Re: [PATCH] PR libstdc++/71579 assert that type traits are not misused with an incomplete type

[Jonathan Wakely <jwakely at redhat dot com>]

On 31/05/19 11:35 +0100, Jonathan Wakely wrote:
> On 31/05/19 08:58 +0300, Antony Polukhin wrote:
> > On Thu, May 30, 2019, 19:38 Jonathan Wakely <jwakely@redhat.com> wrote:
> > <...>
> >
> > > I've attached a relative diff, to be applied on top of yours, with my
> > > suggested tweaks. Do you see any issues with it?
> > >
> > > (If you're happy with those tweaks I can go ahead and apply this,
> > > there's no need for an updated patch from you).
> >
> > Looks good. Please apply!
>
> Here's what I've tested and committed to trunk.
>
> I decided to add a more detailed changelog too.

I'm removing some of these assertions again, because they are either
reundant or wrong.

Tested x86_64-linux, committed to trunk.


commit 6ffe4cf371688563be1680ffb75cc1160540cf2e
Author: redi <redi@138bc75d-0d04-0410-961f-82ee72b054a4>
Date:   Thu Jun 6 12:13:47 2019 +0000

    Remove redundant static assertions in [meta.unary.prop] traits
    
    The type property predicates that are implemented by a compiler builtin
    already do the right checks in the compiler. The checks for complete
    type or unbounded arrays were wrong for these types anyway.
    
            * include/std/type_traits (is_empty, is_polymorphic, is_final)
            (is_abstract, is_aggregate): Remove static_assert.
            * testsuite/20_util/is_abstract/incomplete_neg.cc: Check for error
            from builtin only.
            * testsuite/20_util/is_aggregate/incomplete_neg.cc: Likewise. Add
            missing -std=gnu++17 option.
            * testsuite/20_util/is_empty/incomplete_neg.cc: New test.
            * testsuite/20_util/is_final/incomplete_neg.cc: New test.
            * testsuite/20_util/is_polymorphic/incomplete_neg.cc: Check for error
            from builtin only.
    
    git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@272000 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
index 78a113af415..e53d3c8d535 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -746,19 +746,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   template<typename _Tp>
     struct is_empty
     : public integral_constant<bool, __is_empty(_Tp)>
-    {
-      static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
-	"template argument must be a complete class or an unbounded array");
-    };
+    { };
 
   /// is_polymorphic
   template<typename _Tp>
     struct is_polymorphic
     : public integral_constant<bool, __is_polymorphic(_Tp)>
-    {
-      static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
-	"template argument must be a complete class or an unbounded array");
-    };
+    { };
 
 #if __cplusplus >= 201402L
 #define __cpp_lib_is_final 201402L
@@ -766,20 +760,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   template<typename _Tp>
     struct is_final
     : public integral_constant<bool, __is_final(_Tp)>
-    {
-      static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
-	"template argument must be a complete class or an unbounded array");
-    };
+    { };
 #endif
 
   /// is_abstract
   template<typename _Tp>
     struct is_abstract
     : public integral_constant<bool, __is_abstract(_Tp)>
-    {
-      static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
-	"template argument must be a complete class or an unbounded array");
-    };
+    { };
 
   template<typename _Tp,
 	   bool = is_arithmetic<_Tp>::value>
@@ -3174,10 +3162,7 @@ template <typename _From, typename _To>
   template<typename _Tp>
     struct is_aggregate
     : bool_constant<__is_aggregate(remove_cv_t<_Tp>)>
-    {
-      static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
-	"template argument must be a complete class or an unbounded array");
-    };
+    { };
 
   /// is_aggregate_v
   template<typename _Tp>
diff --git a/libstdc++-v3/testsuite/20_util/is_abstract/incomplete_neg.cc b/libstdc++-v3/testsuite/20_util/is_abstract/incomplete_neg.cc
index 94f4ecd6000..a2a73d01a06 100644
--- a/libstdc++-v3/testsuite/20_util/is_abstract/incomplete_neg.cc
+++ b/libstdc++-v3/testsuite/20_util/is_abstract/incomplete_neg.cc
@@ -1,7 +1,5 @@
 // { dg-do compile { target c++11 } }
-// { dg-prune-output "invalid use of incomplete type" }
-// { dg-prune-output "must be a complete" }
-//
+
 // Copyright (C) 2019 Free Software Foundation, Inc.
 //
 // This file is part of the GNU ISO C++ Library.  This library is free
@@ -19,6 +17,9 @@
 // with this library; see the file COPYING3.  If not see
 // <http://www.gnu.org/licenses/>.
 
+// Expect the compiler builtin to do the completeness check.
+// { dg-error "incomplete type" "" { target *-*-* } 0 }
+
 #include <type_traits>
 
 class X;
diff --git a/libstdc++-v3/testsuite/20_util/is_aggregate/incomplete_neg.cc b/libstdc++-v3/testsuite/20_util/is_aggregate/incomplete_neg.cc
index 8a3dd551cbb..eff3f64c476 100644
--- a/libstdc++-v3/testsuite/20_util/is_aggregate/incomplete_neg.cc
+++ b/libstdc++-v3/testsuite/20_util/is_aggregate/incomplete_neg.cc
@@ -1,5 +1,6 @@
+// { dg-options "-std=gnu++17" }
 // { dg-do compile { target c++17 } }
-//
+
 // Copyright (C) 2019 Free Software Foundation, Inc.
 //
 // This file is part of the GNU ISO C++ Library.  This library is free
@@ -17,7 +18,8 @@
 // with this library; see the file COPYING3.  If not see
 // <http://www.gnu.org/licenses/>.
 
-// { dg-error "must be a complete class" "" { target *-*-* } 0 }
+// Expect the compiler builtin to do the completeness check.
+// { dg-error "incomplete type" "" { target *-*-* } 0 }
 
 #include <type_traits>
 
diff --git a/libstdc++-v3/testsuite/20_util/is_empty/incomplete_neg.cc b/libstdc++-v3/testsuite/20_util/is_empty/incomplete_neg.cc
new file mode 100644
index 00000000000..3bacefbab7e
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/is_empty/incomplete_neg.cc
@@ -0,0 +1,30 @@
+// { dg-do compile { target c++11 } }
+
+// 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/>.
+
+// Expect the compiler builtin to do the completeness check.
+// { dg-error "incomplete type" "" { target *-*-* } 0 }
+
+#include <type_traits>
+
+class X;
+
+void test01()
+{
+  std::is_empty<X>();		// { dg-error "required from here" }
+}
diff --git a/libstdc++-v3/testsuite/20_util/is_final/incomplete_neg.cc b/libstdc++-v3/testsuite/20_util/is_final/incomplete_neg.cc
new file mode 100644
index 00000000000..0727c090a83
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/is_final/incomplete_neg.cc
@@ -0,0 +1,30 @@
+// { dg-do compile { target c++14 } }
+
+// 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/>.
+
+// Expect the compiler builtin to do the completeness check.
+// { dg-error "incomplete type" "" { target *-*-* } 0 }
+
+#include <type_traits>
+
+class X;
+
+void test01()
+{
+  std::is_final<X>();		// { dg-error "required from here" }
+}
diff --git a/libstdc++-v3/testsuite/20_util/is_polymorphic/incomplete_neg.cc b/libstdc++-v3/testsuite/20_util/is_polymorphic/incomplete_neg.cc
index 8cd1b402a41..618c4fa7a9a 100644
--- a/libstdc++-v3/testsuite/20_util/is_polymorphic/incomplete_neg.cc
+++ b/libstdc++-v3/testsuite/20_util/is_polymorphic/incomplete_neg.cc
@@ -1,7 +1,5 @@
 // { dg-do compile { target c++11 } }
-// { dg-prune-output "invalid use of incomplete type" }
-// { dg-prune-output "must be a complete" }
-//
+
 // Copyright (C) 2019 Free Software Foundation, Inc.
 //
 // This file is part of the GNU ISO C++ Library.  This library is free
@@ -19,6 +17,9 @@
 // with this library; see the file COPYING3.  If not see
 // <http://www.gnu.org/licenses/>.
 
+// Expect the compiler builtin to do the completeness check.
+// { dg-error "incomplete type" "" { target *-*-* } 0 }
+
 #include <type_traits>
 
 class X;