Use boost::addressof and update docs

To make it clear:
       Base* base = new Base();

       static_cast<Derived*>(base)                 ===> OK
       static_cast<Derived&>(*base)                ===> OK

       boost::polymorphic_downcast<Derived*>(base)  ===> OK
       boost::polymorphic_downcast<Derived&>(*base) ===> IMPOSSIBLE

    boost::polymorphic_downcast being a kind of "debug-safe version" of
    static_cast, it should provide the same capabilities.

    This patch extend boost::polymorphic_downcast to support references just
    like static_cast does.
    This is achieved by introducing a partial specialization for references.
    Unit tests have been updated accordingly.

.travis.yml

@@ -2,118 +2,148 @@
 # subject to 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)
 #
-# Copyright Antony Polukhin 2014-2016.
+# Copyright Antony Polukhin 2014-2018.
 
 #
 # See https://svn.boost.org/trac/boost/wiki/TravisCoverals for description of this file
 # and how it can be used with Boost libraries.
 #
-# File revision #7
+# File revision #9
 
 sudo: false
 language: cpp
-compiler:
-    - gcc
-#    - clang
-
-os:
-    - linux
+os: linux
 
 env:
-    global:
-        # Autodetect Boost branch by using the following code: - BRANCH_TO_TEST=$TRAVIS_BRANCH
-        # or just directly specify it
-        - BRANCH_TO_TEST=$TRAVIS_BRANCH
+  global:
+    # Autodetect Boost branch by using the following code: - BOOST_BRANCH=$TRAVIS_BRANCH
+    # or just directly specify it
+    - BOOST_BRANCH=develop && [ "$TRAVIS_BRANCH" == "master" ] && BOOST_BRANCH=master || true
 
-        # Files, which coverage results must be ignored (files from other projects).
-        # Example: - IGNORE_COVERAGE='*/boost/progress.hpp */filesystem/src/*'
-        - IGNORE_COVERAGE=''
+    # Files, which coverage results must be ignored (files from other projects).
+    # Example: - IGNORE_COVERAGE='*/boost/progress.hpp */filesystem/src/*'
+    - IGNORE_COVERAGE=''
 
-        # Explicitly remove the following library from Boost. This may be usefull, if you're for example running Travis
-        # from `Boost.DLL` repo, while Boost already has `dll`.
-        #
-        # By default is eaual to - BOOST_REMOVE=$(basename $TRAVIS_BUILD_DIR)
-        # This will force to use local repo content, instead of the Boost's default.
-        - BOOST_REMOVE=$(basename $TRAVIS_BUILD_DIR)
+    # boost-local/libs/ folder to put this library into. This may be useful, if you're for example running Travis
+    # from `Boost.DLL` repo while Boost already has `dll` and with to replace `dll` with content of`Boost.DLL`.
+    #
+    # Otherwise just leave the default value - BOOST_LIBS_FOLDER=$(basename $TRAVIS_BUILD_DIR)
+    - BOOST_LIBS_FOLDER=$(basename $TRAVIS_BUILD_DIR)
 
-    matrix:
-        # Note that "--coverage -fsanitize=address,leak,undefined -DBOOST_TRAVISCI_BUILD" are added automatically lower in code
-        - CXX_FLAGS="-std=c++98" LINK_FLAGS="" TOOLSET=gcc-6
-        - CXX_FLAGS="-std=c++11" LINK_FLAGS="" TOOLSET=gcc-6
-        - CXX_FLAGS="-std=c++1y" LINK_FLAGS="" TOOLSET=gcc-6
-        #- CXX_FLAGS="-std=c++11 -stdlib=libc++" LINK_FLAGS="-stdlib=libc++" TOOLSET=clang
-        #- CXX_FLAGS="-std=c++1y -stdlib=libc++" LINK_FLAGS="-stdlib=libc++" TOOLSET=clang
+    # Global options for sanitizers
+    - UBSAN_OPTIONS=print_stacktrace=1
+    - LSAN_OPTIONS=verbosity=1:log_threads=1
+
+# `--coverage` flags required to generate coverage info for Coveralls
+matrix:
+  include:
+    - env: B2_ARGS='cxxstd=98,03,11,14,1z toolset=gcc-8 cxxflags="--coverage -fsanitize=address,leak,undefined -fno-sanitize-recover=undefined -DBOOST_TRAVISCI_BUILD" linkflags="--coverage  -lasan -lubsan"'
+      name: "GCC-8"
+      sudo: required # Required by leak sanitizer
+      addons:
+        apt:
+          sources: ubuntu-toolchain-r-test
+          packages: g++-8
+
+    - env: B2_ARGS='cxxstd=98,0x toolset=gcc-4.6 cxxflags="--coverage -DBOOST_TRAVISCI_BUILD" linkflags="--coverage"'
+      name: "GCC-4.6"
+      addons:
+        apt:
+          sources: ubuntu-toolchain-r-test
+          packages: g++-4.6
+
+#    - env: B2_ARGS='cxxstd=98,03,11,14,1y toolset=gcc-8 cxxflags="--coverage -fsanitize=address,leak,undefined -fno-sanitize-recover=undefined -DBOOST_TRAVISCI_BUILD -fno-exceptions" linkflags="--coverage -lasan -lubsan"'
+#      name: "GCC-8, no exceptions"
+#      sudo: required # Required by leak sanitizer
+#      addons:
+#        apt:
+#          sources: ubuntu-toolchain-r-test
+#          packages: g++-8
+
+    - env: B2_ARGS='cxxstd=98,03,11,14,1z toolset=clang-7 cxxflags="--coverage -fsanitize=address,leak,undefined -fno-sanitize-recover=undefined -DBOOST_TRAVISCI_BUILD" linkflags="--coverage -fsanitize=address,leak,undefined"'
+      name: "Clang-7"
+      sudo: required # Required by leak sanitizer
+      addons:
+        apt:
+          sources: llvm-toolchain-trusty-7
+          packages: clang++-7
+
+    - env: B2_ARGS='cxxstd=03,11,14 toolset=clang-libc++ cxxflags="--coverage -fsanitize=address,leak,undefined -fno-sanitize-recover=undefined -DBOOST_TRAVISCI_BUILD" linkflags="--coverage -fsanitize=address,leak,undefined"'
+      name: "Clang-3.8, libc++"
+      sudo: required # Required by leak sanitizer
+      addons:
+        apt:
+          packages: libc++-dev
 
 ###############################################################################################################
 # From this point and below code is same for all the Boost libs
 ###############################################################################################################
 
-
 # Installing additional tools
 addons:
   apt:
-    sources:
-    - ubuntu-toolchain-r-test
-    - git-core
+    sources: git-core
     packages:
     - git
     - python-yaml
-    - gcc-6
-    - g++-6
-    - clang
-    - libc++-dev
 
 before_install:
-    # Set this to the name of the library
-    - PROJECT_TO_TEST=`basename $TRAVIS_BUILD_DIR`
-    # Cloning Boost libraries (fast nondeep cloning)
-    - BOOST=$HOME/boost-local
-    - echo "Testing $PROJECT_TO_TEST, to remove $BOOST/libs/$BOOST_REMOVE, testing branch $BRANCH_TO_TEST"
-    - git init $BOOST
-    - cd $BOOST
-    - git remote add --no-tags -t $BRANCH_TO_TEST origin https://github.com/boostorg/boost.git
-    - git fetch --depth=1
-    - git checkout $BRANCH_TO_TEST
-    - git submodule update --jobs=3 --init --merge
-    - git remote set-branches --add origin $BRANCH_TO_TEST
-    - git pull --recurse-submodules
-    - git status
-    - rm -rf $BOOST/libs/$BOOST_REMOVE
-    - mv $TRAVIS_BUILD_DIR $BOOST/libs/$PROJECT_TO_TEST
-    - TRAVIS_BUILD_DIR=$BOOST/libs/$PROJECT_TO_TEST
-    - ./bootstrap.sh
-    - ./b2 headers
-    - cd $BOOST/libs/$PROJECT_TO_TEST/test/
+  # Cloning minimal set of Boost libraries
+  - BOOST=$HOME/boost-local
+  - git clone -b $BOOST_BRANCH --depth 1 https://github.com/boostorg/boost.git $BOOST
+  - cd $BOOST
+  - git submodule update --init --depth 1 tools/build tools/boostdep
+
+  # Replacing Boost module with this project and installing Boost dependencies
+  - echo "Testing $BOOST/libs/$BOOST_LIBS_FOLDER moved from $TRAVIS_BUILD_DIR, branch $BOOST_BRANCH"
+  - rm -rf $BOOST/libs/$BOOST_LIBS_FOLDER || true
+  - mv $TRAVIS_BUILD_DIR $BOOST/libs/$BOOST_LIBS_FOLDER
+  - python tools/boostdep/depinst/depinst.py --git_args "--depth 1 --jobs 2" $BOOST_LIBS_FOLDER
+  - git status
+
+  # Adding missing toolsets and preparing Boost headers
+  - ./bootstrap.sh
+  - ./b2 headers
+  - |-
+    echo "using gcc ;" >> ~/user-config.jam
+    echo "using clang ;" >> ~/user-config.jam
+    echo "using clang : 3.8 : clang++-3.8 ;" >> ~/user-config.jam
+    echo "using clang : 4 : clang++-4.0 ;" >> ~/user-config.jam
+    echo "using clang : 5 : clang++-5.0 ;" >> ~/user-config.jam
+    echo "using clang : 6 : clang++-6.0 ;" >> ~/user-config.jam
+    echo "using clang : 7 : clang++-7 ;" >> ~/user-config.jam
+    echo "using clang : 8 : clang++-8 ;" >> ~/user-config.jam
+    echo "using clang : libc++ : clang++-libc++ ;" >> ~/user-config.jam
+  - cd $BOOST/libs/$BOOST_LIBS_FOLDER/test/
 
 script:
-    # `--coverage` flags required to generate coverage info for Coveralls
-    - ../../../b2 "testing.launcher=LD_PRELOAD=/usr/lib/x86_64-linux-gnu/libasan.so.3 " address-model=64 architecture=x86 toolset=$TOOLSET cxxflags="--coverage -fsanitize=address,leak,undefined -DBOOST_TRAVISCI_BUILD $CXX_FLAGS" linkflags="$LINK_FLAGS --coverage -lasan -lubsan"
+  - sh -c "../../../b2 -j2 $B2_ARGS"
 
 after_success:
-    # Copying Coveralls data to a separate folder
-    - mkdir -p $TRAVIS_BUILD_DIR/coverals
-    - find ../../../bin.v2/ -name "*.gcda" -exec cp "{}" $TRAVIS_BUILD_DIR/coverals/ \;
-    - find ../../../bin.v2/ -name "*.gcno" -exec cp "{}" $TRAVIS_BUILD_DIR/coverals/ \;
-    - find ../../../bin.v2/ -name "*.da" -exec cp "{}" $TRAVIS_BUILD_DIR/coverals/ \;
-    - find ../../../bin.v2/ -name "*.no" -exec cp "{}" $TRAVIS_BUILD_DIR/coverals/ \;
-    - wget https://github.com/linux-test-project/lcov/archive/v1.12.zip
-    - unzip v1.12.zip
-    - LCOV="`pwd`/lcov-1.12/bin/lcov --gcov-tool gcov-6"
+  # Copying Coveralls data to a separate folder
+  - mkdir -p $TRAVIS_BUILD_DIR/coverals
+  - find ../../../bin.v2/ -name "*.gcda" -exec cp "{}" $TRAVIS_BUILD_DIR/coverals/ \;
+  - find ../../../bin.v2/ -name "*.gcno" -exec cp "{}" $TRAVIS_BUILD_DIR/coverals/ \;
+  - find ../../../bin.v2/ -name "*.da" -exec cp "{}" $TRAVIS_BUILD_DIR/coverals/ \;
+  - find ../../../bin.v2/ -name "*.no" -exec cp "{}" $TRAVIS_BUILD_DIR/coverals/ \;
+  - wget https://github.com/linux-test-project/lcov/archive/v1.12.zip
+  - unzip v1.12.zip
+  - LCOV="`pwd`/lcov-1.12/bin/lcov --gcov-tool gcov-6"
 
-    # Preparing Coveralls data by changind data format to a readable one
-    - echo "$LCOV --directory $TRAVIS_BUILD_DIR/coverals --base-directory `pwd` --capture --output-file $TRAVIS_BUILD_DIR/coverals/coverage.info"
-    - $LCOV --directory $TRAVIS_BUILD_DIR/coverals --base-directory `pwd` --capture --output-file $TRAVIS_BUILD_DIR/coverals/coverage.info
+  # Preparing Coveralls data by changind data format to a readable one
+  - echo "$LCOV --directory $TRAVIS_BUILD_DIR/coverals --base-directory `pwd` --capture --output-file $TRAVIS_BUILD_DIR/coverals/coverage.info"
+  - $LCOV --directory $TRAVIS_BUILD_DIR/coverals --base-directory `pwd` --capture --output-file $TRAVIS_BUILD_DIR/coverals/coverage.info
 
-    # ... erasing /test/ /example/ folder data
-    - cd $BOOST
-    - $LCOV --remove $TRAVIS_BUILD_DIR/coverals/coverage.info "/usr*" "*/$PROJECT_TO_TEST/test/*" $IGNORE_COVERAGE "*/$PROJECT_TO_TEST/tests/*" "*/$PROJECT_TO_TEST/examples/*" "*/$PROJECT_TO_TEST/example/*" -o $TRAVIS_BUILD_DIR/coverals/coverage.info
+  # ... erasing /test/ /example/ folder data
+  - cd $BOOST
+  - $LCOV --remove $TRAVIS_BUILD_DIR/coverals/coverage.info "/usr*" "*/$BOOST_LIBS_FOLDER/test/*" $IGNORE_COVERAGE "*/$BOOST_LIBS_FOLDER/tests/*" "*/$BOOST_LIBS_FOLDER/examples/*" "*/$BOOST_LIBS_FOLDER/example/*" -o $TRAVIS_BUILD_DIR/coverals/coverage.info
 
-    # ... erasing data that is not related to this project directly
-    - OTHER_LIBS=`grep "submodule .*" .gitmodules | sed 's/\[submodule\ "\(.*\)"\]/"\*\/boost\/\1\.hpp" "\*\/boost\/\1\/\*"/g'| sed "/\"\*\/boost\/$PROJECT_TO_TEST\/\*\"/d" | sed ':a;N;$!ba;s/\n/ /g'`
-    - echo $OTHER_LIBS
-    - eval "$LCOV --remove $TRAVIS_BUILD_DIR/coverals/coverage.info $OTHER_LIBS -o $TRAVIS_BUILD_DIR/coverals/coverage.info"
+  # ... erasing data that is not related to this project directly
+  - OTHER_LIBS=`grep "submodule .*" .gitmodules | sed 's/\[submodule\ "\(.*\)"\]/"\*\/boost\/\1\.hpp" "\*\/boost\/\1\/\*"/g'| sed "/\"\*\/boost\/$BOOST_LIBS_FOLDER\/\*\"/d" | sed ':a;N;$!ba;s/\n/ /g'`
+  - echo $OTHER_LIBS
+  - eval "$LCOV --remove $TRAVIS_BUILD_DIR/coverals/coverage.info $OTHER_LIBS -o $TRAVIS_BUILD_DIR/coverals/coverage.info"
 
-    # Sending data to Coveralls
-    - cd $TRAVIS_BUILD_DIR
-    - gem install coveralls-lcov
-    - coveralls-lcov coverals/coverage.info
+  # Sending data to Coveralls
+  - cd $TRAVIS_BUILD_DIR
+  - gem install coveralls-lcov
+  - coveralls-lcov coverals/coverage.info

CMakeLists.txt

@@ -0,0 +1,24 @@
+# Copyright 2019 Mike Dev
+# Distributed under the Boost Software License, Version 1.0.
+# See accompanying file LICENSE_1_0.txt or copy at https://www.boost.org/LICENSE_1_0.txt
+#
+# NOTE: CMake support for Boost.Conversion is currently experimental at best
+#       and the interface is likely to change in the future
+
+cmake_minimum_required( VERSION 3.5 )
+project( BoostConversion LANGUAGES CXX )
+
+add_library( boost_conversion INTERFACE )
+add_library( Boost::conversion ALIAS boost_conversion )
+
+target_include_directories( boost_conversion INTERFACE include )
+
+target_link_libraries( boost_conversion
+    INTERFACE
+        Boost::assert
+        Boost::config
+        Boost::smart_ptr
+        Boost::throw_exception
+        Boost::type_traits
+        Boost::typeof
+)

doc/conversion.qbk

@@ -1,5 +1,7 @@
 [/
     Copyright 2016 Mikhail Maximov.
+    Copyright 2020 Antony Polukhin.
+
     Distributed under the Boost Software License, Version 1.0. (See accompanying
     file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt">http://www.boost.org/LICENSE_1_0.txt</a>)
 ]
@@ -8,15 +10,15 @@
     [quickbook 1.6]
     [compatibility-mode 1.5]
     [id conversion]
-    [version 1.6]
+    [version 1.7]
     [authors [Stroustrup, Bjarne], [Abrahams, Dave], [Rasin, Boris], [Polukhin, Antony]]
-    [copyright 2001 Beman Dawes]
+    [copyright 2001 Beman Dawes, 2014-2020 Antony Polukhin]
     [license
         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])
     ]
-    [source-mode teletype]
+    [source-mode c++]
 ]
 
 [/ QuickBook Document version 1.5 ]
@@ -44,7 +46,7 @@ the Boost Conversion Library is supplied by several headers:
   provides [@boost:libs/lexical_cast/doc/html/index.html `lexical_cast<>`] general literal text conversions, such as an `int` represented as a `string`, or vice-versa. 
 
 [endsect]
-  
+
 [section Polymorphic casts]
 Pointers to polymorphic objects (objects of classes which define at
 least one virtual function) are sometimes downcast or crosscast.
@@ -58,6 +60,7 @@ safety, suffer poor readability, and are difficult to locate with search
 tools.
 
 [#polymorphic_downcast]
+[section polymorphic_downcast]
 
 The C++ built-in `static_cast` can be used for efficiently
 downcasting pointers to polymorphic objects, but provides no error
@@ -68,11 +71,11 @@ debug compilations adds safety via an `assert()` that a `dynamic_cast`
 succeeds.
 
 A `polymorphic_downcast` should be used for
-downcasts that you are certain should succeed.  Error checking is
+downcasts that you are certain should succeed. Error checking is
 only performed in translation units where `NDEBUG` is
 not defined, via
 ```
-	assert( dynamic_cast<Derived>(x) == x )
+    assert( dynamic_cast<Derived>(x) == x )
 ```
 where `x` is the source pointer.  This approach
 ensures that not only is a non-zero pointer returned, but also
@@ -81,17 +84,33 @@ Attempts to crosscast using `polymorphic_downcast` will
 fail to compile.
 
 [warning Because `polymorphic_downcast` uses `assert()`, it
-violates the One Definition Rule (ODR) if NDEBUG is inconsistently
+violates the One Definition Rule (ODR) if `NDEBUG` is inconsistently
 defined across translation units. See ISO Std 3.2]
 
+[h4 Example:]
+```
+    #include <boost/polymorphic_cast.hpp>
+    ...
+    class Fruit { public: virtual ~Fruit(){}; ... };
+    class Banana : public Fruit { ... };
+    ...
+    void f( Fruit * fruit ) {
+      // ... logic which leads us to believe it is a Banana
+      Banana * banana = boost::polymorphic_downcast<Banana*>(fruit);
+      ...
+    }
+```
+[endsect]
+
 [#polymorphic_cast]
+[section polymorphic_cast]
 
 The C++ built-in `dynamic_cast` can be used for downcasts and
 crosscasts of pointers to polymorphic objects, but error notification in
 the form of a returned value of 0 is inconvenient to test, or worse yet,
 easy to forget to test. The throwing form of `dynamic_cast`, which
 works on references, can be used on pointers through the ugly expression
-`&dynamic_cast<T&>(*p), which causes undefined 
+`&dynamic_cast<T&>(*p)`, which causes undefined
 behavior if `p` is `0`. The `polymorphic_cast`
 template performs a `dynamic_cast` on a pointer, and throws an
 exception if the `dynamic_cast` returns 0.
@@ -99,91 +118,91 @@ exception if the `dynamic_cast` returns 0.
 For crosscasts, or when the success of a cast can only be known at runtime, 
 or when efficiency is not important, `polymorphic_cast` is preferred.
 
-The C++ built-in dynamic_cast must be used to cast references rather than pointers.
+The C++ built-in `dynamic_cast` must be used to cast references rather than pointers.
 It is also the only cast that can be used to check whether a given interface is supported; in that case a return of 0 isn't an error condition.
 
+[endsect]
+
+
 [#polymorphic_pointer_cast]
-While polymorphic_downcast and polymorphic_cast work with built-in pointer types only,
-polymorphic_pointer_downcast and polymorphic_pointer_cast are more generic versions
+[section polymorphic_pointer_cast]
+While `polymorphic_downcast` and `polymorphic_cast` work with built-in pointer types only,
+`polymorphic_pointer_downcast` and `polymorphic_pointer_cast` are more generic versions
 with support for any pointer type for which the following expressions would be valid:
 
 For `polymorphic_pointer_downcast`:
 ```
-	static_pointer_cast<Derived>(p);
-	dynamic_pointer_cast<Derived>(p);
+    static_pointer_cast<Derived>(p);
+    dynamic_pointer_cast<Derived>(p);
 ```
 For `polymorphic_pointer_cast`:
 ```
-	dynamic_pointer_cast<Derived>(p);
-	!p; // conversion to bool with negation
+    dynamic_pointer_cast<Derived>(p);
+    !p; // conversion to bool with negation
 ```
 
 This includes C++ built-in pointers, `std::shared_ptr`,
 `boost::shared_ptr`, `boost::intrusive_ptr`, etc.
 
-[endsect]
-[section `polymorphic_cast`, `polymorphic_downcast`, `polymorphic_pointer_cast` and `polymorphic_pointer_downcast` synopsis]
+
+[h4 Example:]
 ```
-	namespace boost {
+    #include <boost/polymorphic_pointer_cast.hpp>
 
-	template <class Derived, class Base>
-	inline Derived polymorphic_cast(Base* x);
-	// Throws: std::bad_cast if ( dynamic_cast<Derived>(x) == 0 )
-	// Returns: dynamic_cast<Derived>(x)
+    class Fruit { public: virtual ~Fruit(){} };
+    class Banana : public Fruit {};
 
-	template <class Derived, class Base>
-	inline Derived polymorphic_downcast(Base* x);
-	// Effects: assert( dynamic_cast<Derived>(x) == x );
-	// Returns: static_cast<Derived>(x)
+    // Use one of these:
+    typedef Fruit* FruitPtr;
+    typedef std::shared_ptr<Fruit> FruitPtr;
+    typedef boost::shared_ptr<Fruit> FruitPtr;
+    typedef boost::intrusive_ptr<Fruit> FruitPtr;
 
-	template <class Derived, class Base>
-	inline auto polymorphic_pointer_cast(Base x);
-	// Throws: std::bad_cast if ( dynamic_pointer_cast<Derived>(x) == 0 )
-	// Returns: dynamic_pointer_cast<Derived>(x)
+    void f(FruitPtr fruit) {
+      // ... logic which leads us to believe it is a banana
+      auto banana = boost::polymorphic_pointer_downcast<Banana>(fruit);
+      ...
+    }
+```
 
-	template <class Derived, class Base>
-	inline auto polymorphic_pointer_downcast(Base x);
-	// Effects: assert( dynamic_pointer_cast<Derived>(x) == x );
-	// Returns: static_pointer_cast<Derived>(x)
+[endsect]
 
-	}
+[endsect]
+
+[section Synopsis]
+```
+    namespace boost {
+
+    // Throws: std::bad_cast if ( dynamic_cast<Derived>(x) == 0 )
+    // Returns: dynamic_cast<Derived>(x)
+    template <class Derived, class Base>
+    inline Derived polymorphic_cast(Base* x);
+
+    // Effects: assert( dynamic_cast<Derived>(x) == x );
+    // Returns: static_cast<Derived>(x)
+    template <class Derived, class Base>
+    inline Derived polymorphic_downcast(Base* x);
+
+    // Effects: assert( dynamic_cast<Derived>(&x) == &x );
+    // Returns: static_cast<Derived>(x)
+    template <class Derived, class Base>
+    inline Derived polymorphic_downcast(Base& x);
+
+    // Throws: std::bad_cast if ( dynamic_pointer_cast<Derived>(x) == 0 )
+    // Returns: dynamic_pointer_cast<Derived>(x)
+    template <class Derived, class Base>
+    inline auto polymorphic_pointer_cast(Base x);
+
+    // Effects: assert( dynamic_pointer_cast<Derived>(x) == x );
+    // Returns: static_pointer_cast<Derived>(x)
+    template <class Derived, class Base>
+    inline auto polymorphic_pointer_downcast(Base x);
+
+    }
 ```
 [endsect]
-[section `polymorphic_downcast` example]
-```
-	#include <boost/polymorphic_cast.hpp>
-	...
-	class Fruit { public: virtual ~Fruit(){}; ... };
-	class Banana : public Fruit { ... };
-	...
-	void f( Fruit * fruit ) {
-	  // ... logic which leads us to believe it is a Banana
-	  Banana * banana = boost::polymorphic_downcast<Banana*>(fruit);
-	  ...
-	}
-```
-[endsect]
-[section `polymorphic_pointer_downcast` example]
-```
-	#include <boost/polymorphic_pointer_cast.hpp>
 
-	class Fruit { public: virtual ~Fruit(){} };
-	class Banana : public Fruit {};
 
-	// use one of these:
-
-	typedef Fruit* FruitPtr;
-	typedef std::shared_ptr<Fruit> FruitPtr;
-	typedef boost::shared_ptr<Fruit> FruitPtr;
-	typedef boost::intrusive_ptr<Fruit> FruitPtr;
-
-	void f(FruitPtr fruit) {
-	  // ... logic which leads us to believe it is a banana
-	  auto banana = boost::polymorphic_pointer_downcast<Banana>(fruit);
-	  ...
-	}
-```
-[endsect]
 [section History]
 `polymorphic_cast` was suggested by Bjarne Stroustrup in "The C++ Programming Language".
 
@@ -192,6 +211,8 @@ This includes C++ built-in pointers, `std::shared_ptr`,
 `polymorphic_pointer_downcast` was contributed by [@http://www.boost.org/people/boris_rasin.htm Boris Rasin]
 and `polymorphic_pointer_cast` by Antony Polukhin.
 
-An old numeric_cast that was contributed by [@http://www.boost.org/people/kevlin_henney.htm Kevlin Henney]
-is now superseeded by the [@boost:numeric_conversion/doc/html/html/boost_numericconversion/improved_numeric_cast__.html Boost Numeric Conversion Library]
+`polymorphic_downcast` overload for references was contributed by Julien Delacroix.
+
+An old `numeric_cast` that was contributed by [@http://www.boost.org/people/kevlin_henney.htm Kevlin Henney]
+is now superseded by the [@boost:numeric_conversion/doc/html/html/boost_numericconversion/improved_numeric_cast__.html Boost Numeric Conversion Library]
 [endsect]

include/boost/implicit_cast.hpp

@@ -2,8 +2,9 @@
 // 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)
-#ifndef IMPLICIT_CAST_DWA200356_HPP
-# define IMPLICIT_CAST_DWA200356_HPP
+
+#ifndef BOOST_IMPLICIT_CAST_DWA200356_HPP
+#define BOOST_IMPLICIT_CAST_DWA200356_HPP
 
 namespace boost {
 
@@ -26,11 +27,7 @@ inline T implicit_cast (typename boost::detail::icast_identity<T>::type x) {
     return x;
 }
 
-// incomplete return type now is here
-//template <typename T>
-//void implicit_cast (...);
-
 } // namespace boost
 
 
-#endif // IMPLICIT_CAST_DWA200356_HPP
+#endif // BOOST_IMPLICIT_CAST_DWA200356_HPP

include/boost/polymorphic_cast.hpp

@@ -50,14 +50,20 @@
 #define BOOST_POLYMORPHIC_CAST_HPP
 
 # include <boost/config.hpp>
-# include <boost/assert.hpp>
-# include <boost/throw_exception.hpp>
-# include <typeinfo>
 
 #ifdef BOOST_HAS_PRAGMA_ONCE
 #   pragma once
 #endif
 
+# include <boost/assert.hpp>
+# include <boost/core/addressof.hpp>
+# include <boost/core/enable_if.hpp>
+# include <boost/throw_exception.hpp>
+# include <boost/type_traits/is_reference.hpp> 
+# include <boost/type_traits/remove_reference.hpp>
+
+# include <typeinfo>
+
 namespace boost
 {
 //  See the documentation for descriptions of how to choose between
@@ -79,7 +85,7 @@ namespace boost
 
 //  polymorphic_downcast  ----------------------------------------------------//
 
-    //  BOOST_ASSERT() checked polymorphic downcast.  Crosscasts prohibited.
+    //  BOOST_ASSERT() checked raw pointer polymorphic downcast.  Crosscasts prohibited.
 
     //  WARNING: Because this cast uses BOOST_ASSERT(), it violates
     //  the One Definition Rule if used in multiple translation units
@@ -95,6 +101,26 @@ namespace boost
         return static_cast<Target>(x);
     }
 
+    //  BOOST_ASSERT() checked reference polymorphic downcast.  Crosscasts prohibited.
+
+    //  WARNING: Because this cast uses BOOST_ASSERT(), it violates
+    //  the One Definition Rule if used in multiple translation units
+    //  where BOOST_DISABLE_ASSERTS, BOOST_ENABLE_ASSERT_HANDLER
+    //  NDEBUG are defined inconsistently.
+
+    //  Contributed by Julien Delacroix
+
+    template <class Target, class Source>
+    inline typename boost::enable_if_c<
+        boost::is_reference<Target>::value, Target
+    >::type polymorphic_downcast(Source& x)
+    {
+        typedef typename boost::remove_reference<Target>::type* target_pointer_type;
+        return *boost::polymorphic_downcast<target_pointer_type>(
+            boost::addressof(x)
+        );
+    }
+
 } // namespace boost
 
 #endif  // BOOST_POLYMORPHIC_CAST_HPP

include/boost/polymorphic_pointer_cast.hpp

@@ -1,5 +1,5 @@
 //  boost polymorphic_pointer_cast.hpp header file  ----------------------------------------------//
-//  (C) Copyright Boris Rasin and Antony Polukhin 2014-2015.
+//  (C) Copyright Boris Rasin and Antony Polukhin 2014-2019.
 //  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)

test/appveyor.yml

@@ -2,23 +2,26 @@
 # subject to 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)
 #
-# Copyright Antony Polukhin 2016-2017.
+# Copyright Antony Polukhin 2016-2019.
 
 #
 # See https://svn.boost.org/trac/boost/wiki/TravisCoverals for description of this file
 # and how it can be used with Boost libraries.
 #
-# File revision #5
+# File revision #6
 
 init:
-    - set BRANCH_TO_TEST=%APPVEYOR_REPO_BRANCH%  # Change to branch you wish to test. Use %APPVEYOR_REPO_BRANCH% for current branch.
-    - set BOOST_REMOVE=conversion                # Remove this folder from lib from full clone of Boost. If you are testing `any` repo, write here `any`.
+    # boost-local/libs/ folder to put this library into. This may be useful, if you're for example running Travis
+    # from `Boost.DLL` repo while Boost already has `dll` and with to replace `dll` with content of`Boost.DLL`.
+    #
+    # Otherwise just leave the default value - set BOOST_LIBS_FOLDER=%APPVEYOR_PROJECT_NAME%
+    - set BOOST_LIBS_FOLDER=%APPVEYOR_PROJECT_NAME%
 
 ###############################################################################################################
 # From this point and below code is same for all the Boost libs
 ###############################################################################################################
 
-version: 1.64.{build}-{branch}
+version: 1.71.{build}-{branch}
  
 # branches to build
 branches:
@@ -27,32 +30,58 @@ branches:
 
 skip_tags: true
 
+environment:
+  matrix:
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
+      TOOLSET: msvc-9.0,msvc-10.0,msvc-11.0,msvc-12.0
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
+      TOOLSET: msvc-14.1,clang-win
+      CXXSTD: 14,17
+      ADDRMD: 32,64
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
+      ADDPATH: C:\cygwin\bin;
+      TOOLSET: gcc
+      CXXSTD: 03,11,14,1z
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
+      ADDPATH: C:\cygwin64\bin;
+      TOOLSET: gcc
+      CXXSTD: 03,11,14,1z
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
+      ADDPATH: C:\mingw\bin;
+      TOOLSET: gcc
+      CXXSTD: 03,11,14,1z
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
+      ADDPATH: C:\mingw-w64\x86_64-7.2.0-posix-seh-rt_v5-rev1\mingw64\bin;
+      TOOLSET: gcc
+      CXXSTD: 03,11,14,1z
+
 before_build:
-    - set PATH=%PATH%;C:\\MinGW\\bin
+    - set BOOST_BRANCH=develop
+    - if "%APPVEYOR_REPO_BRANCH%" == "master" set BOOST_BRANCH=master
     - echo "Testing %APPVEYOR_PROJECT_NAME%"
     # Cloning Boost libraries (fast nondeep cloning)
     - set BOOST=C:/boost-local
-    - git init %BOOST%
+    - git clone -b %BOOST_BRANCH% --depth 10 https://github.com/boostorg/boost.git %BOOST%
     - cd %BOOST%
-    - git remote add --no-tags -t %BRANCH_TO_TEST% origin https://github.com/boostorg/boost.git
-    - git fetch --depth=1
-    - git checkout %BRANCH_TO_TEST%
-    - git submodule update --init --merge --jobs 16
-    - git remote set-branches --add origin %BRANCH_TO_TEST%
-    #- git pull --recurse-submodules        # Updaes submodules to most recent version. Not required
-    - rm -rf %BOOST%/libs/%BOOST_REMOVE%
-    - mv %APPVEYOR_BUILD_FOLDER% %BOOST%/libs/%APPVEYOR_PROJECT_NAME%
+    - git submodule update --init --depth 10 tools/build tools/boostdep
+
+    - rm -rf %BOOST%/libs/%BOOST_LIBS_FOLDER%
+    - mv -f %APPVEYOR_BUILD_FOLDER% %BOOST%/libs/%BOOST_LIBS_FOLDER%
+    - python tools/boostdep/depinst/depinst.py --git_args "--depth 1 --jobs 2" %BOOST_LIBS_FOLDER%
 
 build_script:
-    - call "C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\vcvarsall.bat" x64
-    - bootstrap.bat
+    - cmd /c bootstrap
     - b2.exe headers
-    - cd %BOOST%/libs/%APPVEYOR_PROJECT_NAME%/test
+    - cd %BOOST%/libs/%BOOST_LIBS_FOLDER%/test
 
 after_build:
 before_test:
 test_script:
-    - ..\..\..\b2.exe address-model=32 architecture=x86 toolset=msvc,gcc cxxflags="-DBOOST_TRAVISCI_BUILD" -sBOOST_BUILD_PATH=.
+  - PATH=%ADDPATH%%PATH%
+  - if not "%CXXSTD%" == "" set CXXSTD=cxxstd=%CXXSTD%
+  - if not "%ADDRMD%" == "" set ADDRMD=address-model=%ADDRMD%
+  - echo "Running command ..\..\..\b2 -j3 toolset=%TOOLSET% %CXXSTD% %ADDRMD% variant=debug,release"
+  - ..\..\..\b2.exe -j3 toolset=%TOOLSET% %CXXSTD% %ADDRMD% variant=debug,release cxxflags="-DBOOST_TRAVISCI_BUILD"
 
 after_test:
 on_success:

test/cast_test.cpp

@@ -72,7 +72,7 @@ int main( int argc, char * argv[] )
 
     bool caught_exception = false;
     try { derived = polymorphic_cast<Derived*>( base ); }
-    catch (std::bad_cast)
+    catch (const std::bad_cast&)
         { cout<<"caught bad_cast\n"; caught_exception = true; }
     BOOST_TEST( caught_exception );
     //  the following is just so generated code can be inspected

test/polymorphic_cast_test.cpp

@@ -172,20 +172,23 @@ static void test_polymorphic_pointer_cast()
 
 static void test_polymorphic_downcast()
 {
-    Base * base = new Derived;
+    Base *base_pointer = new Derived;
 
-    Derived * derived = boost::polymorphic_downcast<Derived*>( base );
+    // test raw pointer cast
+    Derived *derived_pointer = boost::polymorphic_downcast<Derived *>(base_pointer);
 
-    BOOST_TEST( derived != 0 );
+    BOOST_TEST(derived_pointer != 0);
 
-    if( derived != 0 )
+    if (derived_pointer != 0)
     {
-        BOOST_TEST_EQ( derived->kind(), "Derived" );
+        BOOST_TEST_EQ(derived_pointer->kind(), "Derived");
     }
 
-    // polymorphic_downcast can't do crosscasts
+    // test reference cast
+    Derived& derived_ref = boost::polymorphic_downcast<Derived&>(*base_pointer);
+    BOOST_TEST_EQ(derived_ref.kind(), "Derived");
 
-    delete base;
+    delete base_pointer;
 }
 
 static void test_polymorphic_pointer_downcast_builtin()
@@ -278,17 +281,32 @@ static void test_polymorphic_pointer_cast_fail()
 
 static void test_polymorphic_downcast_fail()
 {
-    Base * base = new Base;
+    Base * base_pointer = new Base;
 
-    int old_count = assertion_failed_count;
-    expect_assertion = true;
+    {
+        // test raw pointer cast
 
-    BOOST_TEST_THROWS( boost::polymorphic_downcast<Derived*>( base ), expected_assertion ); // should assert
+        int old_count = assertion_failed_count;
+        expect_assertion = true;
 
-    BOOST_TEST_EQ( assertion_failed_count, old_count + 1 );
-    expect_assertion = false;
+        BOOST_TEST_THROWS(boost::polymorphic_downcast<Derived *>(base_pointer), expected_assertion); // should assert
 
-    delete base;
+        BOOST_TEST_EQ(assertion_failed_count, old_count + 1);
+        expect_assertion = false;
+    }
+    {
+        // test reference cast
+
+        int old_count = assertion_failed_count;
+        expect_assertion = true;
+
+        BOOST_TEST_THROWS(boost::polymorphic_downcast<Derived &>(*base_pointer), expected_assertion); // should assert
+
+        BOOST_TEST_EQ(assertion_failed_count, old_count + 1);
+        expect_assertion = false;
+    }
+
+    delete base_pointer;
 }
 
 static void test_polymorphic_pointer_downcast_builtin_fail()