Compile Errors When Including Boost 1.79.0 Bimap w/ Unreal 5

Question

For over a year, I was using Boost's Bimap for the basis of an inventory system.

typedef boost::bimap<boost::bimaps::set_of<uint32>,
    boost::bimaps::multiset_of<uint32>,
    boost::bimaps::with_info<FItemDetails>> InventoryBimap;

After updating from Unreal 4 to Unreal 5, though, I made a few other changes. I moved from Boost 1.68.0 to 1.79.0. I moved from C++17 to C++20.

Edit: Sorry, I forgot to include I'm using Visual Studio 2022.

There are two sources for a bunch of compilation errors that prevent my game from compiling:

1>H:\UnrealEngine\Engine\Source\ThirdParty\boost\boost-1_79_0\include\boost\core\pointer_traits.hpp(120): error C2988: unrecognizable template declaration/definition
1>H:\UnrealEngine\Engine\Source\ThirdParty\boost\boost-1_79_0\include\boost\core\pointer_traits.hpp(127): note: see reference to class template instantiation 'boost::detail::ptr_to_expr<T,E>' being compiled
1>H:\UnrealEngine\Engine\Source\ThirdParty\boost\boost-1_79_0\include\boost\core\pointer_traits.hpp(120): error C2059: syntax error: '<end Parse>'
1>H:\UnrealEngine\Engine\Source\ThirdParty\boost\boost-1_79_0\include\boost\core\pointer_traits.hpp(120): error C2334: unexpected token(s) preceding '{'; skipping apparent function body
1>H:\UnrealEngine\Engine\Source\ThirdParty\boost\boost-1_79_0\include\boost\core\pointer_traits.hpp(120): error C2988: unrecognizable template declaration/definition
1>H:\UnrealEngine\Engine\Source\ThirdParty\boost\boost-1_79_0\include\boost\core\pointer_traits.hpp(120): error C2059: syntax error: '->'
1>H:\UnrealEngine\Engine\Source\ThirdParty\boost\boost-1_79_0\include\boost\core\pointer_traits.hpp(120): error C2238: unexpected token(s) preceding ';'
1>H:\UnrealEngine\Engine\Source\ThirdParty\boost\boost-1_79_0\include\boost\core\pointer_traits.hpp(123): error C2988: unrecognizable template declaration/definition
1>H:\UnrealEngine\Engine\Source\ThirdParty\boost\boost-1_79_0\include\boost\core\pointer_traits.hpp(123): error C2059: syntax error: '<end Parse>'
1>H:\UnrealEngine\Engine\Source\ThirdParty\boost\boost-1_79_0\include\boost\core\pointer_traits.hpp(123): error C2334: unexpected token(s) preceding '{'; skipping apparent function body

And then:

1>H:\UnrealEngine\Engine\Source\ThirdParty\boost\boost-1_79_0\include\boost\core\allocator_access.hpp(397): error C2988: unrecognizable template declaration/definition
1>H:\UnrealEngine\Engine\Source\ThirdParty\boost\boost-1_79_0\include\boost\core\allocator_access.hpp(407): note: see reference to class template instantiation 'boost::detail::alloc_has_allocate<A>' being compiled
1>H:\UnrealEngine\Engine\Source\ThirdParty\boost\boost-1_79_0\include\boost\core\allocator_access.hpp(397): error C2059: syntax error: '<end Parse>'
1>H:\UnrealEngine\Engine\Source\ThirdParty\boost\boost-1_79_0\include\boost\core\allocator_access.hpp(397): error C2334: unexpected token(s) preceding '{'; skipping apparent function body
1>H:\UnrealEngine\Engine\Source\ThirdParty\boost\boost-1_79_0\include\boost\core\allocator_access.hpp(398): error C2988: unrecognizable template declaration/definition
1>H:\UnrealEngine\Engine\Source\ThirdParty\boost\boost-1_79_0\include\boost\core\allocator_access.hpp(398): error C2059: syntax error: '->'
1>H:\UnrealEngine\Engine\Source\ThirdParty\boost\boost-1_79_0\include\boost\core\allocator_access.hpp(400): error C2238: unexpected token(s) preceding ';'

The second error repeats for every single template inside of allocator_access.hpp.

The only short-term fix I've found so far is to comment out all of the bimap includes in my project.

I am currently unsure of how to proceed and was hoping someone had some insight into what may be going on.

Answer 1

So, I found an answer. I'll share it here so that everyone can know:

In pointer_traits.hpp, the template has two functions:

        template<class O>
        static auto check(int)->result<decltype(O::pointer_to(source()))>;

        template<class>
        static char check(long);

I suddenly noticed the name: "check".

"check" is an Unreal macro name that forces Unreal Engine to crash upon invocation (unless a debugger is attached). Therefore, the function invocation that looked normal was instead being interpreted as a call to Unreal's check macro and causing compilation failures.

So I had to rename "check" throughout boost to something else. This fixed the compile errors, and my inventory system has been working again.