PR libstdc++/90682 allow set_terminate(0) and set_unexpected(0)

Make these functions restore the default handlers when passed a null
pointer. This is consistent with std::pmr::set_default_resource(0), and
also matches the current behaviour of libc++.

In order to avoid duplicating the preprocessor condition from
eh_term_handler.cc more that into a new eh_term_handler.h header and
define a macro that can be used in both eh_term_handler.cc and
eh_terminate.cc.

	PR libstdc++/90682
	* libsupc++/eh_term_handler.cc: Include eh_term_handler.h to get
	definition of _GLIBCXX_DEFAULT_TERM_HANDLER.
	* libsupc++/eh_term_handler.h: New header defining
	_GLIBCXX_DEFAULT_TERM_HANDLER.
	* libsupc++/eh_terminate.cc: Include eh_term_handler.h.
	(set_terminate): Restore default handler when argument is null.
	(set_unexpected): Likewise.
	* testsuite/18_support/set_terminate.cc: New test.
	* testsuite/18_support/set_unexpected.cc: New test.

From-SVN: r271808

libstdc++-v3/ChangeLog

@@ -1,5 +1,16 @@
 2019-05-31  Jonathan Wakely  <jwakely@redhat.com>
 
+	PR libstdc++/90682
+	* libsupc++/eh_term_handler.cc: Include eh_term_handler.h to get
+	definition of _GLIBCXX_DEFAULT_TERM_HANDLER.
+	* libsupc++/eh_term_handler.h: New header defining
+	_GLIBCXX_DEFAULT_TERM_HANDLER.
+	* libsupc++/eh_terminate.cc: Include eh_term_handler.h.
+	(set_terminate): Restore default handler when argument is null.
+	(set_unexpected): Likewise.
+	* testsuite/18_support/set_terminate.cc: New test.
+	* testsuite/18_support/set_unexpected.cc: New test.
+
 	* include/backward/hashtable.h (size_t, ptrdiff_t)
 	(forward_iterator_tag, input_iterator_tag, _Construct, _Destroy)
 	(distance, vector, pair, __iterator_category): Remove

libstdc++-v3/libsupc++/eh_term_handler.cc

@@ -24,21 +24,8 @@
 
 #include <bits/c++config.h>
 #include "unwind-cxx.h"
+#include "eh_term_handler.h"
 
-/* We default to the talkative, informative handler in a normal hosted
-   library.  This pulls in the demangler, the dyn-string utilities, and
-   elements of the I/O library.  For a low-memory environment, you can return
-   to the earlier "silent death" handler by configuring GCC with
-   --disable-libstdcxx-verbose and rebuilding the library.
-   In a freestanding environment, we default to this latter approach.  */
-
-#if _GLIBCXX_HOSTED && _GLIBCXX_VERBOSE && __cpp_exceptions
 /* The current installed user handler.  */
 std::terminate_handler __cxxabiv1::__terminate_handler =
-	__gnu_cxx::__verbose_terminate_handler;
-#else
-# include <cstdlib>
-/* The current installed user handler.  */
-std::terminate_handler __cxxabiv1::__terminate_handler = std::abort;
-#endif
-
+	_GLIBCXX_DEFAULT_TERM_HANDLER;

libstdc++-v3/libsupc++/eh_term_handler.h

@@ -0,0 +1,39 @@
+// -*- C++ -*- default std::terminate handler
+// Copyright (C) 2002-2019 Free Software Foundation, Inc.
+//
+// This file is part of GCC.
+//
+// GCC is free software; you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation; either version 3, or (at your option)
+// any later version.
+//
+// GCC is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// Under Section 7 of GPL version 3, you are granted additional
+// permissions described in the GCC Runtime Library Exception, version
+// 3.1, as published by the Free Software Foundation.
+
+// You should have received a copy of the GNU General Public License and
+// a copy of the GCC Runtime Library Exception along with this program;
+// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
+// <http://www.gnu.org/licenses/>.
+
+#include <bits/c++config.h>
+
+/* We default to the talkative, informative handler in a normal hosted
+   library.  This pulls in the demangler, the dyn-string utilities, and
+   elements of the I/O library.  For a low-memory environment, you can return
+   to the earlier "silent death" handler by configuring GCC with
+   --disable-libstdcxx-verbose and rebuilding the library.
+   In a freestanding environment, we default to this latter approach.  */
+
+#if _GLIBCXX_HOSTED && _GLIBCXX_VERBOSE && __cpp_exceptions
+# define _GLIBCXX_DEFAULT_TERM_HANDLER __gnu_cxx::__verbose_terminate_handler
+#else
+# include <cstdlib>
+# define _GLIBCXX_DEFAULT_TERM_HANDLER std::abort
+#endif

libstdc++-v3/libsupc++/eh_terminate.cc

@@ -26,6 +26,7 @@
 #include "exception"
 #include <cstdlib>
 #include "unwind-cxx.h"
+#include "eh_term_handler.h"
 #include <bits/exception_defines.h>
 #include <bits/atomic_lockfree_defines.h>
 
@@ -73,6 +74,9 @@ std::unexpected ()
 std::terminate_handler
 std::set_terminate (std::terminate_handler func) throw()
 {
+  if (!func)
+    func = _GLIBCXX_DEFAULT_TERM_HANDLER;
+
   std::terminate_handler old;
 #if ATOMIC_POINTER_LOCK_FREE > 1
   __atomic_exchange (&__terminate_handler, &func, &old, __ATOMIC_ACQ_REL);
@@ -100,6 +104,9 @@ 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);

libstdc++-v3/testsuite/18_support/set_terminate.cc

@@ -0,0 +1,56 @@
+// Copyright (C) 2019 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-do run }
+
+#include <exception>
+#include <testsuite_hooks.h>
+
+void term_handler() { __builtin_abort(); }
+
+void
+test01()
+{
+  const std::terminate_handler orig = std::get_terminate();
+  VERIFY( orig != 0 ); // GNU-specific behaviour
+
+  std::terminate_handler prev = std::set_terminate(term_handler);
+  VERIFY( std::get_terminate() == term_handler );
+  VERIFY( prev == orig );
+
+  prev = std::set_terminate(orig);
+  VERIFY( std::get_terminate() == orig );
+  VERIFY( prev == term_handler );
+}
+
+void
+test02()
+{
+  // PR libstdc++/90682
+  std::set_terminate(0); // Undefined in C++98, unspecified in C++11 and later
+  const std::terminate_handler dfault = std::get_terminate();
+  VERIFY( dfault != 0 ); // GNU-specific behaviour
+  const std::terminate_handler prev = std::set_terminate(0);
+  VERIFY( prev == dfault );
+}
+
+int
+main()
+{
+  test01();
+  test02();
+}

libstdc++-v3/testsuite/18_support/set_unexpected.cc

@@ -0,0 +1,56 @@
+// Copyright (C) 2019 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-do run { target { c++98_only || { c++11_only || c++14_only } } } }
+
+#include <exception>
+#include <testsuite_hooks.h>
+
+void unex_handler() { __builtin_abort(); }
+
+void
+test01()
+{
+  const std::unexpected_handler orig = std::get_unexpected();
+  VERIFY( orig == std::terminate ); // GNU-specific behaviour
+
+  std::unexpected_handler prev = std::set_unexpected(unex_handler);
+  VERIFY( std::get_unexpected() == unex_handler );
+  VERIFY( prev == orig );
+
+  prev = std::set_unexpected(orig);
+  VERIFY( std::get_unexpected() == orig );
+  VERIFY( prev == unex_handler );
+}
+
+void
+test02()
+{
+  // PR libstdc++/90682
+  std::set_unexpected(0); // Undefined in C++98, unspecified in C++11 and C++14
+  const std::unexpected_handler dfault = std::get_unexpected();
+  VERIFY( dfault == std::terminate ); // GNU-specific behaviour
+  const std::unexpected_handler prev = std::set_unexpected(0);
+  VERIFY( prev == dfault );
+}
+
+int
+main()
+{
+  test01();
+  test02();
+}