From 188588e443008dd7795947db60b68571ed724fe3 Mon Sep 17 00:00:00 2001
From: Edward Smith-Rowland <3dw4rd@verizon.net>
Date: Wed, 28 Nov 2018 16:44:25 +0000
Subject: [PATCH] Implement uniform container erasure for C++20.

2018-11-28  Edward Smith-Rowland  <3dw4rd@verizon.net>

	Implement uniform container erasure for C++20.
	* include/Makefile.am: Move erase_if.h.
	* include/Makefile.in: Move erase_if.h.
	* include/experimental/bits/erase_if.h: Move ...
	* include/bits/erase_if.h: ... here.
	* include/experimental/map: Move erase_if.h.
	* include/experimental/set: Move erase_if.h.
	* include/experimental/unordered_map: Move erase_if.h.
	* include/experimental/unordered_set: Move erase_if.h.
	* include/std/deque (erase_if, erase): New functions.
	* include/std/forward_list: Ditto.
	* include/std/list: Ditto.
	* include/std/map: Ditto.
	* include/std/set: Ditto.
	* include/std/string: Ditto.
	* include/std/unordered_map: Ditto.
	* include/std/unordered_set: Ditto.
	* include/std/vector: Ditto.
	* testsuite/21_strings/basic_string/erasure.cc: New test.
	* testsuite/23_containers/deque/erasure.cc: New test.
	* testsuite/23_containers/forward_list/erasure.cc: New test.
	* testsuite/23_containers/list/erasure.cc: New test.
	* testsuite/23_containers/map/erasure.cc: New test.
	* testsuite/23_containers/set/erasure.cc: New test.
	* testsuite/23_containers/unordered_map/erasure.cc: New test.
	* testsuite/23_containers/unordered_set/erasure.cc: New test.
	* testsuite/23_containers/vector/erasure.cc: New test.

From-SVN: r266567
---
 libstdc++-v3/ChangeLog                        | 30 +++++++++
 libstdc++-v3/include/Makefile.am              |  2 +-
 libstdc++-v3/include/Makefile.in              |  2 +-
 .../{experimental => }/bits/erase_if.h        | 17 ++----
 libstdc++-v3/include/experimental/map         |  6 +-
 libstdc++-v3/include/experimental/set         |  6 +-
 .../include/experimental/unordered_map        |  6 +-
 .../include/experimental/unordered_set        |  6 +-
 libstdc++-v3/include/std/deque                | 23 +++++++
 libstdc++-v3/include/std/forward_list         | 21 +++++++
 libstdc++-v3/include/std/list                 | 21 +++++++
 libstdc++-v3/include/std/map                  | 20 ++++++
 libstdc++-v3/include/std/set                  | 20 ++++++
 libstdc++-v3/include/std/string               | 25 ++++++++
 libstdc++-v3/include/std/unordered_map        | 23 +++++++
 libstdc++-v3/include/std/unordered_set        | 10 +++
 libstdc++-v3/include/std/vector               | 23 +++++++
 .../21_strings/basic_string/erasure.cc        | 53 ++++++++++++++++
 .../testsuite/23_containers/deque/erasure.cc  | 52 ++++++++++++++++
 .../23_containers/forward_list/erasure.cc     | 52 ++++++++++++++++
 .../testsuite/23_containers/list/erasure.cc   | 52 ++++++++++++++++
 .../testsuite/23_containers/map/erasure.cc    | 61 +++++++++++++++++++
 .../testsuite/23_containers/set/erasure.cc    | 50 +++++++++++++++
 .../23_containers/unordered_map/erasure.cc    | 61 +++++++++++++++++++
 .../23_containers/unordered_set/erasure.cc    | 52 ++++++++++++++++
 .../testsuite/23_containers/vector/erasure.cc | 52 ++++++++++++++++
 26 files changed, 720 insertions(+), 26 deletions(-)
 rename libstdc++-v3/include/{experimental => }/bits/erase_if.h (81%)
 create mode 100644 libstdc++-v3/testsuite/21_strings/basic_string/erasure.cc
 create mode 100644 libstdc++-v3/testsuite/23_containers/deque/erasure.cc
 create mode 100644 libstdc++-v3/testsuite/23_containers/forward_list/erasure.cc
 create mode 100644 libstdc++-v3/testsuite/23_containers/list/erasure.cc
 create mode 100644 libstdc++-v3/testsuite/23_containers/map/erasure.cc
 create mode 100644 libstdc++-v3/testsuite/23_containers/set/erasure.cc
 create mode 100644 libstdc++-v3/testsuite/23_containers/unordered_map/erasure.cc
 create mode 100644 libstdc++-v3/testsuite/23_containers/unordered_set/erasure.cc
 create mode 100644 libstdc++-v3/testsuite/23_containers/vector/erasure.cc

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 9ef71f13897..dc989bc744f 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,33 @@
+2018-11-28  Edward Smith-Rowland  <3dw4rd@verizon.net>
+
+	Implement uniform container erasure for C++20.
+	* include/Makefile.am: Move erase_if.h.
+	* include/Makefile.in: Move erase_if.h.
+	* include/experimental/bits/erase_if.h: Move ...
+	* include/bits/erase_if.h: ... here.
+	* include/experimental/map: Move erase_if.h.
+	* include/experimental/set: Move erase_if.h.
+	* include/experimental/unordered_map: Move erase_if.h.
+	* include/experimental/unordered_set: Move erase_if.h.
+	* include/std/deque (erase_if, erase): New functions.
+	* include/std/forward_list: Ditto.
+	* include/std/list: Ditto.
+	* include/std/map: Ditto.
+	* include/std/set: Ditto.
+	* include/std/string: Ditto.
+	* include/std/unordered_map: Ditto.
+	* include/std/unordered_set: Ditto.
+	* include/std/vector: Ditto.
+	* testsuite/21_strings/basic_string/erasure.cc: New test.
+	* testsuite/23_containers/deque/erasure.cc: New test.
+	* testsuite/23_containers/forward_list/erasure.cc: New test.
+	* testsuite/23_containers/list/erasure.cc: New test.
+	* testsuite/23_containers/map/erasure.cc: New test.
+	* testsuite/23_containers/set/erasure.cc: New test.
+	* testsuite/23_containers/unordered_map/erasure.cc: New test.
+	* testsuite/23_containers/unordered_set/erasure.cc: New test.
+	* testsuite/23_containers/vector/erasure.cc: New test.
+
 2018-11-28  Jonathan Wakely  <jwakely@redhat.com>
 
 	* doc/xml/manual/intro.xml: Document LWG 3096 change.
diff --git a/libstdc++-v3/include/Makefile.am b/libstdc++-v3/include/Makefile.am
index d45d937d3a7..09aa1892a14 100644
--- a/libstdc++-v3/include/Makefile.am
+++ b/libstdc++-v3/include/Makefile.am
@@ -106,6 +106,7 @@ bits_headers = \
 	${bits_srcdir}/cpp_type_traits.h \
 	${bits_srcdir}/deque.tcc \
 	${bits_srcdir}/enable_special_members.h \
+	${bits_srcdir}/erase_if.h \
 	${bits_srcdir}/forward_list.h \
 	${bits_srcdir}/forward_list.tcc \
 	${bits_srcdir}/fs_dir.h \
@@ -710,7 +711,6 @@ experimental_headers = \
 experimental_bits_srcdir = ${glibcxx_srcdir}/include/experimental/bits
 experimental_bits_builddir = ./experimental/bits
 experimental_bits_headers = \
-	${experimental_bits_srcdir}/erase_if.h \
 	${experimental_bits_srcdir}/lfts_config.h \
 	${experimental_bits_srcdir}/net.h \
 	${experimental_bits_srcdir}/shared_ptr.h \
diff --git a/libstdc++-v3/include/Makefile.in b/libstdc++-v3/include/Makefile.in
index 9a1df294479..4d2642c8b78 100644
--- a/libstdc++-v3/include/Makefile.in
+++ b/libstdc++-v3/include/Makefile.in
@@ -449,6 +449,7 @@ bits_headers = \
 	${bits_srcdir}/cpp_type_traits.h \
 	${bits_srcdir}/deque.tcc \
 	${bits_srcdir}/enable_special_members.h \
+	${bits_srcdir}/erase_if.h \
 	${bits_srcdir}/forward_list.h \
 	${bits_srcdir}/forward_list.tcc \
 	${bits_srcdir}/fs_dir.h \
@@ -1052,7 +1053,6 @@ experimental_headers = \
 experimental_bits_srcdir = ${glibcxx_srcdir}/include/experimental/bits
 experimental_bits_builddir = ./experimental/bits
 experimental_bits_headers = \
-	${experimental_bits_srcdir}/erase_if.h \
 	${experimental_bits_srcdir}/lfts_config.h \
 	${experimental_bits_srcdir}/net.h \
 	${experimental_bits_srcdir}/shared_ptr.h \
diff --git a/libstdc++-v3/include/experimental/bits/erase_if.h b/libstdc++-v3/include/bits/erase_if.h
similarity index 81%
rename from libstdc++-v3/include/experimental/bits/erase_if.h
rename to libstdc++-v3/include/bits/erase_if.h
index 62ffbc130e7..de4601f0173 100644
--- a/libstdc++-v3/include/experimental/bits/erase_if.h
+++ b/libstdc++-v3/include/bits/erase_if.h
@@ -1,4 +1,4 @@
-// <experimental/bits/erase_if.h> -*- C++ -*-
+// <bits/erase_if.h> -*- C++ -*-
 
 // Copyright (C) 2015-2018 Free Software Foundation, Inc.
 //
@@ -22,27 +22,22 @@
 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 // <http://www.gnu.org/licenses/>.
 
-/** @file experimental/bits/erase_if.h
+/** @file bits/erase_if.h
  *  This is an internal header file, included by other library headers.
  *  Do not attempt to use it directly.
  */
 
-#ifndef _GLIBCXX_EXPERIMENTAL_ERASE_IF_H
-#define _GLIBCXX_EXPERIMENTAL_ERASE_IF_H 1
+#ifndef _GLIBCXX_ERASE_IF_H
+#define _GLIBCXX_ERASE_IF_H 1
 
 #pragma GCC system_header
 
 #if __cplusplus >= 201402L
-#include <experimental/bits/lfts_config.h>
 
 namespace std
 {
 _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
-namespace experimental
-{
-inline namespace fundamentals_v2
-{
   namespace __detail
   {
     template<typename _Container, typename _Predicate>
@@ -59,12 +54,10 @@ inline namespace fundamentals_v2
 	}
       }
   } // namespace __detail
-} // inline namespace fundamentals_v2
-} // namespace experimental
 
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace std
 
 #endif // C++14
 
-#endif // _GLIBCXX_EXPERIMENTAL_ERASE_IF_H
+#endif // _GLIBCXX_ERASE_IF_H
diff --git a/libstdc++-v3/include/experimental/map b/libstdc++-v3/include/experimental/map
index 5bd19e9bebf..1e236e535c2 100644
--- a/libstdc++-v3/include/experimental/map
+++ b/libstdc++-v3/include/experimental/map
@@ -34,7 +34,7 @@
 #if __cplusplus >= 201402L
 
 #include <map>
-#include <experimental/bits/erase_if.h>
+#include <bits/erase_if.h>
 #include <experimental/memory_resource>
 
 namespace std _GLIBCXX_VISIBILITY(default)
@@ -49,13 +49,13 @@ inline namespace fundamentals_v2
 	   typename _Predicate>
     inline void
     erase_if(map<_Key, _Tp, _Compare, _Alloc>& __cont, _Predicate __pred)
-    { __detail::__erase_nodes_if(__cont, __pred); }
+    { std::__detail::__erase_nodes_if(__cont, __pred); }
 
   template<typename _Key, typename _Tp, typename _Compare, typename _Alloc,
 	   typename _Predicate>
     inline void
     erase_if(multimap<_Key, _Tp, _Compare, _Alloc>& __cont, _Predicate __pred)
-    { __detail::__erase_nodes_if(__cont, __pred); }
+    { std::__detail::__erase_nodes_if(__cont, __pred); }
 
   namespace pmr {
     template<typename _Key, typename _Tp, typename _Compare = less<_Key>>
diff --git a/libstdc++-v3/include/experimental/set b/libstdc++-v3/include/experimental/set
index 7c90ee195e5..4a3fae6d195 100644
--- a/libstdc++-v3/include/experimental/set
+++ b/libstdc++-v3/include/experimental/set
@@ -34,7 +34,7 @@
 #if __cplusplus >= 201402L
 
 #include <set>
-#include <experimental/bits/erase_if.h>
+#include <bits/erase_if.h>
 #include <experimental/memory_resource>
 
 namespace std _GLIBCXX_VISIBILITY(default)
@@ -49,13 +49,13 @@ inline namespace fundamentals_v2
 	   typename _Predicate>
     inline void
     erase_if(set<_Key, _Compare, _Alloc>& __cont, _Predicate __pred)
-    { __detail::__erase_nodes_if(__cont, __pred); }
+    { std::__detail::__erase_nodes_if(__cont, __pred); }
 
   template<typename _Key, typename _Compare, typename _Alloc,
 	   typename _Predicate>
     inline void
     erase_if(multiset<_Key, _Compare, _Alloc>& __cont, _Predicate __pred)
-    { __detail::__erase_nodes_if(__cont, __pred); }
+    { std::__detail::__erase_nodes_if(__cont, __pred); }
 
   namespace pmr {
     template<typename _Key, typename _Compare = less<_Key>>
diff --git a/libstdc++-v3/include/experimental/unordered_map b/libstdc++-v3/include/experimental/unordered_map
index fdd3bf2f6fc..e1d23592425 100644
--- a/libstdc++-v3/include/experimental/unordered_map
+++ b/libstdc++-v3/include/experimental/unordered_map
@@ -34,7 +34,7 @@
 #if __cplusplus >= 201402L
 
 #include <unordered_map>
-#include <experimental/bits/erase_if.h>
+#include <bits/erase_if.h>
 #include <experimental/memory_resource>
 
 namespace std _GLIBCXX_VISIBILITY(default)
@@ -50,14 +50,14 @@ inline namespace fundamentals_v2
     inline void
     erase_if(unordered_map<_Key, _Tp, _Hash, _CPred, _Alloc>& __cont,
 	     _Predicate __pred)
-    { __detail::__erase_nodes_if(__cont, __pred); }
+    { std::__detail::__erase_nodes_if(__cont, __pred); }
 
   template<typename _Key, typename _Tp, typename _Hash, typename _CPred,
 	   typename _Alloc, typename _Predicate>
     inline void
     erase_if(unordered_multimap<_Key, _Tp, _Hash, _CPred, _Alloc>& __cont,
 	     _Predicate __pred)
-    { __detail::__erase_nodes_if(__cont, __pred); }
+    { std::__detail::__erase_nodes_if(__cont, __pred); }
 
   namespace pmr {
     template<typename _Key, typename _Tp, typename _Hash = hash<_Key>,
diff --git a/libstdc++-v3/include/experimental/unordered_set b/libstdc++-v3/include/experimental/unordered_set
index 8e4fc1b28f1..1b383691157 100644
--- a/libstdc++-v3/include/experimental/unordered_set
+++ b/libstdc++-v3/include/experimental/unordered_set
@@ -34,7 +34,7 @@
 #if __cplusplus >= 201402L
 
 #include <unordered_set>
-#include <experimental/bits/erase_if.h>
+#include <bits/erase_if.h>
 #include <experimental/memory_resource>
 
 namespace std _GLIBCXX_VISIBILITY(default)
@@ -50,14 +50,14 @@ inline namespace fundamentals_v2
     inline void
     erase_if(unordered_set<_Key, _Hash, _CPred, _Alloc>& __cont,
 	     _Predicate __pred)
-    { __detail::__erase_nodes_if(__cont, __pred); }
+    { std::__detail::__erase_nodes_if(__cont, __pred); }
 
   template<typename _Key, typename _Hash, typename _CPred, typename _Alloc,
 	   typename _Predicate>
     inline void
     erase_if(unordered_multiset<_Key, _Hash, _CPred, _Alloc>& __cont,
 	     _Predicate __pred)
-    { __detail::__erase_nodes_if(__cont, __pred); }
+    { std::__detail::__erase_nodes_if(__cont, __pred); }
 
   namespace pmr {
     template<typename _Key, typename _Hash = hash<_Key>,
diff --git a/libstdc++-v3/include/std/deque b/libstdc++-v3/include/std/deque
index d2c75f1f078..c577e806513 100644
--- a/libstdc++-v3/include/std/deque
+++ b/libstdc++-v3/include/std/deque
@@ -87,4 +87,27 @@ _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace std
 #endif // C++17
 
+#if __cplusplus > 201703L
+namespace std _GLIBCXX_VISIBILITY(default)
+{
+_GLIBCXX_BEGIN_NAMESPACE_VERSION
+  template<typename _Tp, typename _Alloc, typename _Predicate>
+    void
+    erase_if(deque<_Tp, _Alloc>& __cont, _Predicate __pred)
+    {
+      __cont.erase(std::remove_if(__cont.begin(), __cont.end(), __pred),
+		   __cont.end());
+    }
+
+  template<typename _Tp, typename _Alloc, typename _Up>
+    void
+    erase(deque<_Tp, _Alloc>& __cont, const _Up& __value)
+    {
+      __cont.erase(std::remove(__cont.begin(), __cont.end(), __value),
+		   __cont.end());
+    }
+_GLIBCXX_END_NAMESPACE_VERSION
+} // namespace std
+#endif // C++20
+
 #endif /* _GLIBCXX_DEQUE */
diff --git a/libstdc++-v3/include/std/forward_list b/libstdc++-v3/include/std/forward_list
index 00b41354c7d..a2cc90387ad 100644
--- a/libstdc++-v3/include/std/forward_list
+++ b/libstdc++-v3/include/std/forward_list
@@ -60,6 +60,27 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace std
 #endif // C++17
+
+#if __cplusplus > 201703L
+namespace std _GLIBCXX_VISIBILITY(default)
+{
+_GLIBCXX_BEGIN_NAMESPACE_VERSION
+  template<typename _Tp, typename _Alloc, typename _Predicate>
+    inline void 
+    erase_if(forward_list<_Tp, _Alloc>& __cont, _Predicate __pred)
+    { __cont.remove_if(__pred); }
+
+  template<typename _Tp, typename _Alloc, typename _Up>
+    inline void
+    erase(forward_list<_Tp, _Alloc>& __cont, const _Up& __value)
+    {
+      using __elem_type = typename forward_list<_Tp, _Alloc>::value_type;
+      erase_if(__cont, [&](__elem_type& __elem) { return __elem == __value; });
+    }
+_GLIBCXX_END_NAMESPACE_VERSION
+} // namespace std
+#endif // C++20
+
 #endif // C++11
 
 #endif // _GLIBCXX_FORWARD_LIST
diff --git a/libstdc++-v3/include/std/list b/libstdc++-v3/include/std/list
index 555371ffb76..58ad461b666 100644
--- a/libstdc++-v3/include/std/list
+++ b/libstdc++-v3/include/std/list
@@ -84,4 +84,25 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace std
 #endif // C++17
+
+#if __cplusplus > 201703L
+namespace std _GLIBCXX_VISIBILITY(default)
+{
+_GLIBCXX_BEGIN_NAMESPACE_VERSION
+  template<typename _Tp, typename _Alloc, typename _Predicate>
+    inline void
+    erase_if(list<_Tp, _Alloc>& __cont, _Predicate __pred)
+    { __cont.remove_if(__pred); }
+
+  template<typename _Tp, typename _Alloc, typename _Up>
+    inline void
+    erase(list<_Tp, _Alloc>& __cont, const _Up& __value)
+    {
+      using __elem_type = typename list<_Tp, _Alloc>::value_type;
+      erase_if(__cont, [&](__elem_type& __elem) { return __elem == __value; });
+    }
+_GLIBCXX_END_NAMESPACE_VERSION
+} // namespace std
+#endif // C++20
+
 #endif /* _GLIBCXX_LIST */
diff --git a/libstdc++-v3/include/std/map b/libstdc++-v3/include/std/map
index 84f8cdb701d..26b2f0ed08a 100644
--- a/libstdc++-v3/include/std/map
+++ b/libstdc++-v3/include/std/map
@@ -61,6 +61,7 @@
 #include <bits/stl_map.h>
 #include <bits/stl_multimap.h>
 #include <bits/range_access.h>
+#include <bits/erase_if.h>
 
 #ifdef _GLIBCXX_DEBUG
 # include <debug/map>
@@ -90,4 +91,23 @@ _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace std
 #endif // C++17
 
+#if __cplusplus > 201703L
+namespace std _GLIBCXX_VISIBILITY(default)
+{
+_GLIBCXX_BEGIN_NAMESPACE_VERSION
+  template<typename _Key, typename _Tp, typename _Compare, typename _Alloc,
+	   typename _Predicate>
+    inline void
+    erase_if(map<_Key, _Tp, _Compare, _Alloc>& __cont, _Predicate __pred)
+    { __detail::__erase_nodes_if(__cont, __pred); }
+
+  template<typename _Key, typename _Tp, typename _Compare, typename _Alloc,
+	   typename _Predicate>
+    inline void
+    erase_if(multimap<_Key, _Tp, _Compare, _Alloc>& __cont, _Predicate __pred)
+    { __detail::__erase_nodes_if(__cont, __pred); }
+_GLIBCXX_END_NAMESPACE_VERSION
+} // namespace std
+#endif // C++20
+
 #endif /* _GLIBCXX_MAP */
diff --git a/libstdc++-v3/include/std/set b/libstdc++-v3/include/std/set
index dd41b2f1911..432af90978d 100644
--- a/libstdc++-v3/include/std/set
+++ b/libstdc++-v3/include/std/set
@@ -61,6 +61,7 @@
 #include <bits/stl_set.h>
 #include <bits/stl_multiset.h>
 #include <bits/range_access.h>
+#include <bits/erase_if.h>
 
 #ifdef _GLIBCXX_DEBUG
 # include <debug/set>
@@ -86,4 +87,23 @@ _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace std
 #endif // C++17
 
+#if __cplusplus > 201703L
+namespace std _GLIBCXX_VISIBILITY(default)
+{
+_GLIBCXX_BEGIN_NAMESPACE_VERSION
+  template<typename _Key, typename _Compare, typename _Alloc,
+	   typename _Predicate>
+    inline void
+    erase_if(set<_Key, _Compare, _Alloc>& __cont, _Predicate __pred)
+    { __detail::__erase_nodes_if(__cont, __pred); }
+
+  template<typename _Key, typename _Compare, typename _Alloc,
+	   typename _Predicate>
+    inline void
+    erase_if(multiset<_Key, _Compare, _Alloc>& __cont, _Predicate __pred)
+    { __detail::__erase_nodes_if(__cont, __pred); }
+_GLIBCXX_END_NAMESPACE_VERSION
+} // namespace std
+#endif // C++20
+
 #endif /* _GLIBCXX_SET */
diff --git a/libstdc++-v3/include/std/string b/libstdc++-v3/include/std/string
index dd60df2ba6e..e1497bd2141 100644
--- a/libstdc++-v3/include/std/string
+++ b/libstdc++-v3/include/std/string
@@ -51,6 +51,7 @@
 #include <bits/range_access.h>
 #include <bits/basic_string.h>
 #include <bits/basic_string.tcc>
+#include <algorithm> // For remove and remove_if
 
 #if __cplusplus >= 201703L && _GLIBCXX_USE_CXX11_ABI
 namespace std _GLIBCXX_VISIBILITY(default)
@@ -72,4 +73,28 @@ _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace std
 #endif // C++17
 
+#if __cplusplus > 201703L
+namespace std _GLIBCXX_VISIBILITY(default)
+{
+_GLIBCXX_BEGIN_NAMESPACE_VERSION
+  template<typename _CharT, typename _Traits, typename _Alloc,
+	   typename _Predicate>
+    inline void
+    erase_if(basic_string<_CharT, _Traits, _Alloc>& __cont, _Predicate __pred)
+    {
+      __cont.erase(std::remove_if(__cont.begin(), __cont.end(), __pred),
+		   __cont.end());
+    }
+
+  template<typename _CharT, typename _Traits, typename _Alloc, typename _Up>
+    inline void
+    erase(basic_string<_CharT, _Traits, _Alloc>& __cont, const _Up& __value)
+    {
+      __cont.erase(std::remove(__cont.begin(), __cont.end(), __value),
+		   __cont.end());
+    }
+_GLIBCXX_END_NAMESPACE_VERSION
+} // namespace std
+#endif // C++20
+
 #endif /* _GLIBCXX_STRING */
diff --git a/libstdc++-v3/include/std/unordered_map b/libstdc++-v3/include/std/unordered_map
index fc1b1e3c71c..8cb82144fd2 100644
--- a/libstdc++-v3/include/std/unordered_map
+++ b/libstdc++-v3/include/std/unordered_map
@@ -46,6 +46,7 @@
 #include <bits/hashtable.h>
 #include <bits/unordered_map.h>
 #include <bits/range_access.h>
+#include <bits/erase_if.h>
 
 #ifdef _GLIBCXX_DEBUG
 # include <debug/unordered_map>
@@ -76,6 +77,28 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace std
 #endif // C++17
+
+#if __cplusplus > 201703L
+namespace std _GLIBCXX_VISIBILITY(default)
+{
+_GLIBCXX_BEGIN_NAMESPACE_VERSION
+  template<typename _Key, typename _Tp, typename _Hash, typename _CPred,
+	   typename _Alloc, typename _Predicate>
+    inline void
+    erase_if(unordered_map<_Key, _Tp, _Hash, _CPred, _Alloc>& __cont,
+	     _Predicate __pred)
+    { __detail::__erase_nodes_if(__cont, __pred); }
+
+  template<typename _Key, typename _Tp, typename _Hash, typename _CPred,
+	   typename _Alloc, typename _Predicate>
+    inline void
+    erase_if(unordered_multimap<_Key, _Tp, _Hash, _CPred, _Alloc>& __cont,
+	     _Predicate __pred)
+    { __detail::__erase_nodes_if(__cont, __pred); }
+_GLIBCXX_END_NAMESPACE_VERSION
+} // namespace std
+#endif // C++20
+
 #endif // C++11
 
 #endif // _GLIBCXX_UNORDERED_MAP
diff --git a/libstdc++-v3/include/std/unordered_set b/libstdc++-v3/include/std/unordered_set
index 8c04669a46e..310827528a6 100644
--- a/libstdc++-v3/include/std/unordered_set
+++ b/libstdc++-v3/include/std/unordered_set
@@ -46,6 +46,7 @@
 #include <bits/hashtable.h>
 #include <bits/unordered_set.h>
 #include <bits/range_access.h>
+#include <bits/erase_if.h>
 
 #ifdef _GLIBCXX_DEBUG
 # include <debug/unordered_set>
@@ -76,6 +77,15 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace std
 #endif // C++17
+
+#if __cplusplus > 201703L
+namespace std _GLIBCXX_VISIBILITY(default)
+{
+_GLIBCXX_BEGIN_NAMESPACE_VERSION
+_GLIBCXX_END_NAMESPACE_VERSION
+} // namespace std
+#endif // C++20
+
 #endif // C++11
 
 #endif // _GLIBCXX_UNORDERED_SET
diff --git a/libstdc++-v3/include/std/vector b/libstdc++-v3/include/std/vector
index 2a421c631f1..5a1edaf9d74 100644
--- a/libstdc++-v3/include/std/vector
+++ b/libstdc++-v3/include/std/vector
@@ -90,4 +90,27 @@ _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace std
 #endif // C++17
 
+#if __cplusplus > 201703L
+namespace std _GLIBCXX_VISIBILITY(default)
+{
+_GLIBCXX_BEGIN_NAMESPACE_VERSION
+  template<typename _Tp, typename _Alloc, typename _Predicate>
+    inline void
+    erase_if(vector<_Tp, _Alloc>& __cont, _Predicate __pred)
+    {
+      __cont.erase(std::remove_if(__cont.begin(), __cont.end(), __pred),
+		   __cont.end());
+    }
+
+  template<typename _Tp, typename _Alloc, typename _Up>
+    inline void
+    erase(vector<_Tp, _Alloc>& __cont, const _Up& __value)
+    {
+      __cont.erase(std::remove(__cont.begin(), __cont.end(), __value),
+		   __cont.end());
+    }
+_GLIBCXX_END_NAMESPACE_VERSION
+} // namespace std
+#endif // C++20
+
 #endif /* _GLIBCXX_VECTOR */
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/erasure.cc b/libstdc++-v3/testsuite/21_strings/basic_string/erasure.cc
new file mode 100644
index 00000000000..e9cca6f4158
--- /dev/null
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/erasure.cc
@@ -0,0 +1,53 @@
+// { dg-do run { target c++2a } }
+
+// Copyright (C) 2018 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/>.
+
+#include <string>
+#include <testsuite_hooks.h>
+
+void
+test01()
+{
+  auto is_vowel = [](const char c)
+  {
+    return c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u';
+  };
+
+  std::string str("cute fluffy kittens");
+  std::erase_if(str, is_vowel);
+  VERIFY( str == "ct flffy kttns" );
+}
+
+void
+test02()
+{
+  std::string str = "cute fluffy kittens";
+  std::erase(str, 'f');
+  VERIFY( str == "cute luy kittens" );
+  std::erase(str, 'z');
+  VERIFY( str == "cute luy kittens" );
+}
+
+int
+main()
+{
+  test01();
+  test02();
+
+  return 0;
+}
diff --git a/libstdc++-v3/testsuite/23_containers/deque/erasure.cc b/libstdc++-v3/testsuite/23_containers/deque/erasure.cc
new file mode 100644
index 00000000000..1fe6273c984
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/deque/erasure.cc
@@ -0,0 +1,52 @@
+// { dg-do run { target c++2a } }
+
+// Copyright (C) 2018 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/>.
+
+#include <deque>
+#include <testsuite_hooks.h>
+
+void
+test01()
+{
+  auto is_odd = [](const int i) { return i % 2 != 0; };
+
+  std::deque<int> d{ 10, 11, 12, 14, 15, 17, 18, 19 };
+  std::erase_if(d, is_odd);
+  std::deque<int> t{ 10, 12, 14, 18 };
+  VERIFY( d == t );
+}
+
+void
+test02()
+{
+  std::deque<int> d{ 10, 11, 12, 14, 15, 17, 18, 19 };
+  std::erase(d, 14);
+  std::deque<int> t{ 10, 11, 12, 15, 17, 18, 19 };
+  VERIFY( d == t );
+  std::erase(d, 20);
+  VERIFY( d == t );
+}
+
+int
+main()
+{
+  test01();
+  test02();
+
+  return 0;
+}
diff --git a/libstdc++-v3/testsuite/23_containers/forward_list/erasure.cc b/libstdc++-v3/testsuite/23_containers/forward_list/erasure.cc
new file mode 100644
index 00000000000..ac8a37d19d6
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/forward_list/erasure.cc
@@ -0,0 +1,52 @@
+// { dg-do run { target c++2a } }
+
+// Copyright (C) 2018 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/>.
+
+#include <forward_list>
+#include <testsuite_hooks.h>
+
+void
+test01()
+{
+  auto is_odd = [](const int i) { return i % 2 != 0; };
+
+  std::forward_list<int> fl{ 10, 11, 12, 14, 15, 17, 18, 19 };
+  std::erase_if(fl, is_odd);
+  std::forward_list<int> t{ 10, 12, 14, 18 };
+  VERIFY( fl == t );
+}
+
+void
+test02()
+{
+  std::forward_list<int> fl{ 10, 11, 12, 14, 15, 17, 18, 19 };
+  std::erase(fl, 14);
+  std::forward_list<int> t{ 10, 11, 12, 15, 17, 18, 19 };
+  VERIFY( fl == t );
+  std::erase(fl, 20);
+  VERIFY( fl == t );
+}
+
+int
+main()
+{
+  test01();
+  test02();
+
+  return 0;
+}
diff --git a/libstdc++-v3/testsuite/23_containers/list/erasure.cc b/libstdc++-v3/testsuite/23_containers/list/erasure.cc
new file mode 100644
index 00000000000..c8d6f2212cc
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/list/erasure.cc
@@ -0,0 +1,52 @@
+// { dg-do run { target c++2a } }
+
+// Copyright (C) 2018 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/>.
+
+#include <list>
+#include <testsuite_hooks.h>
+
+void
+test01()
+{
+  auto is_odd = [](const int i) { return i % 2 != 0; };
+
+  std::list<int> l{ 10, 11, 12, 14, 15, 17, 18, 19 };
+  std::erase_if(l, is_odd);
+  std::list<int> t{ 10, 12, 14, 18 };
+  VERIFY( l == t );
+}
+
+void
+test02()
+{
+  std::list<int> l{ 0, 11, 0, 0, 22, 33, 0, 0, 44, 0 };
+  std::erase(l, 0);
+  std::list<int> t{ 11, 22, 33, 44 };
+  VERIFY( l == t );
+  std::erase(l, 55);
+  VERIFY( l == t );
+}
+
+int
+main()
+{
+  test01();
+  test02();
+
+  return 0;
+}
diff --git a/libstdc++-v3/testsuite/23_containers/map/erasure.cc b/libstdc++-v3/testsuite/23_containers/map/erasure.cc
new file mode 100644
index 00000000000..d638715e75a
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/map/erasure.cc
@@ -0,0 +1,61 @@
+// { dg-do run { target c++2a } }
+
+// Copyright (C) 2018 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/>.
+
+#include <map>
+#include <testsuite_hooks.h>
+
+auto is_odd_pair = [](const std::pair<const int, std::string>& p)
+{
+  return p.first % 2 != 0;
+};
+
+void
+test01()
+{
+  std::map<int, std::string> m{ { 10, "A" }, { 11, "B" },
+				{ 12, "C" }, { 14, "D" },
+				{ 15, "E" }, { 17, "F" },
+				{ 18, "G" }, { 19, "H" } };
+  std::erase_if(m, is_odd_pair);
+  std::map<int, std::string> t{ { 10, "A" }, { 12, "C" },
+				{ 14, "D" }, { 18, "G" } };
+  VERIFY( m == t );
+}
+
+void
+test02()
+{
+  std::multimap<int, std::string> mm{ { 20, "S" }, { 21, "T" },
+				      { 22, "U" }, { 22, "V" },
+				      { 23, "W" }, { 23, "X" },
+				      { 24, "Y" }, { 25, "Z" } };
+  std::erase_if(mm, is_odd_pair);
+  std::multimap<int, std::string> t{ { 20, "S" }, { 22, "U" },
+				     { 22, "V" }, { 24, "Y" } };
+  VERIFY( mm == t );
+}
+
+int
+main()
+{
+  test01();
+  test02();
+
+  return 0;
+}
diff --git a/libstdc++-v3/testsuite/23_containers/set/erasure.cc b/libstdc++-v3/testsuite/23_containers/set/erasure.cc
new file mode 100644
index 00000000000..54b821b145d
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/set/erasure.cc
@@ -0,0 +1,50 @@
+// { dg-do run { target c++2a } }
+
+// Copyright (C) 2018 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/>.
+
+#include <set>
+#include <testsuite_hooks.h>
+
+auto is_odd = [](const int i) { return i % 2 != 0; };
+
+void
+test01()
+{
+  std::set<int> s{ 10, 11, 12, 14, 15, 17, 18, 19 };
+  std::erase_if(s, is_odd);
+  std::set<int> t{ 10, 12, 14, 18 };
+  VERIFY( s == t );
+}
+
+void
+test02()
+{
+  std::multiset<int> ms{ 20, 21, 22, 22, 23, 23, 24, 25 };
+  std::erase_if(ms, is_odd);
+  std::multiset<int> t{ 20, 22, 22, 24 };
+  VERIFY( ms == t );
+}
+
+int
+main()
+{
+  test01();
+  test02();
+
+  return 0;
+}
diff --git a/libstdc++-v3/testsuite/23_containers/unordered_map/erasure.cc b/libstdc++-v3/testsuite/23_containers/unordered_map/erasure.cc
new file mode 100644
index 00000000000..0e17b4e2be2
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/unordered_map/erasure.cc
@@ -0,0 +1,61 @@
+// { dg-do run { target c++2a } }
+
+// Copyright (C) 2018 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/>.
+
+#include <unordered_map>
+#include <testsuite_hooks.h>
+
+auto is_odd_pair = [](const std::pair<const int, std::string>& p)
+{
+  return p.first % 2 != 0;
+};
+
+void
+test01()
+{
+  std::unordered_map<int, std::string> um{ { 10, "A" }, { 11, "B" },
+					   { 12, "C" }, { 14, "D" },
+					   { 15, "E" }, { 17, "F" },
+					   { 18, "G" }, { 19, "H" } };
+  std::erase_if(um, is_odd_pair);
+  std::unordered_map<int, std::string> t{ { 10, "A" }, { 12, "C" },
+					  { 14, "D" }, { 18, "G" } };
+  VERIFY( um == t );
+}
+
+void
+test02()
+{
+  std::unordered_multimap<int, std::string> umm{ { 20, "S" }, { 21, "T" },
+						 { 22, "U" }, { 22, "V" },
+						 { 23, "W" }, { 23, "X" },
+						 { 24, "Y" }, { 25, "Z" } };
+  std::erase_if(umm, is_odd_pair);
+  std::unordered_multimap<int, std::string> t{ { 20, "S" }, { 22, "U" },
+					       { 22, "V" }, { 24, "Y" } };
+  VERIFY( umm == t );
+}
+
+int
+main()
+{
+  test01();
+  test02();
+
+  return 0;
+}
diff --git a/libstdc++-v3/testsuite/23_containers/unordered_set/erasure.cc b/libstdc++-v3/testsuite/23_containers/unordered_set/erasure.cc
new file mode 100644
index 00000000000..5d32c3235c3
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/unordered_set/erasure.cc
@@ -0,0 +1,52 @@
+// { dg-do run { target c++2a } }
+
+// Copyright (C) 2018 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/>.
+
+#include <unordered_set>
+#include <testsuite_hooks.h>
+
+void
+test01()
+{
+  auto is_odd = [](const int i) { return i % 2 != 0; };
+
+  std::unordered_set<int> us{ 10, 11, 12, 14, 15, 17, 18, 19 };
+  std::erase_if(us, is_odd);
+  std::unordered_set<int> t{ 10, 12, 14, 18 };
+  VERIFY( us == t );
+}
+
+void
+test02()
+{
+  auto is_odd = [](const int i) { return i % 2 != 0; };
+
+  std::unordered_multiset<int> ums{ 20, 21, 22, 22, 23, 23, 24, 25 };
+  std::erase_if(ums, is_odd);
+  std::unordered_multiset<int> t{ 20, 22, 22, 24 };
+  VERIFY( ums == t );
+}
+
+int
+main()
+{
+  test01();
+  test02();
+
+  return 0;
+}
diff --git a/libstdc++-v3/testsuite/23_containers/vector/erasure.cc b/libstdc++-v3/testsuite/23_containers/vector/erasure.cc
new file mode 100644
index 00000000000..b050b5422e8
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/vector/erasure.cc
@@ -0,0 +1,52 @@
+// { dg-do run { target c++2a } }
+
+// Copyright (C) 2018 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/>.
+
+#include <vector>
+#include <testsuite_hooks.h>
+
+void
+test01()
+{
+  auto is_odd = [](const int i) { return i % 2 != 0; };
+
+  std::vector<int> v{ 10, 11, 12, 14, 15, 17, 18, 19 };
+  std::erase_if(v, is_odd);
+  std::vector<int> t{ 10, 12, 14, 18 };
+  VERIFY( v == t );
+}
+
+void
+test02()
+{
+  std::vector<int> v{ 0, 11, 0, 0, 22, 33, 0, 0, 44, 0 };
+  std::erase(v, 0);
+  std::vector<int> t{ 11, 22, 33, 44 };
+  VERIFY( v == t );
+  std::erase(v, 55);
+  VERIFY( v == t );
+}
+
+int
+main()
+{
+  test01();
+  test02();
+
+  return 0;
+}