:

In file included from cbthreadpool.cpp:18:
../../src/include/cbthreadpool.h:140:33: error: exception specification is not available until end of class definition
        CountedPtr<wxSemaphore> m_semaphore;
                                ^

[davide]

Thanks for testing Dimitry, I'll try to get this in LLVM and FreeBSD after sign-off from Richard.

[rsmith]

Thanks, LGTM.

cfe/trunk/lib/Sema/SemaExceptionSpec.cpp

if (!isUnresolvedExceptionSpec(SourceFPT->getExceptionSpecType()))
     return SourceFPT;
 
   // Compute or instantiate the exception specification now.
   if (SourceFPT->getExceptionSpecType() == EST_Unevaluated)
     EvaluateImplicitExceptionSpec(Loc, cast<CXXMethodDecl>(SourceDecl));
   else
     InstantiateExceptionSpec(Loc, SourceDecl);
 
-  return SourceDecl->getType()->castAs<FunctionProtoType>();
+  const FunctionProtoType *Proto =
+    SourceDecl->getType()->castAs<FunctionProtoType>();
+  if (Proto->getExceptionSpecType() == clang::EST_Unparsed) {
+    Diag(Loc, diag::err_exception_spec_not_parsed);
+    Proto = nullptr;
+  }
+  return Proto;
 }
 
 void
 Sema::UpdateExceptionSpec(FunctionDecl *FD,
                           const FunctionProtoType::ExceptionSpecInfo &ESI) {
   // If we've fully resolved the exception specification, notify listeners.
   if (!isUnresolvedExceptionSpec(ESI.Type))
     if (auto *Listener = getASTMutationListener())

cfe/trunk/test/SemaTemplate/crash-unparsed-exception.cpp

+// RUN: %clang_cc1 -fsyntax-only -std=c++11 -verify -fcxx-exceptions -fexceptions %s
+
+struct A {
+  virtual ~A();
+};
+template <class>
+struct B {};
+struct C {
+  template <typename>
+  struct D {
+    ~D() throw();
+  };
+  struct E : A {
+    D<int> d; //expected-error{{exception specification is not available until end of class definition}}
+  };
+  B<int> b; //expected-note{{in instantiation of template class 'B<int>' requested here}}
+};