context::set_language does not correctly set __cplusplus

[martis42]

I am using wave as library in a tool which preprocesses C++ code to obtain some information and then lint it.
This requires preprocessing the code with a proper value for __cplusplus, as the code might use different #if .. branches depending on the value.

I know the C++ standard of the project. But I can't set __cplusplus myself because it is a special value which wave ignores when using the context::remove_macro_definition or context::add_macro_definition functions. This is fine, since the public API context::set_language exists.

However, I believe this API does not behave as expected:

• boost::wave::language_support::support_cpp14 does not exists, thus one cannot set __cplusplus accordingly
• boost::wave::language_support::support_cpp17 sets __cplusplus to 199711L, aka C++98
• boost::wave::language_support::support_cpp23 sets __cplusplus to 199711L, aka C++98
• boost::wave::language_support::support_cpp14 boost::wave::language_support::support_cpp26 does not exists, thus one cannot set __cplusplus accordingly. To be fair, C++26 is quite new and this point is more for completeness sake.

On the other hand, boost::wave::language_support::support_cpp, boost::wave::language_support::support_cpp11 and boost::wave::language_support::support_cpp20 cause __cplusplus to be set to the expected value.

I believe wave should offer a dedicated boost::wave::language_support::support_cppXX value for each released C++ version and set __cplusplus accordingly for preprocessing according to the values documented here

If you agree with the request I am happy to create a contribution for that.

[jefftrull]

That sounds very reasonable and I would welcome a PR. Thanks!

[jefftrull]

Update: the c++14 thing may be challenging, as we would need to separate out the associated features, which are currently lumped either under C++11 or 17, I can't remember which

[martis42]

Update: the c++14 thing may be challenging, as we would need to separate out the associated features, which are currently lumped either under C++11 or 17, I can't remember which

I believe The C++14 mode can be with respect to the associated features be a copy of C++11. It seems to me, C++14 simply did not ad new things to the language on preprocessor level. The things wave associates with C++11 and C++17 are correctly associated:

• Officially supporting files with a missing new-line at the end as added with C++11
• has_include was added with C++17