Re: [PATCH] Help compiler detect invalid code

[Jonathan Wakely <jwakely at redhat dot com>]

On 19/09/19 22:27 +0200, François Dumont wrote:
> Hi
>
>     I start working on making recently added constexpr tests to work 
> in Debug mode.

The attached patch seems to be necessary for that, right?


commit c47326afadb0c330c19b872d5969d2f656499d0a
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Thu Sep 26 15:44:04 2019 +0100

    Make debug mode checks work in C++20 constexpr algorithms
    
            * include/debug/formatter.h (__check_singular): Add
            _GLIBCXX20_CONSTEXPR.
            * include/debug/functions.h (__check_singular_aux, __check_singular)
            (__check_valid_range, __foreign_iterator_aux4, __foreign_iterator_aux3)
            (__foreign_iterator_aux2, __foreign_iterator_aux, __foreign_iterator)
            (__check_sorted_aux, __check_sorted, __check_sorted_set_aux)
            __check_sorted_set, __check_partitioned_lower)
            (__check_partitioned_upper, _Irreflexive_checker::_S_is_valid)
            (_Irreflexive_checker::_S_is_valid_pred, __is_reflexive)
            (__is_reflexive_pred): Likewise.
            * include/debug/helper_functions.h (__get_distance, __valid_range_aux)
            (__valid_range, __can_advance, __base, __unsafe): Likewise.
            * include/debug/safe_iterator.h (__valid_range, __can_advance)
            (__base, __unsafe): Likewise.
            * include/debug/safe_local_iterator.h (__valid_range, __can_advance)
            (__unsafe): Likewise.

diff --git a/libstdc++-v3/include/debug/formatter.h b/libstdc++-v3/include/debug/formatter.h
index 220379994c0..6f17ab4627c 100644
--- a/libstdc++-v3/include/debug/formatter.h
+++ b/libstdc++-v3/include/debug/formatter.h
@@ -72,7 +72,7 @@ namespace __gnu_debug
   using std::type_info;
 
   template<typename _Iterator>
-    bool __check_singular(const _Iterator&);
+    _GLIBCXX20_CONSTEXPR bool __check_singular(const _Iterator&);
 
   class _Safe_sequence_base;
 
diff --git a/libstdc++-v3/include/debug/functions.h b/libstdc++-v3/include/debug/functions.h
index f87838692c6..bbfbe15fefa 100644
--- a/libstdc++-v3/include/debug/functions.h
+++ b/libstdc++-v3/include/debug/functions.h
@@ -50,19 +50,19 @@ namespace __gnu_debug
     struct _Is_contiguous_sequence : std::__false_type { };
 
   // An arbitrary iterator pointer is not singular.
-  inline bool
+  _GLIBCXX20_CONSTEXPR inline bool
   __check_singular_aux(const void*) { return false; }
 
   // We may have an iterator that derives from _Safe_iterator_base but isn't
   // a _Safe_iterator.
   template<typename _Iterator>
-    inline bool
+    _GLIBCXX20_CONSTEXPR inline bool
     __check_singular(const _Iterator& __x)
     { return __check_singular_aux(std::__addressof(__x)); }
 
   /** Non-NULL pointers are nonsingular. */
   template<typename _Tp>
-    inline bool
+    _GLIBCXX20_CONSTEXPR inline bool
     __check_singular(const _Tp* __ptr)
     { return __ptr == 0; }
 
@@ -71,7 +71,7 @@ namespace __gnu_debug
    * assertion statement because, e.g., we are in a constructor.
   */
   template<typename _InputIterator>
-    inline _InputIterator
+    _GLIBCXX20_CONSTEXPR inline _InputIterator
     __check_valid_range(const _InputIterator& __first,
 			const _InputIterator& __last,
 			const char* __file,
@@ -85,7 +85,7 @@ namespace __gnu_debug
 
   /* Handle the case where __other is a pointer to _Sequence::value_type. */
   template<typename _Iterator, typename _Sequence, typename _Category>
-    inline bool
+    _GLIBCXX20_CONSTEXPR inline bool
     __foreign_iterator_aux4(
 	const _Safe_iterator<_Iterator, _Sequence, _Category>& __it,
 	const typename _Sequence::value_type* __other)
@@ -107,7 +107,7 @@ namespace __gnu_debug
 
   /* Fallback overload for when we can't tell, assume it is valid. */
   template<typename _Iterator, typename _Sequence, typename _Category>
-    inline bool
+    _GLIBCXX20_CONSTEXPR inline bool
     __foreign_iterator_aux4(
 	const _Safe_iterator<_Iterator, _Sequence, _Category>&, ...)
     { return true; }
@@ -115,7 +115,7 @@ namespace __gnu_debug
   /* Handle sequences with contiguous storage */
   template<typename _Iterator, typename _Sequence, typename _Category,
 	   typename _InputIterator>
-    inline bool
+    _GLIBCXX20_CONSTEXPR inline bool
     __foreign_iterator_aux3(
 	const _Safe_iterator<_Iterator, _Sequence, _Category>& __it,
 	const _InputIterator& __other, const _InputIterator& __other_end,
@@ -131,7 +131,7 @@ namespace __gnu_debug
   /* Handle non-contiguous containers, assume it is valid. */
   template<typename _Iterator, typename _Sequence, typename _Category,
 	   typename _InputIterator>
-    inline bool
+    _GLIBCXX20_CONSTEXPR inline bool
     __foreign_iterator_aux3(
 	const _Safe_iterator<_Iterator, _Sequence, _Category>&,
 	const _InputIterator&, const _InputIterator&,
@@ -141,7 +141,7 @@ namespace __gnu_debug
   /** Handle debug iterators from the same type of container. */
   template<typename _Iterator, typename _Sequence, typename _Category,
 	   typename _OtherIterator>
-    inline bool
+    _GLIBCXX20_CONSTEXPR inline bool
     __foreign_iterator_aux2(
 	const _Safe_iterator<_Iterator, _Sequence, _Category>& __it,
 	const _Safe_iterator<_OtherIterator, _Sequence, _Category>& __other,
@@ -152,7 +152,7 @@ namespace __gnu_debug
   template<typename _Iterator, typename _Sequence, typename _Category,
 	   typename _OtherIterator, typename _OtherSequence,
 	   typename _OtherCategory>
-    inline bool
+    _GLIBCXX20_CONSTEXPR inline bool
     __foreign_iterator_aux2(
 	const _Safe_iterator<_Iterator, _Sequence, _Category>&,
 	const _Safe_iterator<_OtherIterator, _OtherSequence,
@@ -164,7 +164,7 @@ namespace __gnu_debug
   /* Handle non-debug iterators. */
   template<typename _Iterator, typename _Sequence, typename _Category,
 	   typename _InputIterator>
-    inline bool
+    _GLIBCXX20_CONSTEXPR inline bool
     __foreign_iterator_aux2(
 	const _Safe_iterator<_Iterator, _Sequence, _Category>& __it,
 	const _InputIterator& __other,
@@ -185,7 +185,7 @@ namespace __gnu_debug
   /* Handle the case where we aren't really inserting a range after all */
   template<typename _Iterator, typename _Sequence, typename _Category,
 	   typename _Integral>
-    inline bool
+    _GLIBCXX20_CONSTEXPR inline bool
     __foreign_iterator_aux(
 	const _Safe_iterator<_Iterator, _Sequence, _Category>&,
 	_Integral, _Integral, std::__true_type)
@@ -194,7 +194,7 @@ namespace __gnu_debug
   /* Handle all iterators. */
   template<typename _Iterator, typename _Sequence, typename _Category,
 	   typename _InputIterator>
-    inline bool
+    _GLIBCXX20_CONSTEXPR inline bool
     __foreign_iterator_aux(
 	const _Safe_iterator<_Iterator, _Sequence, _Category>& __it,
 	_InputIterator __other, _InputIterator __other_end,
@@ -207,7 +207,7 @@ namespace __gnu_debug
 
   template<typename _Iterator, typename _Sequence, typename _Category,
 	   typename _InputIterator>
-    inline bool
+    _GLIBCXX20_CONSTEXPR inline bool
     __foreign_iterator(
 	const _Safe_iterator<_Iterator, _Sequence, _Category>& __it,
 	_InputIterator __other, _InputIterator __other_end)
@@ -219,7 +219,7 @@ namespace __gnu_debug
   // Can't check if an input iterator sequence is sorted, because we
   // can't step through the sequence.
   template<typename _InputIterator>
-    inline bool
+    _GLIBCXX20_CONSTEXPR inline bool
     __check_sorted_aux(const _InputIterator&, const _InputIterator&,
                        std::input_iterator_tag)
     { return true; }
@@ -227,7 +227,7 @@ namespace __gnu_debug
   // Can verify if a forward iterator sequence is in fact sorted using
   // std::__is_sorted
   template<typename _ForwardIterator>
-    inline bool
+    _GLIBCXX20_CONSTEXPR inline bool
     __check_sorted_aux(_ForwardIterator __first, _ForwardIterator __last,
                        std::forward_iterator_tag)
     {
@@ -245,7 +245,7 @@ namespace __gnu_debug
   // Can't check if an input iterator sequence is sorted, because we can't step
   // through the sequence.
   template<typename _InputIterator, typename _Predicate>
-    inline bool
+    _GLIBCXX20_CONSTEXPR inline bool
     __check_sorted_aux(const _InputIterator&, const _InputIterator&,
                        _Predicate, std::input_iterator_tag)
     { return true; }
@@ -253,7 +253,7 @@ namespace __gnu_debug
   // Can verify if a forward iterator sequence is in fact sorted using
   // std::__is_sorted
   template<typename _ForwardIterator, typename _Predicate>
-    inline bool
+    _GLIBCXX20_CONSTEXPR inline bool
     __check_sorted_aux(_ForwardIterator __first, _ForwardIterator __last,
                        _Predicate __pred, std::forward_iterator_tag)
     {
@@ -270,7 +270,7 @@ namespace __gnu_debug
 
   // Determine if a sequence is sorted.
   template<typename _InputIterator>
-    inline bool
+    _GLIBCXX20_CONSTEXPR inline bool
     __check_sorted(const _InputIterator& __first, const _InputIterator& __last)
     {
       // Verify that the < operator for elements in the sequence is a
@@ -282,7 +282,7 @@ namespace __gnu_debug
     }
 
   template<typename _InputIterator, typename _Predicate>
-    inline bool
+    _GLIBCXX20_CONSTEXPR inline bool
     __check_sorted(const _InputIterator& __first, const _InputIterator& __last,
                    _Predicate __pred)
     {
@@ -295,28 +295,28 @@ namespace __gnu_debug
     }
 
   template<typename _InputIterator>
-    inline bool
+    _GLIBCXX20_CONSTEXPR inline bool
     __check_sorted_set_aux(const _InputIterator& __first,
 			   const _InputIterator& __last,
 			   std::__true_type)
     { return __check_sorted(__first, __last); }
 
   template<typename _InputIterator>
-    inline bool
+    _GLIBCXX20_CONSTEXPR inline bool
     __check_sorted_set_aux(const _InputIterator&,
 			   const _InputIterator&,
 			   std::__false_type)
     { return true; }
 
   template<typename _InputIterator, typename _Predicate>
-    inline bool
+    _GLIBCXX20_CONSTEXPR inline bool
     __check_sorted_set_aux(const _InputIterator& __first,
 			   const _InputIterator& __last,
 			   _Predicate __pred, std::__true_type)
     { return __check_sorted(__first, __last, __pred); }
 
   template<typename _InputIterator, typename _Predicate>
-    inline bool
+    _GLIBCXX20_CONSTEXPR inline bool
     __check_sorted_set_aux(const _InputIterator&,
 			   const _InputIterator&, _Predicate,
 			   std::__false_type)
@@ -324,7 +324,7 @@ namespace __gnu_debug
 
   // ... special variant used in std::merge, std::includes, std::set_*.
   template<typename _InputIterator1, typename _InputIterator2>
-    inline bool
+    _GLIBCXX20_CONSTEXPR inline bool
     __check_sorted_set(const _InputIterator1& __first,
 		       const _InputIterator1& __last,
 		       const _InputIterator2&)
@@ -341,7 +341,7 @@ namespace __gnu_debug
 
   template<typename _InputIterator1, typename _InputIterator2,
 	   typename _Predicate>
-    inline bool
+    _GLIBCXX20_CONSTEXPR inline bool
     __check_sorted_set(const _InputIterator1& __first,
 		       const _InputIterator1& __last,
 		       const _InputIterator2&, _Predicate __pred)
@@ -360,7 +360,7 @@ namespace __gnu_debug
   // 270. Binary search requirements overly strict
   // Determine if a sequence is partitioned w.r.t. this element.
   template<typename _ForwardIterator, typename _Tp>
-    inline bool
+    _GLIBCXX20_CONSTEXPR inline bool
     __check_partitioned_lower(_ForwardIterator __first,
 			      _ForwardIterator __last, const _Tp& __value)
     {
@@ -376,7 +376,7 @@ namespace __gnu_debug
     }
 
   template<typename _ForwardIterator, typename _Tp>
-    inline bool
+    _GLIBCXX20_CONSTEXPR inline bool
     __check_partitioned_upper(_ForwardIterator __first,
 			      _ForwardIterator __last, const _Tp& __value)
     {
@@ -393,7 +393,7 @@ namespace __gnu_debug
 
   // Determine if a sequence is partitioned w.r.t. this element.
   template<typename _ForwardIterator, typename _Tp, typename _Pred>
-    inline bool
+    _GLIBCXX20_CONSTEXPR inline bool
     __check_partitioned_lower(_ForwardIterator __first,
 			      _ForwardIterator __last, const _Tp& __value,
 			      _Pred __pred)
@@ -410,7 +410,7 @@ namespace __gnu_debug
     }
 
   template<typename _ForwardIterator, typename _Tp, typename _Pred>
-    inline bool
+    _GLIBCXX20_CONSTEXPR inline bool
     __check_partitioned_upper(_ForwardIterator __first,
 			      _ForwardIterator __last, const _Tp& __value,
 			      _Pred __pred)
@@ -435,36 +435,36 @@ namespace __gnu_debug
 
     template<typename _It,
 	     typename = decltype(__deref<_It>() < __deref<_It>())>
-      static bool
+      _GLIBCXX20_CONSTEXPR static bool
       _S_is_valid(_It __it)
       { return !(*__it < *__it); }
 
     // Fallback method if operator doesn't exist.
     template<typename... _Args>
-      static bool
+      _GLIBCXX20_CONSTEXPR static bool
       _S_is_valid(_Args...)
       { return true; }
 
     template<typename _It, typename _Pred, typename
 	= decltype(std::declval<_Pred>()(__deref<_It>(), __deref<_It>()))>
-      static bool
+      _GLIBCXX20_CONSTEXPR static bool
       _S_is_valid_pred(_It __it, _Pred __pred)
       { return !__pred(*__it, *__it); }
 
     // Fallback method if predicate can't be invoked.
     template<typename... _Args>
-      static bool
+      _GLIBCXX20_CONSTEXPR static bool
       _S_is_valid_pred(_Args...)
       { return true; }
   };
 
   template<typename _Iterator>
-    inline bool
+    _GLIBCXX20_CONSTEXPR inline bool
     __is_irreflexive(_Iterator __it)
     { return _Irreflexive_checker::_S_is_valid(__it); }
 
   template<typename _Iterator, typename _Pred>
-    inline bool
+    _GLIBCXX20_CONSTEXPR inline bool
     __is_irreflexive_pred(_Iterator __it, _Pred __pred)
     { return _Irreflexive_checker::_S_is_valid_pred(__it, __pred); }
 #endif
diff --git a/libstdc++-v3/include/debug/helper_functions.h b/libstdc++-v3/include/debug/helper_functions.h
index b7aeafef12a..a8686701454 100644
--- a/libstdc++-v3/include/debug/helper_functions.h
+++ b/libstdc++-v3/include/debug/helper_functions.h
@@ -87,13 +87,13 @@ namespace __gnu_debug
    *	precision.
   */
   template<typename _Iterator>
-    inline typename _Distance_traits<_Iterator>::__type
+    _GLIBCXX20_CONSTEXPR inline typename _Distance_traits<_Iterator>::__type
     __get_distance(_Iterator __lhs, _Iterator __rhs,
 		   std::random_access_iterator_tag)
     { return std::make_pair(__rhs - __lhs, __dp_exact); }
 
   template<typename _Iterator>
-    inline typename _Distance_traits<_Iterator>::__type
+    _GLIBCXX20_CONSTEXPR inline typename _Distance_traits<_Iterator>::__type
     __get_distance(_Iterator __lhs, _Iterator __rhs,
 		   std::input_iterator_tag)
     {
@@ -104,7 +104,7 @@ namespace __gnu_debug
     }
 
   template<typename _Iterator>
-    inline typename _Distance_traits<_Iterator>::__type
+    _GLIBCXX20_CONSTEXPR inline typename _Distance_traits<_Iterator>::__type
     __get_distance(_Iterator __lhs, _Iterator __rhs)
     { return __get_distance(__lhs, __rhs, std::__iterator_category(__lhs)); }
 
@@ -113,7 +113,7 @@ namespace __gnu_debug
    *  iterators.
   */
   template<typename _Integral>
-    inline bool
+    _GLIBCXX20_CONSTEXPR inline bool
     __valid_range_aux(_Integral, _Integral,
 		      typename _Distance_traits<_Integral>::__type& __dist,
 		      std::__true_type)
@@ -126,7 +126,7 @@ namespace __gnu_debug
    *  to see if we can check the range ahead of time.
   */
   template<typename _InputIterator>
-    inline bool
+    _GLIBCXX20_CONSTEXPR inline bool
     __valid_range_aux(_InputIterator __first, _InputIterator __last,
 		      typename _Distance_traits<_InputIterator>::__type& __dist,
 		      std::__false_type)
@@ -155,7 +155,7 @@ namespace __gnu_debug
    *  otherwise.
   */
   template<typename _InputIterator>
-    inline bool
+    _GLIBCXX20_CONSTEXPR inline bool
     __valid_range(_InputIterator __first, _InputIterator __last,
 		  typename _Distance_traits<_InputIterator>::__type& __dist)
     {
@@ -164,21 +164,21 @@ namespace __gnu_debug
     }
 
   template<typename _Iterator, typename _Sequence, typename _Category>
-    bool
+    _GLIBCXX20_CONSTEXPR bool
     __valid_range(const _Safe_iterator<_Iterator, _Sequence, _Category>&,
 		  const _Safe_iterator<_Iterator, _Sequence, _Category>&,
 		  typename _Distance_traits<_Iterator>::__type&);
 
 #if __cplusplus >= 201103L
-  template<typename _Iterator,typename _Sequence>
-    bool
+  template<typename _Iterator, typename _Sequence>
+    _GLIBCXX20_CONSTEXPR bool
     __valid_range(const _Safe_local_iterator<_Iterator, _Sequence>&,
 		  const _Safe_local_iterator<_Iterator, _Sequence>&,
 		  typename _Distance_traits<_Iterator>::__type&);
 #endif
 
   template<typename _InputIterator>
-    inline bool
+    _GLIBCXX20_CONSTEXPR inline bool
     __valid_range(_InputIterator __first, _InputIterator __last)
     {
       typename _Distance_traits<_InputIterator>::__type __dist;
@@ -186,26 +186,26 @@ namespace __gnu_debug
     }
 
   template<typename _Iterator, typename _Sequence, typename _Category>
-    bool
+    _GLIBCXX20_CONSTEXPR bool
     __valid_range(const _Safe_iterator<_Iterator, _Sequence, _Category>&,
 		  const _Safe_iterator<_Iterator, _Sequence, _Category>&);
 
 #if __cplusplus >= 201103L
   template<typename _Iterator, typename _Sequence>
-    bool
+    _GLIBCXX20_CONSTEXPR bool
     __valid_range(const _Safe_local_iterator<_Iterator, _Sequence>&,
 		  const _Safe_local_iterator<_Iterator, _Sequence>&);
 #endif
 
   // Fallback method, always ok.
   template<typename _InputIterator, typename _Size>
-    inline bool
+    _GLIBCXX20_CONSTEXPR inline bool
     __can_advance(_InputIterator, _Size)
     { return true; }
 
   template<typename _Iterator, typename _Sequence, typename _Category,
 	   typename _Size>
-    bool
+    _GLIBCXX20_CONSTEXPR bool
     __can_advance(const _Safe_iterator<_Iterator, _Sequence, _Category>&,
 		  _Size);
 
@@ -216,7 +216,7 @@ namespace __gnu_debug
    *  thanks to the < operator.
    */
   template<typename _Iterator>
-    inline _Iterator
+    _GLIBCXX20_CONSTEXPR inline _Iterator
     __base(_Iterator __it)
     { return __it; }
 
@@ -228,7 +228,7 @@ namespace __gnu_debug
 
   /* Remove debug mode safe iterator layer, if any. */
   template<typename _Iterator>
-    inline _Iterator
+    _GLIBCXX20_CONSTEXPR inline _Iterator
     __unsafe(_Iterator __it)
     { return __it; }
 }
diff --git a/libstdc++-v3/include/debug/safe_iterator.h b/libstdc++-v3/include/debug/safe_iterator.h
index 6700eafca0b..0387367a08f 100644
--- a/libstdc++-v3/include/debug/safe_iterator.h
+++ b/libstdc++-v3/include/debug/safe_iterator.h
@@ -905,7 +905,7 @@ namespace __gnu_debug
 
   /** Safe iterators know how to check if they form a valid range. */
   template<typename _Iterator, typename _Sequence, typename _Category>
-    inline bool
+    _GLIBCXX20_CONSTEXPR inline bool
     __valid_range(const _Safe_iterator<_Iterator, _Sequence,
 				       _Category>& __first,
 		  const _Safe_iterator<_Iterator, _Sequence,
@@ -914,7 +914,7 @@ namespace __gnu_debug
     { return __first._M_valid_range(__last, __dist); }
 
   template<typename _Iterator, typename _Sequence, typename _Category>
-    inline bool
+    _GLIBCXX20_CONSTEXPR inline bool
     __valid_range(const _Safe_iterator<_Iterator, _Sequence,
 				       _Category>& __first,
 		  const _Safe_iterator<_Iterator, _Sequence,
@@ -926,13 +926,13 @@ namespace __gnu_debug
 
   template<typename _Iterator, typename _Sequence, typename _Category,
 	   typename _Size>
-    inline bool
+    _GLIBCXX20_CONSTEXPR inline bool
     __can_advance(const _Safe_iterator<_Iterator, _Sequence, _Category>& __it,
 		  _Size __n)
     { return __it._M_can_advance(__n); }
 
   template<typename _Iterator, typename _Sequence>
-    _Iterator
+    _GLIBCXX20_CONSTEXPR _Iterator
     __base(const _Safe_iterator<_Iterator, _Sequence,
 				std::random_access_iterator_tag>& __it)
     { return __it.base(); }
@@ -944,7 +944,7 @@ namespace __gnu_debug
 #endif
 
   template<typename _Iterator, typename _Sequence>
-    inline _Iterator
+    _GLIBCXX20_CONSTEXPR inline _Iterator
     __unsafe(const _Safe_iterator<_Iterator, _Sequence>& __it)
     { return __it.base(); }
 
diff --git a/libstdc++-v3/include/debug/safe_local_iterator.h b/libstdc++-v3/include/debug/safe_local_iterator.h
index 40919126c9f..299487241bc 100644
--- a/libstdc++-v3/include/debug/safe_local_iterator.h
+++ b/libstdc++-v3/include/debug/safe_local_iterator.h
@@ -403,14 +403,14 @@ namespace __gnu_debug
 
   /** Safe local iterators know how to check if they form a valid range. */
   template<typename _Iterator, typename _Sequence>
-    inline bool
+    _GLIBCXX20_CONSTEXPR inline bool
     __valid_range(const _Safe_local_iterator<_Iterator, _Sequence>& __first,
 		  const _Safe_local_iterator<_Iterator, _Sequence>& __last,
 		  typename _Distance_traits<_Iterator>::__type& __dist_info)
     { return __first._M_valid_range(__last, __dist_info); }
 
   template<typename _Iterator, typename _Sequence>
-    inline bool
+    _GLIBCXX20_CONSTEXPR inline bool
     __valid_range(const _Safe_local_iterator<_Iterator, _Sequence>& __first,
 		  const _Safe_local_iterator<_Iterator, _Sequence>& __last)
     {
@@ -425,7 +425,7 @@ namespace __gnu_debug
 #endif
 
   template<typename _Iterator, typename _Sequence>
-    inline _Iterator
+    _GLIBCXX20_CONSTEXPR inline _Iterator
     __unsafe(const _Safe_local_iterator<_Iterator, _Sequence>& __it)
     { return __it.base(); }