From bdd449ae6a5ab8291763e8a84a2b3404c0fcaba0 Mon Sep 17 00:00:00 2001
From: Peter Dimov <pdimov@pdimov.com>
Date: Fri, 2 Jun 2017 22:11:29 +0300
Subject: [PATCH] get_if should return 0 when passed 0

---
 include/boost/variant2/variant.hpp | 12 +++----
 test/variant_get_by_index.cpp      | 50 ++++++++++++++++++++++++++++++
 test/variant_get_by_type.cpp       | 44 ++++++++++++++++++++++++++
 3 files changed, 100 insertions(+), 6 deletions(-)

diff --git a/include/boost/variant2/variant.hpp b/include/boost/variant2/variant.hpp
index cb669ad..7e78a6a 100644
--- a/include/boost/variant2/variant.hpp
+++ b/include/boost/variant2/variant.hpp
@@ -112,7 +112,7 @@ template<class U, class... T> constexpr bool holds_alternative( variant<T...> co
     return v.index() == mp_find<variant<T...>, U>::value;
 }
 
-// get
+// get (index)
 
 template<std::size_t I, class... T> constexpr variant_alternative_t<I, variant<T...>>& get(variant<T...>& v)
 {
@@ -178,7 +178,7 @@ template<std::size_t I, class... T> constexpr variant_alternative_t<I, variant<T
 #endif
 }
 
-// get
+// get (type)
 
 template<class U, class... T> constexpr U& get(variant<T...>& v)
 {
@@ -253,13 +253,13 @@ template<class U, class... T> constexpr U const&& get(variant<T...> const&& v)
 template<std::size_t I, class... T> constexpr std::add_pointer_t<variant_alternative_t<I, variant<T...>>> get_if(variant<T...>* v) noexcept
 {
     static_assert( I < sizeof...(T), "Index out of bounds" );
-    return v->index() == I? &v->_get_impl( mp_size_t<I>() ): 0;
+    return v && v->index() == I? &v->_get_impl( mp_size_t<I>() ): 0;
 }
 
 template<std::size_t I, class... T> constexpr std::add_pointer_t<const variant_alternative_t<I, variant<T...>>> get_if(variant<T...> const * v) noexcept
 {
     static_assert( I < sizeof...(T), "Index out of bounds" );
-    return v->index() == I? &v->_get_impl( mp_size_t<I>() ): 0;
+    return v && v->index() == I? &v->_get_impl( mp_size_t<I>() ): 0;
 }
 
 template<class U, class... T> constexpr std::add_pointer_t<U> get_if(variant<T...>* v) noexcept
@@ -267,7 +267,7 @@ template<class U, class... T> constexpr std::add_pointer_t<U> get_if(variant<T..
     static_assert( mp_count<variant<T...>, U>::value == 1, "The type must occur exactly once in the list of variant alternatives" );
     constexpr auto I = mp_find<variant<T...>, U>::value;
 
-    return v->index() == I? &v->_get_impl( mp_size_t<I>() ): 0;
+    return v && v->index() == I? &v->_get_impl( mp_size_t<I>() ): 0;
 }
 
 template<class U, class... T> constexpr std::add_pointer_t<U const> get_if(variant<T...> const * v) noexcept
@@ -275,7 +275,7 @@ template<class U, class... T> constexpr std::add_pointer_t<U const> get_if(varia
     static_assert( mp_count<variant<T...>, U>::value == 1, "The type must occur exactly once in the list of variant alternatives" );
     constexpr auto I = mp_find<variant<T...>, U>::value;
 
-    return v->index() == I? &v->_get_impl( mp_size_t<I>() ): 0;
+    return v && v->index() == I? &v->_get_impl( mp_size_t<I>() ): 0;
 }
 
 //
diff --git a/test/variant_get_by_index.cpp b/test/variant_get_by_index.cpp
index b55313e..950e73a 100644
--- a/test/variant_get_by_index.cpp
+++ b/test/variant_get_by_index.cpp
@@ -196,5 +196,55 @@ int main()
         BOOST_TEST_EQ( get<2>(std::move(v)), 3.14f );
     }
 
+    {
+        variant<int> * p = 0;
+        BOOST_TEST_EQ( get_if<0>(p), nullptr );
+    }
+
+    {
+        variant<int const> * p = 0;
+        BOOST_TEST_EQ( get_if<0>(p), nullptr );
+    }
+
+    {
+        variant<int> const * p = 0;
+        BOOST_TEST_EQ( get_if<0>(p), nullptr );
+    }
+
+    {
+        variant<int const> const * p = 0;
+        BOOST_TEST_EQ( get_if<0>(p), nullptr );
+    }
+
+    {
+        variant<int, float> * p = 0;
+        BOOST_TEST_EQ( get_if<0>(p), nullptr );
+    }
+
+    {
+        variant<int, float> const * p = 0;
+        BOOST_TEST_EQ( get_if<0>(p), nullptr );
+    }
+
+    {
+        variant<int const, float volatile> * p = 0;
+        BOOST_TEST_EQ( get_if<0>(p), nullptr );
+    }
+
+    {
+        variant<int const, float volatile> const * p = 0;
+        BOOST_TEST_EQ( get_if<0>(p), nullptr );
+    }
+
+    {
+        variant<int, int, float, float> * p = 0;
+        BOOST_TEST_EQ( get_if<0>(p), nullptr );
+    }
+
+    {
+        variant<int, int, float, float> const * p = 0;
+        BOOST_TEST_EQ( get_if<0>(p), nullptr );
+    }
+
     return boost::report_errors();
 }
diff --git a/test/variant_get_by_type.cpp b/test/variant_get_by_type.cpp
index 82b18c7..5a179dc 100644
--- a/test/variant_get_by_type.cpp
+++ b/test/variant_get_by_type.cpp
@@ -162,5 +162,49 @@ int main()
         BOOST_TEST_EQ( get_if<float>(&v), &get<float>(v) );
     }
 
+    {
+        variant<int> * p = 0;
+        BOOST_TEST_EQ( get_if<int>(p), nullptr );
+    }
+
+    {
+        variant<int const> * p = 0;
+        BOOST_TEST_EQ( get_if<int const>(p), nullptr );
+    }
+
+    {
+        variant<int> const * p = 0;
+        BOOST_TEST_EQ( get_if<int>(p), nullptr );
+    }
+
+    {
+        variant<int const> const * p = 0;
+        BOOST_TEST_EQ( get_if<int const>(p), nullptr );
+    }
+
+    {
+        variant<int, float> * p = 0;
+
+        BOOST_TEST_EQ( get_if<int>(p), nullptr );
+        BOOST_TEST_EQ( get_if<float>(p), nullptr );
+    }
+
+    {
+        variant<int, float> const * p = 0;
+
+        BOOST_TEST_EQ( get_if<int>(p), nullptr );
+        BOOST_TEST_EQ( get_if<float>(p), nullptr );
+    }
+
+    {
+        variant<int, int, float> * p = 0;
+        BOOST_TEST_EQ( get_if<float>(p), nullptr );
+    }
+
+    {
+        variant<int, int, float> const * p = 0;
+        BOOST_TEST_EQ( get_if<float>(p), nullptr );
+    }
+
     return boost::report_errors();
 }