c++: ICE with noexcept and local specialization [PR114114]

Here we ICE because we call register_local_specialization while
local_specializations is null, so

  local_specializations->put ();

crashes on null this.  It's null since maybe_instantiate_noexcept calls
push_to_top_level which creates a new scope.  Normally, I would have
guessed that we need a new local_specialization_stack.  But here we're
dealing with an operand of a noexcept, which is an unevaluated operand,
and those aren't registered in the hash map.  maybe_instantiate_noexcept
wasn't signalling that it's substituting an unevaluated operand though.

	PR c++/114114

gcc/cp/ChangeLog:

	* pt.cc (maybe_instantiate_noexcept): Save/restore
	cp_unevaluated_operand, c_inhibit_evaluation_warnings, and
	cp_noexcept_operand around the tsubst_expr call.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp0x/noexcept84.C: New test.

2 files changed, 38 insertions, 0 deletions

diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index a6e6c80..d73f6d9 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -26879,10 +26879,16 @@ maybe_instantiate_noexcept (tree fn, tsubst_flags_t complain)
 	  if (orig_fn)
 	    ++processing_template_decl;
 
+	  ++cp_unevaluated_operand;
+	  ++c_inhibit_evaluation_warnings;
+	  ++cp_noexcept_operand;
 	  /* Do deferred instantiation of the noexcept-specifier.  */
 	  noex = tsubst_expr (DEFERRED_NOEXCEPT_PATTERN (noex),
 			      DEFERRED_NOEXCEPT_ARGS (noex),
 			      tf_warning_or_error, fn);
+	  --cp_unevaluated_operand;
+	  --c_inhibit_evaluation_warnings;
+	  --cp_noexcept_operand;
 
 	  /* Build up the noexcept-specification.  */
 	  spec = build_noexcept_spec (noex, tf_warning_or_error);
diff --git a/gcc/testsuite/g++.dg/cpp0x/noexcept84.C b/gcc/testsuite/g++.dg/cpp0x/noexcept84.C
new file mode 100644
index 0000000..06f3326
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/noexcept84.C
@@ -0,0 +1,32 @@
+// PR c++/114114
+// { dg-do compile { target c++11 } }
+
+template<bool B>
+constexpr void
+test ()
+{
+  constexpr bool is_yes = B;
+  struct S {
+    constexpr S() noexcept(is_yes) { }
+  };
+  S s;
+}
+
+constexpr bool foo() { return true; }
+
+template<typename T>
+constexpr void
+test2 ()
+{
+  constexpr T (*pfn)() = &foo;
+  struct S {
+    constexpr S() noexcept(pfn()) { }
+  };
+  S s;
+}
+
+int main()
+{
+  test<true>();
+  test2<bool>();
+}