Use C++11 language features unconditionally.

Use nullptr, rvalue references, default function template parameters,
deleted/defaulted functions, noexcept, final, override and scoped enums.

Don't use constexpr yet, as it would raise MSVC requirement.

Author: Lastique

CMakeLists.txt

@@ -75,6 +75,19 @@ endif()
 add_library(boost_filesystem ${BOOST_FILESYSTEM_SOURCES})
 add_library(Boost::filesystem ALIAS boost_filesystem)
 
+target_compile_features(boost_filesystem PUBLIC
+    cxx_rvalue_references
+    cxx_strong_enums
+    cxx_noexcept
+    cxx_nullptr
+    cxx_defaulted_functions
+    cxx_defaulted_move_initializers
+    cxx_deleted_functions
+    cxx_default_function_template_args
+    cxx_final
+    cxx_override
+)
+
 get_target_property(BOOST_FILESYSTEM_TARGET_TYPE boost_filesystem TYPE)
 if(BOOST_FILESYSTEM_TARGET_TYPE STREQUAL "SHARED_LIBRARY")
     set(CMAKE_REQUIRED_LIBRARIES "-Wl,--no-undefined")

build/Jamfile.v2

@@ -1,14 +1,15 @@
 # Boost Filesystem Library Build Jamfile
 
 # (C) Copyright Beman Dawes 2002-2006
-# (C) Copyright Andrey Semashev 2020, 2021
+# (C) Copyright Andrey Semashev 2020-2024
 # Distributed under the Boost Software License, Version 1.0.
 # See www.boost.org/LICENSE_1_0.txt
 
 # See library home page at http://www.boost.org/libs/filesystem
 
 import project ;
 import configure ;
+import config : requires ;
 
 lib bcrypt ;
 lib advapi32 ;
@@ -122,6 +123,19 @@ rule check-linkflag-no-undefined ( properties * )
     return $(result) ;
 }
 
+local cxx_requirements = [ requires
+    cxx11_rvalue_references
+    cxx11_scoped_enums
+    cxx11_noexcept
+    cxx11_nullptr
+    cxx11_defaulted_functions
+    cxx11_defaulted_moves
+    cxx11_deleted_functions
+    cxx11_function_template_default_args
+    cxx11_final
+    cxx11_override
+] ;
+
 project boost/filesystem
     : requirements
       <host-os>hpux,<toolset>gcc:<define>_INCLUDE_STDC__SOURCE_199901
@@ -188,14 +202,17 @@ rule select-platform-specific-sources ( properties * )
 }
 
 lib boost_filesystem
-    : $(SOURCES).cpp
-    : <define>BOOST_FILESYSTEM_SOURCE
+    : ## sources ##
+      $(SOURCES).cpp
+    : ## requirements ##
+      <define>BOOST_FILESYSTEM_SOURCE
       <conditional>@select-platform-specific-sources
       <include>../src
       <link>shared:<define>BOOST_FILESYSTEM_DYN_LINK=1
       <link>static:<define>BOOST_FILESYSTEM_STATIC_LINK=1
-    :
-    :
+      $(cxx_requirements)
+    : usage-requirements
+      $(cxx_requirements)
     ;
 
 boost-install boost_filesystem ;

include/boost/filesystem/cstdio.hpp

@@ -41,8 +41,8 @@ inline std::FILE* fopen(filesystem::path const& p, const char* mode)
         wchar_t buf[128u];
         wchar_t* p;
 
-        small_array() BOOST_NOEXCEPT : p(buf) {}
-        ~small_array() BOOST_NOEXCEPT
+        small_array() noexcept : p(buf) {}
+        ~small_array() noexcept
         {
             if (BOOST_UNLIKELY(p != buf))
                 std::free(p);
@@ -52,18 +52,18 @@ inline std::FILE* fopen(filesystem::path const& p, const char* mode)
     std::size_t wmode_len = std::mbstowcs(wmode.p, mode, sizeof(wmode.buf) / sizeof(wchar_t));
     if (BOOST_UNLIKELY(wmode_len >= (sizeof(wmode.buf) / sizeof(wchar_t))))
     {
-        wmode_len = std::mbstowcs(NULL, mode, 0u);
+        wmode_len = std::mbstowcs(nullptr, mode, 0u);
         // Check for size overflow, including (size_t)-1, which indicates mbstowcs error
         if (BOOST_UNLIKELY(wmode_len >= (static_cast< std::size_t >(-1) / sizeof(wchar_t))))
-            return NULL;
+            return nullptr;
 
         wmode.p = static_cast< wchar_t* >(std::malloc((wmode_len + 1u) * sizeof(wchar_t)));
         if (BOOST_UNLIKELY(!wmode.p))
-            return NULL;
+            return nullptr;
 
         std::size_t wmode_len2 = std::mbstowcs(wmode.p, mode, wmode_len + 1u);
         if (BOOST_UNLIKELY(wmode_len2 > wmode_len))
-            return NULL;
+            return nullptr;
     }
 
     return ::_wfopen(p.c_str(), wmode.p);

include/boost/filesystem/detail/path_traits.hpp

@@ -49,7 +49,7 @@ template< typename, typename, typename > class basic_string;
 
 namespace filesystem {
 
-BOOST_FILESYSTEM_DECL system::error_category const& codecvt_error_category() BOOST_NOEXCEPT;
+BOOST_FILESYSTEM_DECL system::error_category const& codecvt_error_category() noexcept;
 
 class directory_entry;
 
@@ -398,19 +398,19 @@ struct is_native_char_ptr< const path_native_char_type* > :
 };
 
 
-//! Converts character encoding using the supplied codecvt facet. If \a cvt is \c NULL then \c path::codecvt() will be used.
+//! Converts character encoding using the supplied codecvt facet. If \a cvt is \c nullptr then \c path::codecvt() will be used.
 BOOST_FILESYSTEM_DECL
-void convert(const char* from, const char* from_end, std::wstring& to, const codecvt_type* cvt = NULL);
+void convert(const char* from, const char* from_end, std::wstring& to, const codecvt_type* cvt = nullptr);
 
 //! \overload convert
 BOOST_FILESYSTEM_DECL
-void convert(const wchar_t* from, const wchar_t* from_end, std::string& to, const codecvt_type* cvt = NULL);
+void convert(const wchar_t* from, const wchar_t* from_end, std::string& to, const codecvt_type* cvt = nullptr);
 
 
 //  Source dispatch  -----------------------------------------------------------------//
 
 template< typename Source, typename Callback >
-typename Callback::result_type dispatch(Source const& source, Callback cb, const codecvt_type* cvt = NULL);
+typename Callback::result_type dispatch(Source const& source, Callback cb, const codecvt_type* cvt = nullptr);
 
 template< typename Callback >
 BOOST_FORCEINLINE typename Callback::result_type dispatch(const char* source, Callback cb, const codecvt_type* cvt, ntcts_type_tag)
@@ -442,7 +442,7 @@ BOOST_FORCEINLINE typename Callback::result_type dispatch(Source const& source,
 template< typename Callback >
 BOOST_FORCEINLINE typename Callback::result_type dispatch(std::vector< char > const& source, Callback cb, const codecvt_type* cvt, range_type_tag)
 {
-    const char* data = NULL, *data_end = NULL;
+    const char* data = nullptr, *data_end = nullptr;
     if (!source.empty())
     {
         data = &source[0];
@@ -454,7 +454,7 @@ BOOST_FORCEINLINE typename Callback::result_type dispatch(std::vector< char > co
 template< typename Callback >
 BOOST_FORCEINLINE typename Callback::result_type dispatch(std::vector< wchar_t > const& source, Callback cb, const codecvt_type* cvt, range_type_tag)
 {
-    const wchar_t* data = NULL, *data_end = NULL;
+    const wchar_t* data = nullptr, *data_end = nullptr;
     if (!source.empty())
     {
         data = &source[0];
@@ -496,9 +496,7 @@ yes_type check_convertible(std::wstring_view const&);
 #endif
 yes_type check_convertible(boost::basic_string_view< char, std::char_traits< char > > const&);
 yes_type check_convertible(boost::basic_string_view< wchar_t, std::char_traits< wchar_t > > const&);
-#if !defined(BOOST_NO_CXX11_NULLPTR)
 no_type check_convertible(std::nullptr_t);
-#endif
 no_type check_convertible(...);
 
 } // namespace is_convertible_to_path_source_impl
@@ -525,9 +523,7 @@ namespace is_convertible_to_std_string_view_impl {
 
 yes_type check_convertible(std::string_view const&);
 yes_type check_convertible(std::wstring_view const&);
-#if !defined(BOOST_NO_CXX11_NULLPTR)
 no_type check_convertible(std::nullptr_t);
-#endif
 no_type check_convertible(...);
 
 } // namespace is_convertible_to_std_string_view_impl
@@ -551,9 +547,7 @@ yes_type check_convertible(boost::container::basic_string< char, std::char_trait
 yes_type check_convertible(boost::container::basic_string< wchar_t, std::char_traits< wchar_t >, void > const&);
 yes_type check_convertible(boost::basic_string_view< char, std::char_traits< char > > const&);
 yes_type check_convertible(boost::basic_string_view< wchar_t, std::char_traits< wchar_t > > const&);
-#if !defined(BOOST_NO_CXX11_NULLPTR)
 no_type check_convertible(std::nullptr_t);
-#endif
 no_type check_convertible(...);
 
 } // namespace is_convertible_to_path_source_non_std_string_view_impl
@@ -683,7 +677,7 @@ BOOST_FORCEINLINE typename Callback::result_type dispatch_convertible_impl(std::
 #endif // !defined(BOOST_NO_CXX17_HDR_STRING_VIEW)
 
 template< typename Source, typename Callback >
-BOOST_FORCEINLINE typename Callback::result_type dispatch_convertible(Source const& source, Callback cb, const codecvt_type* cvt = NULL)
+BOOST_FORCEINLINE typename Callback::result_type dispatch_convertible(Source const& source, Callback cb, const codecvt_type* cvt = nullptr)
 {
     typedef typename boost::remove_cv< Source >::type source_t;
     return path_traits::dispatch_convertible_impl< source_t >(source, cb, cvt);
@@ -709,7 +703,7 @@ template< typename Source, typename Callback >
 BOOST_FORCEINLINE typename boost::disable_if_c<
     is_convertible_to_std_string_view< typename boost::remove_cv< Source >::type >::value,
     typename Callback::result_type
->::type dispatch_convertible(Source const& source, Callback cb, const codecvt_type* cvt = NULL)
+>::type dispatch_convertible(Source const& source, Callback cb, const codecvt_type* cvt = nullptr)
 {
     typedef typename boost::remove_cv< Source >::type source_t;
     return path_traits::dispatch_convertible_impl< source_t >(source, cb, cvt);
@@ -719,7 +713,7 @@ template< typename Source, typename Callback >
 BOOST_FORCEINLINE typename boost::enable_if_c<
     is_convertible_to_std_string_view< typename boost::remove_cv< Source >::type >::value,
     typename Callback::result_type
->::type dispatch_convertible(Source const& source, Callback cb, const codecvt_type* cvt = NULL)
+>::type dispatch_convertible(Source const& source, Callback cb, const codecvt_type* cvt = nullptr)
 {
     typedef typename boost::remove_cv< Source >::type source_t;
     return path_traits::dispatch_convertible_sv_impl< source_t >(source, cb, cvt);