[gcc r14-9339] c++: ICE with noexcept and local specialization [PR114114]

[gcc r14-9339] c++: ICE with noexcept and local specialization [PR114114]

[Marek Polacek]

https://gcc.gnu.org/g:dc6c3bfb59baab28b998e18396c06087b6d9b0ed

commit r14-9339-gdc6c3bfb59baab28b998e18396c06087b6d9b0ed
Author: Marek Polacek <polacek@redhat.com>
Date:   Tue Mar 5 13:33:10 2024 -0500

    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.

Diff:
---
 gcc/cp/pt.cc                            |  6 ++++++
 gcc/testsuite/g++.dg/cpp0x/noexcept84.C | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+)

diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index a6e6c804130..d73f6d93485 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 00000000000..06f33264f77
--- /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>();
+}