Added a BOOST_DEPRECATED macro for deprecated symbol markup.

BOOST_DEPRECATED can be used to mark functions, types and objects as
deprecated, with a message with a recommendation of replacement. Using
such marked symbols in code will generate compiler warnings, with the
specified message, if possible.

The warnings can be suppressed if BOOST_ALLOW_DEPRECATED_SYMBOLS is defined.
Additionally, added support BOOST_ALLOW_DEPRECATED macro that not only
allows for deprecated symbols but also deprecated headers (i.e. defining
BOOST_ALLOW_DEPRECATED is equivalent to defining both
BOOST_ALLOW_DEPRECATED_SYMBOLS and BOOST_ALLOW_DEPRECATED_HEADERS).

doc/macro_reference.qbk

@@ -1199,41 +1199,41 @@ struct foo{
 Normally evaluates to nothing, but evaluates to return x; if the compiler
 requires a return, even when it can never be reached.
 ]]
-[[`BOOST_FALLTHROUGH`][ 
-The BOOST_FALLTHROUGH macro can be used to annotate implicit fall-through 
-between switch labels: 
-`` 
- switch (x) { 
- case 40: 
- case 41: 
-    if (truth_is_out_there) { 
-       ++x; 
-       BOOST_FALLTHROUGH;  // Use instead of/along with annotations in 
-       // comments. 
-    } else { 
-      return x; 
-    } 
-    case 42: 
-       ... 
-`` 
-As shown in the example above, the BOOST_FALLTHROUGH macro should be 
-followed by a semicolon. It is designed to mimic control-flow statements 
-like 'break;', so it can be placed in most places where 'break;' can, but 
-only if there are no statements on the execution path between it and the 
-next switch label. 
+[[`BOOST_FALLTHROUGH`][
+The BOOST_FALLTHROUGH macro can be used to annotate implicit fall-through
+between switch labels:
+``
+ switch (x) {
+ case 40:
+ case 41:
+    if (truth_is_out_there) {
+       ++x;
+       BOOST_FALLTHROUGH;  // Use instead of/along with annotations in
+       // comments.
+    } else {
+      return x;
+    }
+    case 42:
+       ...
+``
+As shown in the example above, the BOOST_FALLTHROUGH macro should be
+followed by a semicolon. It is designed to mimic control-flow statements
+like 'break;', so it can be placed in most places where 'break;' can, but
+only if there are no statements on the execution path between it and the
+next switch label.
 
-When compiled with Clang >3.2 in C++11 mode, the BOOST_FALLTHROUGH macro is 
-expanded to `[[clang::fallthrough]]` attribute, which is analysed when 
-performing switch labels fall-through diagnostic ('-Wimplicit-fallthrough'). 
-See clang [@http://clang.llvm.org/docs/LanguageExtensions.html#clang__fallthrough 
-documentation on language extensions for details.] 
+When compiled with Clang >3.2 in C++11 mode, the BOOST_FALLTHROUGH macro is
+expanded to `[[clang::fallthrough]]` attribute, which is analysed when
+performing switch labels fall-through diagnostic ('-Wimplicit-fallthrough').
+See clang [@http://clang.llvm.org/docs/LanguageExtensions.html#clang__fallthrough
+documentation on language extensions for details.]
 
-When used with unsupported compilers, the BOOST_FALLTHROUGH macro has no 
-effect on diagnostics. 
+When used with unsupported compilers, the BOOST_FALLTHROUGH macro has no
+effect on diagnostics.
 
-In either case this macro has no effect on runtime behavior and performance 
-of code. 
-]] 
+In either case this macro has no effect on runtime behavior and performance
+of code.
+]]
 [[`BOOST_EXPLICIT_TEMPLATE_TYPE(t)`
 
   `BOOST_EXPLICIT_TEMPLATE_NON_TYPE(t,v)`
@@ -1405,11 +1405,11 @@ Usage example:
     handle_error("ptr is NULL");
 ``
 ]]
-[[`BOOST_ATTRIBUTE_UNUSED`][Expands to `__attribute__((unused))` when this is available - 
+[[`BOOST_ATTRIBUTE_UNUSED`][Expands to `__attribute__((unused))` when this is available -
 can be used to disable compiler warnings relating to unused types or variables.]]
-[[`BOOST_ATTRIBUTE_NODISCARD`][Expands to `[[nodiscard]]` when this is available - 
+[[`BOOST_ATTRIBUTE_NODISCARD`][Expands to `[[nodiscard]]` when this is available -
 can be used to create a warning when a type or variable is unused.]]
-[[`BOOST_ATTRIBUTE_NO_UNIQUE_ADDRESS`][Expands to `[[no_unique_address]]` when this is available - 
+[[`BOOST_ATTRIBUTE_NO_UNIQUE_ADDRESS`][Expands to `[[no_unique_address]]` when this is available -
 can be used to indicate that a non-static data member need not have a unique address (for example empty classes).]]
 [[`BOOST_MAY_ALIAS`, `BOOST_NO_MAY_ALIAS`][
 `BOOST_MAY_ALIAS` expands to a type attribute that can be used to mark types that may
@@ -1423,6 +1423,27 @@ Usage example:
   typedef unsigned int BOOST_MAY_ALIAS aliasing_uint;
 ``
 ]]
+[[`BOOST_DEPRECATED(M)`][Expands to an attribute for a symbol that generates warnings when that
+symbol is used in code. The warnings may contain a message `M`, which must be a string literal.
+This attribute may be applied to types, functions or objects and is typically used to mark
+parts of the API as deprecated with a recommendation of replacement.
+
+Example:
+``
+BOOST_DEPRECATED("Use bar() instead.")
+void foo();
+
+template< typename T >
+class BOOST_DEPRECATED("Use std::unique_ptr instead.") auto_ptr
+{
+};
+
+BOOST_DEPRECATED("Use std::numeric_limits<int>::max() instead.")
+const int max_int = 0x7fffffff;
+``
+
+The warnings issued by `BOOST_DEPRECATED` can be suppressed by defining
+`BOOST_ALLOW_DEPRECATED_SYMBOLS` or `BOOST_ALLOW_DEPRECATED` macros.]]
 [[`BOOST_PRAGMA_MESSAGE(M)`][Defined in header `<boost/config/pragma_message.hpp>`,
 this macro expands to the equivalent of `#pragma message(M)`. `M` must be a string
 literal.
@@ -1438,8 +1459,8 @@ this macro issues the message "This header is deprecated. Use `A` instead." via
 
 Example: `BOOST_HEADER_DEPRECATED("<boost/config/workaround.hpp>")`
 
-The messages issued by `BOOST_HEADER_DEPRECATED` can be suppressed by defining the macro
-`BOOST_ALLOW_DEPRECATED_HEADERS`.]]
+The messages issued by `BOOST_HEADER_DEPRECATED` can be suppressed by defining
+`BOOST_ALLOW_DEPRECATED_HEADERS` or `BOOST_ALLOW_DEPRECATED` macros.]]
 ]
 
 [endsect]

include/boost/config/compiler/clang.hpp

@@ -325,11 +325,18 @@
 // All versions with __cplusplus above this value seem to support this:
 #  define BOOST_NO_CXX14_DIGIT_SEPARATORS
 #endif
-//
-// __builtin_unreachable:
-#if defined(__has_builtin) && __has_builtin(__builtin_unreachable)
+
+// Unreachable code markup
+#if defined(__has_builtin)
+#if __has_builtin(__builtin_unreachable)
 #define BOOST_UNREACHABLE_RETURN(x) __builtin_unreachable();
 #endif
+#endif
+
+// Deprecated symbol markup
+#if __has_attribute(deprecated)
+#define BOOST_DEPRECATED(msg) __attribute__((deprecated(msg)))
+#endif
 
 #if (__clang_major__ == 3) && (__clang_minor__ == 0)
 // Apparently a clang bug:

include/boost/config/compiler/gcc.hpp

@@ -340,12 +340,18 @@
 // Type aliasing hint. Supported since gcc 3.3.
 #define BOOST_MAY_ALIAS __attribute__((__may_alias__))
 
-//
-// __builtin_unreachable:
+// Unreachable code markup
 #if BOOST_GCC_VERSION >= 40500
 #define BOOST_UNREACHABLE_RETURN(x) __builtin_unreachable();
 #endif
 
+// Deprecated symbol markup
+#if BOOST_GCC_VERSION >= 40500
+#define BOOST_DEPRECATED(msg) __attribute__((deprecated(msg)))
+#else
+#define BOOST_DEPRECATED(msg) __attribute__((deprecated))
+#endif
+
 #ifndef BOOST_COMPILER
 #  define BOOST_COMPILER "GNU C++ version " __VERSION__
 #endif
@@ -359,7 +365,7 @@
 
 // versions check:
 // we don't know gcc prior to version 3.30:
-#if (BOOST_GCC_VERSION< 30300)
+#if (BOOST_GCC_VERSION < 30300)
 #  error "Compiler not configured - please reconfigure"
 #endif
 //

include/boost/config/compiler/sunpro_cc.hpp

@@ -86,6 +86,12 @@
 #  define BOOST_SYMBOL_VISIBLE __global
 #endif
 
+// Deprecated symbol markup
+// Oracle Studio 12.4 supports deprecated attribute with a message; this is the first release that supports the attribute.
+#if (__SUNPRO_CC >= 0x5130)
+#define BOOST_DEPRECATED(msg) __attribute__((deprecated(msg)))
+#endif
+
 #if (__SUNPRO_CC < 0x5130)
 // C++03 features in 12.4:
 #define BOOST_NO_TWO_PHASE_NAME_LOOKUP

include/boost/config/compiler/visualc.hpp

@@ -107,6 +107,14 @@
 #  define BOOST_NO_RTTI
 #endif
 
+// Deprecated symbol markup
+#if (_MSC_VER >= 1400)
+#define BOOST_DEPRECATED(msg) __declspec(deprecated(msg))
+#else
+// MSVC 7.1 only supports the attribute without a message
+#define BOOST_DEPRECATED(msg) __declspec(deprecated)
+#endif
+
 //
 // TR1 features:
 //

include/boost/config/compiler/xlcpp.hpp

@@ -270,6 +270,10 @@
 #  define BOOST_NO_CXX14_DIGIT_SEPARATORS
 #endif
 
+// Deprecated symbol markup
+#if __has_attribute(deprecated)
+#define BOOST_DEPRECATED(msg) __attribute__((deprecated(msg)))
+#endif
 
 // Unused attribute:
 #if defined(__GNUC__) && (__GNUC__ >= 4)

include/boost/config/detail/suffix.hpp

@@ -668,6 +668,23 @@ namespace std{ using ::type_info; }
 #  define BOOST_NORETURN
 #endif
 
+// BOOST_DEPRECATED -------------------------------------------//
+// The macro can be used to mark deprecated symbols, such as functions, objects and types.
+// Any code that uses these symbols will produce warnings, possibly with a message specified
+// as an argument. The warnings can be suppressed by defining BOOST_ALLOW_DEPRECATED_SYMBOLS
+// or BOOST_ALLOW_DEPRECATED.
+#if !defined(BOOST_DEPRECATED) && __cplusplus >= 201402
+#define BOOST_DEPRECATED(msg) [[deprecated(msg)]]
+#endif
+
+#if defined(BOOST_ALLOW_DEPRECATED_SYMBOLS) || defined(BOOST_ALLOW_DEPRECATED)
+#undef BOOST_DEPRECATED
+#endif
+
+#if !defined(BOOST_DEPRECATED)
+#define BOOST_DEPRECATED(msg)
+#endif
+
 // Branch prediction hints
 // These macros are intended to wrap conditional expressions that yield true or false
 //

include/boost/config/header_deprecated.hpp

@@ -17,7 +17,7 @@
 
 #include <boost/config/pragma_message.hpp>
 
-#if defined(BOOST_ALLOW_DEPRECATED_HEADERS)
+#if defined(BOOST_ALLOW_DEPRECATED_HEADERS) || defined(BOOST_ALLOW_DEPRECATED)
 # define BOOST_HEADER_DEPRECATED(a)
 #else
 # define BOOST_HEADER_DEPRECATED(a) BOOST_PRAGMA_MESSAGE("This header is deprecated. Use " a " instead.")

test/Jamfile.v2

@@ -84,9 +84,9 @@ test-suite config
      [ run config_info.cpp : : : <test-info>always_show_run_output <threading>single <toolset>msvc:<runtime-link>static <toolset>msvc:<link>static <toolset>msvc:<warnings-as-errors>on <toolset>gcc:<warnings-as-errors>on <toolset>clang:<warnings-as-errors>on ]
      [ run config_info.cpp : : : <test-info>always_show_run_output <threading>multi <toolset>msvc:<warnings-as-errors>on <toolset>gcc:<warnings-as-errors>on <toolset>clang:<warnings-as-errors>on : config_info_threaded ]
      [ run config_info.cpp : : : <test-info>always_show_run_output <rtti>off <toolset>msvc:<warnings-as-errors>on <toolset>gcc:<warnings-as-errors>on <toolset>clang:<warnings-as-errors>on : config_info_no_rtti ]
-     [ run config_info.cpp : : : <test-info>always_show_run_output <exception-handling>off 
-     		<target-os>vxworks:<build>no      
-     		: config_info_no_except ]
+     [ run config_info.cpp : : : <test-info>always_show_run_output <exception-handling>off
+          <target-os>vxworks:<build>no
+          : config_info_no_except ]
      [ run math_info.cpp : : : <test-info>always_show_run_output <toolset>borland:<runtime-link>static <toolset>borland:<link>static ]
      [ run abi/abi_test.cpp abi/main.cpp ]
      [ run limits_test.cpp ]
@@ -113,11 +113,12 @@ test-suite config
     [ run helper_macros_test.cpp ]
     [ compile pragma_message_test.cpp ]
     [ compile header_deprecated_test.cpp ]
+    [ compile symbol_deprecated_test.cpp ]
     [ compile boost_override_test.cpp ]
   ;
 
 obj has_clang_implicit_fallthrough : cmd_line_check.cpp :
-		<toolset>clang:<cxxflags>"-std=c++11 -Wimplicit-fallthrough" <warnings-as-errors>on <warnings>all ;
+    <toolset>clang:<cxxflags>"-std=c++11 -Wimplicit-fallthrough" <warnings-as-errors>on <warnings>all ;
 
 explicit has_clang_implicit_fallthrough ;
 
@@ -128,9 +129,9 @@ explicit math_info_printer ;
 
 actions print-run
 {
-      echo With Standard Version $(STANDARD:E=default)
-      echo =====================================================================
-      $(>)
+    echo With Standard Version $(STANDARD:E=default)
+    echo =====================================================================
+    $(>)
 }
 
 rule print-run ( target : sources * : properties * )
@@ -147,4 +148,3 @@ explicit print_math_info ;
 exe config_info_travis : config_info.cpp ;
 install config_info_travis_install : config_info_travis : <location>. ;
 explicit config_info_travis_install ;
-

test/symbol_deprecated_test.cpp

@@ -0,0 +1,19 @@
+//  Copyright 2022 Andrey Semashev.
+//
+//  Distributed under the Boost Software License, Version 1.0.
+//
+//  See accompanying file LICENSE_1_0.txt or copy at
+//  http://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/config.hpp>
+
+BOOST_DEPRECATED("Use bar() instead.")
+void foo();
+
+template< typename T >
+class BOOST_DEPRECATED("Use std::unique_ptr instead.") my_auto_ptr
+{
+};
+
+BOOST_DEPRECATED("Use std::numeric_limits<int>::max() instead.")
+const int max_int = 0x7fffffff;