Re: [patch, libstdc++] In debug mode, diagnose empty initializer_list in min/max/minmax

[Eelis van der Weegen <eelis at eelis dot net>]

On 2016-02-23 23:39, Jonathan Wakely wrote:
> On 23/02/16 22:03 +0100, Eelis wrote:
> > The std::min, std::max, and std::minmax overloads that take a std::initializer_list all require that the list is not empty. The attached patch adds debug mode checks for this.
>
> Nice, thanks for the patch.

Hi Jonathan,

Thanks for the review! Updated patch attached.

I couldn't find precedent in the libstdc++ testsuite of tests that test __glibcxx_assert assertions, so I put these under {min,max,minmax}/assert/, analogous to {min,max,minmax}/debug/. Is that ok?

> Otherwise this looks good, but will have to wait until after the GCC 6 release now.

No hurry at all. :)

Cheers,

Eelis

Index: libstdc++-v3/include/debug/formatter.h
===================================================================
--- libstdc++-v3/include/debug/formatter.h	(revision 233636)
+++ libstdc++-v3/include/debug/formatter.h	(working copy)
@@ -127,7 +127,8 @@
     // others
     __msg_equal_allocs,
     __msg_insert_range_from_self,
-    __msg_irreflexive_ordering
+    __msg_irreflexive_ordering,
+    __msg_empty_init_list
   };
 
   class _Error_formatter
Index: libstdc++-v3/src/c++11/debug.cc
===================================================================
--- libstdc++-v3/src/c++11/debug.cc	(revision 233636)
+++ libstdc++-v3/src/c++11/debug.cc	(working copy)
@@ -188,7 +188,8 @@
     "allocators must be equal",
     "attempt to insert with an iterator range [%1.name;, %2.name;) from this"
     " container",
-    "comparison doesn't meet irreflexive requirements, assert(!(a < a))"
+    "comparison doesn't meet irreflexive requirements, assert(!(a < a))",
+    "%1;(): empty initializer_list"
   };
 
   void
Index: libstdc++-v3/include/debug/macros.h
===================================================================
--- libstdc++-v3/include/debug/macros.h	(revision 233636)
+++ libstdc++-v3/include/debug/macros.h	(working copy)
@@ -69,6 +69,12 @@
 		      ._M_iterator(_First, #_First)			\
 		      ._M_iterator(_Last, #_Last))
 
+// Verify that the initializer_list is non-empty.
+#define __glibcxx_check_non_empty_init_list(_List)			\
+_GLIBCXX_DEBUG_VERIFY(_List.size() != 0,				\
+		      _M_message(__gnu_debug::__msg_empty_init_list)	\
+		      ._M_string(__func__))
+
 /** Verify that we can insert into *this with the iterator _Position.
  *  Insertion into a container at a specific position requires that
  *  the iterator be nonsingular, either dereferenceable or past-the-end,
Index: libstdc++-v3/include/debug/debug.h
===================================================================
--- libstdc++-v3/include/debug/debug.h	(revision 233636)
+++ libstdc++-v3/include/debug/debug.h	(working copy)
@@ -87,9 +87,13 @@
 // Verify that the container is nonempty
 # define __glibcxx_requires_nonempty() \
   __glibcxx_assert(! this->empty())
+// Verify that the initializer_list is non-empty.
+# define __glibcxx_requires_non_empty_init_list(_List) \
+  __glibcxx_assert(_List.size() != 0)
 #else
 # define __glibcxx_requires_non_empty_range(_First,_Last)
 # define __glibcxx_requires_nonempty()
+# define __glibcxx_requires_non_empty_init_list(_List)
 #endif
 
 #else
@@ -99,6 +103,8 @@
 # define __glibcxx_requires_cond(_Cond,_Msg) _GLIBCXX_DEBUG_VERIFY(_Cond,_Msg)
 # define __glibcxx_requires_valid_range(_First,_Last)	\
   __glibcxx_check_valid_range(_First,_Last)
+# define __glibcxx_requires_non_empty_init_list(_List)	\
+  __glibcxx_check_non_empty_init_list(_List)
 # define __glibcxx_requires_non_empty_range(_First,_Last)	\
   __glibcxx_check_non_empty_range(_First,_Last)
 # define __glibcxx_requires_sorted(_First,_Last)	\
Index: libstdc++-v3/include/bits/stl_algo.h
===================================================================
--- libstdc++-v3/include/bits/stl_algo.h	(revision 233636)
+++ libstdc++-v3/include/bits/stl_algo.h	(working copy)
@@ -3452,25 +3452,37 @@
     _GLIBCXX14_CONSTEXPR
     inline _Tp
     min(initializer_list<_Tp> __l)
-    { return *std::min_element(__l.begin(), __l.end()); }
+    {
+      __glibcxx_requires_non_empty_init_list(__l);
+      return *std::min_element(__l.begin(), __l.end());
+    }
 
   template<typename _Tp, typename _Compare>
     _GLIBCXX14_CONSTEXPR
     inline _Tp
     min(initializer_list<_Tp> __l, _Compare __comp)
-    { return *std::min_element(__l.begin(), __l.end(), __comp); }
+    {
+      __glibcxx_requires_non_empty_init_list(__l);
+      return *std::min_element(__l.begin(), __l.end(), __comp);
+    }
 
   template<typename _Tp>
     _GLIBCXX14_CONSTEXPR
     inline _Tp
     max(initializer_list<_Tp> __l)
-    { return *std::max_element(__l.begin(), __l.end()); }
+    {
+      __glibcxx_requires_non_empty_init_list(__l);
+      return *std::max_element(__l.begin(), __l.end());
+    }
 
   template<typename _Tp, typename _Compare>
     _GLIBCXX14_CONSTEXPR
     inline _Tp
     max(initializer_list<_Tp> __l, _Compare __comp)
-    { return *std::max_element(__l.begin(), __l.end(), __comp); }
+    {
+      __glibcxx_requires_non_empty_init_list(__l);
+      return *std::max_element(__l.begin(), __l.end(), __comp);
+    }
 
   template<typename _Tp>
     _GLIBCXX14_CONSTEXPR
@@ -3477,6 +3489,7 @@
     inline pair<_Tp, _Tp>
     minmax(initializer_list<_Tp> __l)
     {
+      __glibcxx_requires_non_empty_init_list(__l);
       pair<const _Tp*, const _Tp*> __p =
 	std::minmax_element(__l.begin(), __l.end());
       return std::make_pair(*__p.first, *__p.second);
@@ -3487,6 +3500,7 @@
     inline pair<_Tp, _Tp>
     minmax(initializer_list<_Tp> __l, _Compare __comp)
     {
+      __glibcxx_requires_non_empty_init_list(__l);
       pair<const _Tp*, const _Tp*> __p =
 	std::minmax_element(__l.begin(), __l.end(), __comp);
       return std::make_pair(*__p.first, *__p.second);
Index: libstdc++-v3/testsuite/25_algorithms/max/assert/empty_neg.cc
===================================================================
--- libstdc++-v3/testsuite/25_algorithms/max/assert/empty_neg.cc	(revision 0)
+++ libstdc++-v3/testsuite/25_algorithms/max/assert/empty_neg.cc	(working copy)
@@ -0,0 +1,34 @@
+// Copyright (C) 2016 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-options "-std=gnu++11" }
+// { dg-do run { xfail *-*-* } }
+
+#define _GLIBCXX_ASSERTIONS
+
+#include <algorithm>
+
+void test01()
+{
+  std::max<int>({}); // error: empty initializer_list
+}
+
+int main()
+{
+  test01();
+  return 0;
+}
Index: libstdc++-v3/testsuite/25_algorithms/max/debug/empty_neg.cc
===================================================================
--- libstdc++-v3/testsuite/25_algorithms/max/debug/empty_neg.cc	(revision 0)
+++ libstdc++-v3/testsuite/25_algorithms/max/debug/empty_neg.cc	(working copy)
@@ -0,0 +1,34 @@
+// Copyright (C) 2016 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-options "-std=gnu++11" }
+// { dg-do run { xfail *-*-* } }
+
+#define _GLIBCXX_DEBUG
+
+#include <algorithm>
+
+void test01()
+{
+  std::max<int>({}); // error: empty initializer_list
+}
+
+int main()
+{
+  test01();
+  return 0;
+}
Index: libstdc++-v3/testsuite/25_algorithms/min/assert/empty_neg.cc
===================================================================
--- libstdc++-v3/testsuite/25_algorithms/min/assert/empty_neg.cc	(revision 0)
+++ libstdc++-v3/testsuite/25_algorithms/min/assert/empty_neg.cc	(working copy)
@@ -0,0 +1,34 @@
+// Copyright (C) 2016 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-options "-std=gnu++11" }
+// { dg-do run { xfail *-*-* } }
+
+#define _GLIBCXX_ASSERTIONS
+
+#include <algorithm>
+
+void test01()
+{
+  std::min<int>({}); // error: empty initializer_list
+}
+
+int main()
+{
+  test01();
+  return 0;
+}
Index: libstdc++-v3/testsuite/25_algorithms/min/debug/empty_neg.cc
===================================================================
--- libstdc++-v3/testsuite/25_algorithms/min/debug/empty_neg.cc	(revision 0)
+++ libstdc++-v3/testsuite/25_algorithms/min/debug/empty_neg.cc	(working copy)
@@ -0,0 +1,34 @@
+// Copyright (C) 2016 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-options "-std=gnu++11" }
+// { dg-do run { xfail *-*-* } }
+
+#define _GLIBCXX_DEBUG
+
+#include <algorithm>
+
+void test01()
+{
+  std::min<int>({}); // error: empty initializer_list
+}
+
+int main()
+{
+  test01();
+  return 0;
+}
Index: libstdc++-v3/testsuite/25_algorithms/minmax/assert/empty_neg.cc
===================================================================
--- libstdc++-v3/testsuite/25_algorithms/minmax/assert/empty_neg.cc	(revision 0)
+++ libstdc++-v3/testsuite/25_algorithms/minmax/assert/empty_neg.cc	(working copy)
@@ -0,0 +1,34 @@
+// Copyright (C) 2016 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-options "-std=gnu++11" }
+// { dg-do run { xfail *-*-* } }
+
+#define _GLIBCXX_ASSERTIONS
+
+#include <algorithm>
+
+void test01()
+{
+  std::minmax<int>({}); // error: empty initializer_list
+}
+
+int main()
+{
+  test01();
+  return 0;
+}
Index: libstdc++-v3/testsuite/25_algorithms/minmax/debug/empty_neg.cc
===================================================================
--- libstdc++-v3/testsuite/25_algorithms/minmax/debug/empty_neg.cc	(revision 0)
+++ libstdc++-v3/testsuite/25_algorithms/minmax/debug/empty_neg.cc	(working copy)
@@ -0,0 +1,34 @@
+// Copyright (C) 2016 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-options "-std=gnu++11" }
+// { dg-do run { xfail *-*-* } }
+
+#define _GLIBCXX_DEBUG
+
+#include <algorithm>
+
+void test01()
+{
+  std::minmax<int>({}); // error: empty initializer_list
+}
+
+int main()
+{
+  test01();
+  return 0;
+}