[boost] Libraries and C++ compliance

Subject: [boost] Libraries and C++ compliance
From: Edward Diener (eldiener_at_[hidden])
Date: 2017-04-10 02:24:51

I would like to ask people who present new libraries to Boost, in 
whatever stages they are, to please specify in the documentation to the 
library and/or in messages regarding the library, what level of C++ 
compliance is needed to use the functionality of that library. This plea 
is not being directed at any particular current library being mentioned 
by anyone on the mailing list, but is a general plea regarding 
developers and their efforts.

I realize it is a real pain that C++ as a language, and as it continues 
to evolve, has a number of popular levels of C++ compliance. This is 
largely because C++ is offered by a number of different vendors in a 
number of different supported releases, each particular implementation 
supporting a number of levels of C++ compliance and sometimes only 
partially supporting a particular level of C++ compliance. But given 
this sometimes difficult situation I do not see it as enough for library 
docs/information to simply say "this library supports 
some-vendor/some-release" because this is actually fairly meaningless to 
me when I know that "some-vendor/some-release" supports a number of 
levels of C++ compliance through some compiler parameter ( often 
-std=something ). Therefore docs/information of "the library supports 
"some-implementation" or "the library is compliant with "more than one 
level of C++ compliance" tells me as much as if some one told me that 
the moon is yellow. So I am begging, pleading, entreating library 
authors to be specific about the C++ features or the C++ level of 
compliance needed to use their library, even if it is just a one-liner 
that succinctly explains what the end-user needs to know.

Furthermore, for any given library could we please have specific 
information about what will happen if I use the library, or some feature 
of the library, without the desired minimum level of C++ compliance. 
While I would assume compile-time compiler errors as the norm another 
possibility, especially given the excellent support in Boost Config to 
compiler conformance, are more readable preprocessor errors. Finally a 
library might offer some level of advanced C++ compliance but fall back 
to a lower level if possible.

Please, please library authors this is important. No end-user or tester 
of your library wants to spend extended time trying to figure out why 
some compile fails when the answer turns out simply to be one of 
inadequate C++ conformance level for a particular compiler 
implementation being used with a particular level of conformance.