libstdc++: Call predicate with non-const values in std::erase_if [PR107850]

As specified in the standard, the predicate for std::erase_if has to be
invocable as non-const with a non-const lvalues argument. Restore
support for predicates that only accept non-const arguments.

It's not strictly nevessary to change it for the set and unordered_set
overloads, because they only give const access to the elements anyway.
I've done it for them too just to keep them all consistent.

libstdc++-v3/ChangeLog:

	PR libstdc++/107850
	* include/bits/erase_if.h (__erase_nodes_if): Use non-const
	reference to the container.
	* include/experimental/map (erase_if): Likewise.
	* include/experimental/set (erase_if): Likewise.
	* include/experimental/unordered_map (erase_if): Likewise.
	* include/experimental/unordered_set (erase_if): Likewise.
	* include/std/map (erase_if): Likewise.
	* include/std/set (erase_if): Likewise.
	* include/std/unordered_map (erase_if): Likewise.
	* include/std/unordered_set (erase_if): Likewise.
	* testsuite/23_containers/map/erasure.cc: Check with
	const-incorrect predicate.
	* testsuite/23_containers/set/erasure.cc: Likewise.
	* testsuite/23_containers/unordered_map/erasure.cc: Likewise.
	* testsuite/23_containers/unordered_set/erasure.cc: Likewise.
	* testsuite/experimental/map/erasure.cc: Likewise.
	* testsuite/experimental/set/erasure.cc: Likewise.
	* testsuite/experimental/unordered_map/erasure.cc: Likewise.
	* testsuite/experimental/unordered_set/erasure.cc: Likewise.

(cherry picked from commit f54ceb2062c7fef294f85ae093914fa6c7ca35b8)

17 files changed, 121 insertions, 21 deletions

diff --git a/libstdc++-v3/include/bits/erase_if.h b/libstdc++-v3/include/bits/erase_if.h
index 397207f..b336e26 100644
--- a/libstdc++-v3/include/bits/erase_if.h
+++ b/libstdc++-v3/include/bits/erase_if.h
@@ -49,7 +49,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     template<typename _Container, typename _UnsafeContainer,
 	     typename _Predicate>
       typename _Container::size_type
-      __erase_nodes_if(_Container& __cont, const _UnsafeContainer& __ucont,
+      __erase_nodes_if(_Container& __cont, _UnsafeContainer& __ucont,
 		       _Predicate __pred)
       {
 	typename _Container::size_type __num = 0;
diff --git a/libstdc++-v3/include/experimental/map b/libstdc++-v3/include/experimental/map
index 4936a66..4e615c7 100644
--- a/libstdc++-v3/include/experimental/map
+++ b/libstdc++-v3/include/experimental/map
@@ -51,8 +51,7 @@ inline namespace fundamentals_v2
     inline void
     erase_if(map<_Key, _Tp, _Compare, _Alloc>& __cont, _Predicate __pred)
     {
-      const _GLIBCXX_STD_C::map<_Key, _Tp, _Compare, _Alloc>&
-	__ucont = __cont;
+      _GLIBCXX_STD_C::map<_Key, _Tp, _Compare, _Alloc>& __ucont = __cont;
       std::__detail::__erase_nodes_if(__cont, __ucont, __pred);
     }
 
@@ -61,8 +60,7 @@ inline namespace fundamentals_v2
     inline void
     erase_if(multimap<_Key, _Tp, _Compare, _Alloc>& __cont, _Predicate __pred)
     {
-      const _GLIBCXX_STD_C::multimap<_Key, _Tp, _Compare, _Alloc>&
-	__ucont = __cont;
+      _GLIBCXX_STD_C::multimap<_Key, _Tp, _Compare, _Alloc>& __ucont = __cont;
       std::__detail::__erase_nodes_if(__cont, __ucont, __pred);
     }
 
diff --git a/libstdc++-v3/include/experimental/set b/libstdc++-v3/include/experimental/set
index aa43a2b2..3d46a0b 100644
--- a/libstdc++-v3/include/experimental/set
+++ b/libstdc++-v3/include/experimental/set
@@ -51,7 +51,7 @@ inline namespace fundamentals_v2
     inline void
     erase_if(set<_Key, _Compare, _Alloc>& __cont, _Predicate __pred)
     {
-      const _GLIBCXX_STD_C::set<_Key, _Compare, _Alloc>& __ucont = __cont;
+      _GLIBCXX_STD_C::set<_Key, _Compare, _Alloc>& __ucont = __cont;
       std::__detail::__erase_nodes_if(__cont, __ucont, __pred);
     }
 
@@ -60,7 +60,7 @@ inline namespace fundamentals_v2
     inline void
     erase_if(multiset<_Key, _Compare, _Alloc>& __cont, _Predicate __pred)
     {
-      const _GLIBCXX_STD_C::multiset<_Key, _Compare, _Alloc>& __ucont = __cont;
+      _GLIBCXX_STD_C::multiset<_Key, _Compare, _Alloc>& __ucont = __cont;
       std::__detail::__erase_nodes_if(__cont, __ucont, __pred);
     }
 
diff --git a/libstdc++-v3/include/experimental/unordered_map b/libstdc++-v3/include/experimental/unordered_map
index 1a41687..26fff83 100644
--- a/libstdc++-v3/include/experimental/unordered_map
+++ b/libstdc++-v3/include/experimental/unordered_map
@@ -52,7 +52,7 @@ inline namespace fundamentals_v2
     erase_if(unordered_map<_Key, _Tp, _Hash, _CPred, _Alloc>& __cont,
 	     _Predicate __pred)
     {
-      const _GLIBCXX_STD_C::unordered_map<_Key, _Tp, _Hash, _CPred, _Alloc>&
+      _GLIBCXX_STD_C::unordered_map<_Key, _Tp, _Hash, _CPred, _Alloc>&
 	__ucont = __cont;
       std::__detail::__erase_nodes_if(__cont, __ucont, __pred);
     }
@@ -63,7 +63,7 @@ inline namespace fundamentals_v2
     erase_if(unordered_multimap<_Key, _Tp, _Hash, _CPred, _Alloc>& __cont,
 	     _Predicate __pred)
     {
-      const _GLIBCXX_STD_C::unordered_multimap<_Key, _Tp, _Hash, _CPred, _Alloc>&
+      _GLIBCXX_STD_C::unordered_multimap<_Key, _Tp, _Hash, _CPred, _Alloc>&
 	__ucont = __cont;
       std::__detail::__erase_nodes_if(__cont, __ucont, __pred);
     }
diff --git a/libstdc++-v3/include/experimental/unordered_set b/libstdc++-v3/include/experimental/unordered_set
index 583c437..22fe49d 100644
--- a/libstdc++-v3/include/experimental/unordered_set
+++ b/libstdc++-v3/include/experimental/unordered_set
@@ -52,7 +52,7 @@ inline namespace fundamentals_v2
     erase_if(unordered_set<_Key, _Hash, _CPred, _Alloc>& __cont,
 	     _Predicate __pred)
     {
-      const _GLIBCXX_STD_C::unordered_set<_Key, _Hash, _CPred, _Alloc>&
+      _GLIBCXX_STD_C::unordered_set<_Key, _Hash, _CPred, _Alloc>&
 	__ucont = __cont;
       std::__detail::__erase_nodes_if(__cont, __ucont, __pred);
     }
@@ -63,7 +63,7 @@ inline namespace fundamentals_v2
     erase_if(unordered_multiset<_Key, _Hash, _CPred, _Alloc>& __cont,
 	     _Predicate __pred)
     {
-      const _GLIBCXX_STD_C::unordered_multiset<_Key, _Hash, _CPred, _Alloc>&
+      _GLIBCXX_STD_C::unordered_multiset<_Key, _Hash, _CPred, _Alloc>&
 	__ucont = __cont;
       std::__detail::__erase_nodes_if(__cont, __ucont, __pred);
     }
diff --git a/libstdc++-v3/include/std/map b/libstdc++-v3/include/std/map
index 93c956a..1311d61 100644
--- a/libstdc++-v3/include/std/map
+++ b/libstdc++-v3/include/std/map
@@ -96,8 +96,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     inline typename map<_Key, _Tp, _Compare, _Alloc>::size_type
     erase_if(map<_Key, _Tp, _Compare, _Alloc>& __cont, _Predicate __pred)
     {
-      const _GLIBCXX_STD_C::map<_Key, _Tp, _Compare, _Alloc>&
-	__ucont = __cont;
+      _GLIBCXX_STD_C::map<_Key, _Tp, _Compare, _Alloc>& __ucont = __cont;
       return __detail::__erase_nodes_if(__cont, __ucont, __pred);
     }
 
@@ -106,8 +105,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     inline typename multimap<_Key, _Tp, _Compare, _Alloc>::size_type
     erase_if(multimap<_Key, _Tp, _Compare, _Alloc>& __cont, _Predicate __pred)
     {
-      const _GLIBCXX_STD_C::multimap<_Key, _Tp, _Compare, _Alloc>&
-	__ucont = __cont;
+      _GLIBCXX_STD_C::multimap<_Key, _Tp, _Compare, _Alloc>& __ucont = __cont;
       return __detail::__erase_nodes_if(__cont, __ucont, __pred);
     }
 _GLIBCXX_END_NAMESPACE_VERSION
diff --git a/libstdc++-v3/include/std/set b/libstdc++-v3/include/std/set
index 45fed14..7512791 100644
--- a/libstdc++-v3/include/std/set
+++ b/libstdc++-v3/include/std/set
@@ -92,7 +92,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     inline typename set<_Key, _Compare, _Alloc>::size_type
     erase_if(set<_Key, _Compare, _Alloc>& __cont, _Predicate __pred)
     {
-      const _GLIBCXX_STD_C::set<_Key, _Compare, _Alloc>& __ucont = __cont;
+      _GLIBCXX_STD_C::set<_Key, _Compare, _Alloc>& __ucont = __cont;
       return __detail::__erase_nodes_if(__cont, __ucont, __pred);
     }
 
@@ -101,7 +101,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     inline typename multiset<_Key, _Compare, _Alloc>::size_type
     erase_if(multiset<_Key, _Compare, _Alloc>& __cont, _Predicate __pred)
     {
-      const _GLIBCXX_STD_C::multiset<_Key, _Compare, _Alloc>& __ucont = __cont;
+      _GLIBCXX_STD_C::multiset<_Key, _Compare, _Alloc>& __ucont = __cont;
       return __detail::__erase_nodes_if(__cont, __ucont, __pred);
     }
 _GLIBCXX_END_NAMESPACE_VERSION
diff --git a/libstdc++-v3/include/std/unordered_map b/libstdc++-v3/include/std/unordered_map
index bb14ffa..d57e8dd 100644
--- a/libstdc++-v3/include/std/unordered_map
+++ b/libstdc++-v3/include/std/unordered_map
@@ -84,7 +84,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     erase_if(unordered_map<_Key, _Tp, _Hash, _CPred, _Alloc>& __cont,
 	     _Predicate __pred)
     {
-      const _GLIBCXX_STD_C::unordered_map<_Key, _Tp, _Hash, _CPred, _Alloc>&
+      _GLIBCXX_STD_C::unordered_map<_Key, _Tp, _Hash, _CPred, _Alloc>&
 	__ucont = __cont;
       return __detail::__erase_nodes_if(__cont, __ucont, __pred);
     }
@@ -96,7 +96,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     erase_if(unordered_multimap<_Key, _Tp, _Hash, _CPred, _Alloc>& __cont,
 	     _Predicate __pred)
     {
-      const _GLIBCXX_STD_C::unordered_multimap<_Key, _Tp, _Hash, _CPred, _Alloc>&
+      _GLIBCXX_STD_C::unordered_multimap<_Key, _Tp, _Hash, _CPred, _Alloc>&
 	__ucont = __cont;
       return __detail::__erase_nodes_if(__cont, __ucont, __pred);
     }
diff --git a/libstdc++-v3/include/std/unordered_set b/libstdc++-v3/include/std/unordered_set
index 777e3b8..a86a80c 100644
--- a/libstdc++-v3/include/std/unordered_set
+++ b/libstdc++-v3/include/std/unordered_set
@@ -84,7 +84,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     erase_if(unordered_set<_Key, _Hash, _CPred, _Alloc>& __cont,
 	     _Predicate __pred)
     {
-      const _GLIBCXX_STD_C::unordered_set<_Key, _Hash, _CPred, _Alloc>&
+      _GLIBCXX_STD_C::unordered_set<_Key, _Hash, _CPred, _Alloc>&
 	__ucont = __cont;
       return __detail::__erase_nodes_if(__cont, __ucont, __pred);
     }
@@ -95,7 +95,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     erase_if(unordered_multiset<_Key, _Hash, _CPred, _Alloc>& __cont,
 	     _Predicate __pred)
     {
-      const _GLIBCXX_STD_C::unordered_multiset<_Key, _Hash, _CPred, _Alloc>&
+      _GLIBCXX_STD_C::unordered_multiset<_Key, _Hash, _CPred, _Alloc>&
 	__ucont = __cont;
       return __detail::__erase_nodes_if(__cont, __ucont, __pred);
     }
diff --git a/libstdc++-v3/testsuite/23_containers/map/erasure.cc b/libstdc++-v3/testsuite/23_containers/map/erasure.cc
index badf789..643ad0a 100644
--- a/libstdc++-v3/testsuite/23_containers/map/erasure.cc
+++ b/libstdc++-v3/testsuite/23_containers/map/erasure.cc
@@ -61,11 +61,24 @@ test02()
   VERIFY( num == 4 );
 }
 
+void
+test_pr107850()
+{
+  // Predicate only callable as non-const and only accepts non-const argument.
+  struct Pred { bool operator()(std::pair<const int, int>&) { return false; } };
+  const Pred pred; // erase_if parameter is passed by value, so non-const.
+  std::map<int, int> m;
+  std::erase_if(m, pred);
+  std::multimap<int, int> mm;
+  std::erase_if(mm, pred);
+}
+
 int
 main()
 {
   test01();
   test02();
+  test_pr107850();
 
   return 0;
 }
diff --git a/libstdc++-v3/testsuite/23_containers/set/erasure.cc b/libstdc++-v3/testsuite/23_containers/set/erasure.cc
index fe0c4b8..bfa28f2 100644
--- a/libstdc++-v3/testsuite/23_containers/set/erasure.cc
+++ b/libstdc++-v3/testsuite/23_containers/set/erasure.cc
@@ -49,11 +49,24 @@ test02()
   VERIFY( num == 4 );
 }
 
+void
+test_pr107850()
+{
+  // Predicate only callable as non-const.
+  struct Pred { bool operator()(const int&) { return false; } };
+  const Pred pred; // erase_if parameter is passed by value, so non-const.
+  std::set<int> s;
+  std::erase_if(s, pred);
+  std::multiset<int> ms;
+  std::erase_if(ms, pred);
+}
+
 int
 main()
 {
   test01();
   test02();
+  test_pr107850();
 
   return 0;
 }
diff --git a/libstdc++-v3/testsuite/23_containers/unordered_map/erasure.cc b/libstdc++-v3/testsuite/23_containers/unordered_map/erasure.cc
index e6018186..8392e53 100644
--- a/libstdc++-v3/testsuite/23_containers/unordered_map/erasure.cc
+++ b/libstdc++-v3/testsuite/23_containers/unordered_map/erasure.cc
@@ -61,11 +61,24 @@ test02()
   VERIFY( num == 4 );
 }
 
+void
+test_pr107850()
+{
+  // Predicate only callable as non-const and only accepts non-const argument.
+  struct Pred { bool operator()(std::pair<const int, int>&) { return false; } };
+  const Pred pred; // erase_if parameter is passed by value, so non-const.
+  std::unordered_map<int, int> m;
+  std::erase_if(m, pred);
+  std::unordered_multimap<int, int> mm;
+  std::erase_if(mm, pred);
+}
+
 int
 main()
 {
   test01();
   test02();
+  test_pr107850();
 
   return 0;
 }
diff --git a/libstdc++-v3/testsuite/23_containers/unordered_set/erasure.cc b/libstdc++-v3/testsuite/23_containers/unordered_set/erasure.cc
index 4cb8041..7684549 100644
--- a/libstdc++-v3/testsuite/23_containers/unordered_set/erasure.cc
+++ b/libstdc++-v3/testsuite/23_containers/unordered_set/erasure.cc
@@ -51,11 +51,24 @@ test02()
   VERIFY( num == 4 );
 }
 
+void
+test_pr107850()
+{
+  // Predicate only callable as non-const.
+  struct Pred { bool operator()(const int&) { return false; } };
+  const Pred pred; // erase_if parameter is passed by value, so non-const.
+  std::unordered_set<int> s;
+  std::erase_if(s, pred);
+  std::unordered_multiset<int> ms;
+  std::erase_if(ms, pred);
+}
+
 int
 main()
 {
   test01();
   test02();
+  test_pr107850();
 
   return 0;
 }
diff --git a/libstdc++-v3/testsuite/experimental/map/erasure.cc b/libstdc++-v3/testsuite/experimental/map/erasure.cc
index 8470ab2..b377926 100644
--- a/libstdc++-v3/testsuite/experimental/map/erasure.cc
+++ b/libstdc++-v3/testsuite/experimental/map/erasure.cc
@@ -52,11 +52,24 @@ test02()
   VERIFY( mm == t );
 }
 
+void
+test_pr107850()
+{
+  // Predicate only callable as non-const and only accepts non-const argument.
+  struct Pred { bool operator()(std::pair<const int, int>&) { return false; } };
+  const Pred pred; // erase_if parameter is passed by value, so non-const.
+  std::map<int, int> m;
+  std::experimental::erase_if(m, pred);
+  std::multimap<int, int> mm;
+  std::experimental::erase_if(mm, pred);
+}
+
 int
 main()
 {
   test01();
   test02();
+  test_pr107850();
 
   return 0;
 }
diff --git a/libstdc++-v3/testsuite/experimental/set/erasure.cc b/libstdc++-v3/testsuite/experimental/set/erasure.cc
index 1e04c34..b427228 100644
--- a/libstdc++-v3/testsuite/experimental/set/erasure.cc
+++ b/libstdc++-v3/testsuite/experimental/set/erasure.cc
@@ -40,11 +40,24 @@ test02()
   VERIFY( ms == t );
 }
 
+void
+test_pr107850()
+{
+  // Predicate only callable as non-const.
+  struct Pred { bool operator()(const int&) { return false; } };
+  const Pred pred; // erase_if parameter is passed by value, so non-const.
+  std::set<int> s;
+  std::experimental::erase_if(s, pred);
+  std::multiset<int> ms;
+  std::experimental::erase_if(ms, pred);
+}
+
 int
 main()
 {
   test01();
   test02();
+  test_pr107850();
 
   return 0;
 }
diff --git a/libstdc++-v3/testsuite/experimental/unordered_map/erasure.cc b/libstdc++-v3/testsuite/experimental/unordered_map/erasure.cc
index 022f575..cd281bc 100644
--- a/libstdc++-v3/testsuite/experimental/unordered_map/erasure.cc
+++ b/libstdc++-v3/testsuite/experimental/unordered_map/erasure.cc
@@ -52,11 +52,24 @@ test02()
   VERIFY( umm == t );
 }
 
+void
+test_pr107850()
+{
+  // Predicate only callable as non-const and only accepts non-const argument.
+  struct Pred { bool operator()(std::pair<const int, int>&) { return false; } };
+  const Pred pred; // erase_if parameter is passed by value, so non-const.
+  std::unordered_map<int, int> m;
+  std::experimental::erase_if(m, pred);
+  std::unordered_multimap<int, int> mm;
+  std::experimental::erase_if(mm, pred);
+}
+
 int
 main()
 {
   test01();
   test02();
+  test_pr107850();
 
   return 0;
 }
diff --git a/libstdc++-v3/testsuite/experimental/unordered_set/erasure.cc b/libstdc++-v3/testsuite/experimental/unordered_set/erasure.cc
index d261812..918f455 100644
--- a/libstdc++-v3/testsuite/experimental/unordered_set/erasure.cc
+++ b/libstdc++-v3/testsuite/experimental/unordered_set/erasure.cc
@@ -42,11 +42,24 @@ test02()
   VERIFY( ums == t );
 }
 
+void
+test_pr107850()
+{
+  // Predicate only callable as non-const.
+  struct Pred { bool operator()(const int&) { return false; } };
+  const Pred pred; // erase_if parameter is passed by value, so non-const.
+  std::unordered_set<int> s;
+  std::experimental::erase_if(s, pred);
+  std::unordered_multiset<int> ms;
+  std::experimental::erase_if(ms, pred);
+}
+
 int
 main()
 {
   test01();
   test02();
+  test_pr107850();
 
   return 0;
 }