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boost::polymorphic_downcast only supports raw pointer cast, which is a gap compared to static_cast.

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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.
This commit is contained in:
Julien DELACROIX
2019-12-09 08:51:10 +01:00
parent 9d4a518e74
commit e130cd860c
2 changed files with 52 additions and 15 deletions
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test/polymorphic_cast_test.cpp
+32 -14
View File
@@ -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()