Compiling boost with MSVC2015 with /std:c++latest (or C++17/N4190)

Question

When I try to build boost with MSVC2015 with the /std:c++latest flag I get an error:

boost\algorithm\string\detail\case_conv.hpp(33): error C2143: syntax error: missing ',' before '<'

Which points to:

 // a tolower functor
 template<typename CharT>
 struct to_lowerF : public std::unary_function<CharT, CharT>

Now this seems to be due to N4190 as mentioned here: https://www.visualstudio.com/en-us/news/releasenotes/vs2015-update3-vs

/std:c++latest also controls the removal of the following old features: N4190 "Removing auto_ptr, random_shuffle(), And Old Stuff", P0004R1 "Removing Deprecated Iostreams Aliases", LWG 2385 "function::assign allocator argument doesn't make sense", and various non-Standard features (the std::tr1 namespace, some TR1-only machinery, and the std::identity struct).

When using:

 std::string a,b;
 return boost::iequals(a,b);

And using boost::ilexicographical_compare.

Its also mentioned here:

https://blogs.msdn.microsoft.com/vcblog/2015/06/19/c111417-features-in-vs-2015-rtm/

Stephan T. Lavavej - MSFT

Azarien: Removing auto_ptr/etc. will have positive consequences. It will prevent new code from using outdated/complicated/unsafe

machinery, and it will reduce confusion among non-expert users. (For example, unnecessary unary_function/binary_function inheritance is common, because many users thought that STL algorithms/containers required this, when in fact only the outdated adapters did.) And auto_ptr in particular is unsafe, because its mutating "copy" constructor silently moves from lvalues.

So how do I get boost to compile with VC2015's /std:c++latest? Right now it appears boost isn't C++17 compatible?

Answer 1

Define the macro _HAS_AUTO_PTR_ETC before including any headers. For your own code, if you're using Visual Studio's build system, this is best accomplished by way of your project's Preprocessor Definitions setting. For building Boost itself, add define=_HAS_AUTO_PTR_ETC to your b2/bjam invocation.

Other previously-standard functionality implicitly disabled by /std:c++latest can be controlled by defining the macros _HAS_FUNCTION_ASSIGN, _HAS_OLD_IOSTREAMS_MEMBERS, and _HAS_TR1_NAMESPACE. These macros are all outlined in the following blog articles:

STL Fixes In VS 2015 Update 3
VS 2015 Update 2’s STL is C++17-so-far Feature Complete