Support use of standard placeholders with boost::bind

include/boost/bind/bind.hpp

@@ -28,6 +28,7 @@
 #include <boost/is_placeholder.hpp>
 #include <boost/bind/arg.hpp>
 #include <boost/bind/detail/result_traits.hpp>
+#include <boost/bind/std_placeholders.hpp>
 #include <boost/detail/workaround.hpp>
 #include <boost/visit_each.hpp>
 #include <boost/core/enable_if.hpp>

include/boost/bind/std_placeholders.hpp

@@ -0,0 +1,39 @@
+#ifndef BOOST_BIND_STD_PLACEHOLDERS_HPP_INCLUDED
+#define BOOST_BIND_STD_PLACEHOLDERS_HPP_INCLUDED
+
+// MS compatible compilers support #pragma once
+
+#if defined(_MSC_VER) && (_MSC_VER >= 1020)
+# pragma once
+#endif
+
+// Copyright 2021 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/is_placeholder.hpp>
+#include <boost/config.hpp>
+
+#if !defined(BOOST_NO_CXX11_HDR_FUNCTIONAL) && !defined(BOOST_NO_CXX11_DECLTYPE) && !defined(BOOST_NO_CXX11_HDR_TYPE_TRAITS)
+
+#include <functional>
+#include <type_traits>
+
+namespace boost
+{
+
+template<> struct is_placeholder< typename std::decay<decltype(std::placeholders::_1)>::type > { enum _vt { value = 1 }; };
+template<> struct is_placeholder< typename std::decay<decltype(std::placeholders::_2)>::type > { enum _vt { value = 2 }; };
+template<> struct is_placeholder< typename std::decay<decltype(std::placeholders::_3)>::type > { enum _vt { value = 3 }; };
+template<> struct is_placeholder< typename std::decay<decltype(std::placeholders::_4)>::type > { enum _vt { value = 4 }; };
+template<> struct is_placeholder< typename std::decay<decltype(std::placeholders::_5)>::type > { enum _vt { value = 5 }; };
+template<> struct is_placeholder< typename std::decay<decltype(std::placeholders::_6)>::type > { enum _vt { value = 6 }; };
+template<> struct is_placeholder< typename std::decay<decltype(std::placeholders::_7)>::type > { enum _vt { value = 7 }; };
+template<> struct is_placeholder< typename std::decay<decltype(std::placeholders::_8)>::type > { enum _vt { value = 8 }; };
+template<> struct is_placeholder< typename std::decay<decltype(std::placeholders::_9)>::type > { enum _vt { value = 9 }; };
+
+} // namespace boost
+
+#endif
+
+#endif // #ifndef BOOST_BIND_STD_PLACEHOLDERS_HPP_INCLUDED

test/Jamfile.v2

@@ -78,3 +78,4 @@ run bind_cpp20_test.cpp ;
 run protect_test2.cpp ;
 run protect_cpp20_test.cpp ;
 run bind_noexcept_mf2_test.cpp ;
+run std_placeholders_test.cpp ;

test/std_placeholders_test.cpp

@@ -0,0 +1,50 @@
+// Copyright 2021 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/bind/bind.hpp>
+#include <boost/core/lightweight_test.hpp>
+#include <functional>
+#include <boost/config.hpp>
+#include <boost/config/pragma_message.hpp>
+
+#if defined(BOOST_NO_CXX11_HDR_FUNCTIONAL)
+
+BOOST_PRAGMA_MESSAGE( "Skipping test due to BOOST_NO_CXX11_HDR_FUNCTIONAL being defined" )
+int main() {}
+
+#elif defined(BOOST_NO_CXX11_DECLTYPE)
+
+BOOST_PRAGMA_MESSAGE( "Skipping test due to BOOST_NO_CXX11_DECLTYPE being defined" )
+int main() {}
+
+#elif defined(BOOST_NO_CXX11_HDR_TYPE_TRAITS)
+
+BOOST_PRAGMA_MESSAGE( "Skipping test due to BOOST_NO_CXX11_HDR_TYPE_TRAITS being defined" )
+int main() {}
+
+#else
+
+int f( int x )
+{
+    return -x;
+}
+
+int main()
+{
+    using namespace std::placeholders;
+
+    BOOST_TEST_EQ( boost::bind( f, _1 )( 1 ), -1 );
+    BOOST_TEST_EQ( boost::bind( f, _2 )( 1, 2 ), -2 );
+    BOOST_TEST_EQ( boost::bind( f, _3 )( 1, 2, 3 ), -3 );
+    BOOST_TEST_EQ( boost::bind( f, _4 )( 1, 2, 3, 4 ), -4 );
+    BOOST_TEST_EQ( boost::bind( f, _5 )( 1, 2, 3, 4, 5 ), -5 );
+    BOOST_TEST_EQ( boost::bind( f, _6 )( 1, 2, 3, 4, 5, 6 ), -6 );
+    BOOST_TEST_EQ( boost::bind( f, _7 )( 1, 2, 3, 4, 5, 6, 7 ), -7 );
+    BOOST_TEST_EQ( boost::bind( f, _8 )( 1, 2, 3, 4, 5, 6, 7, 8 ), -8 );
+    BOOST_TEST_EQ( boost::bind( f, _9 )( 1, 2, 3, 4, 5, 6, 7, 8, 9 ), -9 );
+
+    return boost::report_errors();
+}
+
+#endif