[Bug libstdc++/90682] std::terminate() will happily call a null terminate handler

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90682

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2019-05-30
     Ever confirmed|0                           |1

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Jonathan Wakely from comment #0)
> I think we should treat a null handler as equivalent to abort, e.g.
> 
> --- a/libstdc++-v3/libsupc++/eh_terminate.cc
> +++ b/libstdc++-v3/libsupc++/eh_terminate.cc
> @@ -44,7 +44,8 @@ __cxxabiv1::__terminate (std::terminate_handler handler)
> throw ()
>  {
>    __try 
>      {
> -      handler ();
> +      if (handler)
> +       handler ();
>        std::abort ();
>      } 
>    __catch(...)

Another option would be to make set_terminate(nullptr) consistent with
pmr::set_default_resource(nullptr), i.e. restore the default:

--- a/libstdc++-v3/libsupc++/eh_terminate.cc
+++ b/libstdc++-v3/libsupc++/eh_terminate.cc
@@ -73,6 +73,14 @@ std::unexpected ()
 std::terminate_handler
 std::set_terminate (std::terminate_handler func) throw()
 {
+#if _GLIBCXX_HOSTED && _GLIBCXX_VERBOSE && __cpp_exceptions
+  if (!func)
+    func = __gnu_cxx::__verbose_terminate_handler;
+#else
+  if (!func)
+    func = std::abort;
+#endif
+
   std::terminate_handler old;
 #if ATOMIC_POINTER_LOCK_FREE > 1
   __atomic_exchange (&__terminate_handler, &func, &old, __ATOMIC_ACQ_REL);


This would mean that std::get_terminate() never returns a null pointer, and we
don't need to check for null in std::terminate(). This is what libc++ does.

Whatever we do for terminate/set_terminate we should also do for
unexpected/set_unexpected, e.g.

@@ -100,6 +108,9 @@ std::get_terminate () noexcept
 std::unexpected_handler
 std::set_unexpected (std::unexpected_handler func) throw()
 {
+  if (!func)
+    func = std::terminate;
+
   std::unexpected_handler old;
 #if ATOMIC_POINTER_LOCK_FREE > 1
   __atomic_exchange (&__unexpected_handler, &func, &old, __ATOMIC_ACQ_REL);