Re: [boost] Header Inclusion practices

Subject: Re: [boost] Header Inclusion practices
From: Vicente J. Botet Escriba (vicente.botet_at_[hidden])
Date: 2017-04-11 19:23:35

Le 11/04/2017 à 19:55, Robert Ramey via Boost a écrit :
> As long as I can remember, it's been my practice to write program code 
> to minimize dependencies on the environment in which it is built.  By 
> environment I mean things external to the code itself like 
> environmental and command line variables, directory context etc.  As 
> part of this I use rules for header file inclusion:
>
> a) use #include "header.hpp" for files in the same directory as the 
> current source file.
>
> b) use #include "other directory/header.hpp" for files which are known 
> to be in a specific place relative to the current file. This shows up 
> in things like: #include "../include/header.hpp" for tests and examples.
>
> c) use #include <boost/serialization/xml_archive.hpp> for files which 
> are found by looking in directories listed in "-I" switches and 
> environmental variables (INCLUDE).  I generally try not to depend upon 
> any environmental variables as I always forget to set them or even how 
> to set them.  Come to think about it.  I don't know how my build 
> system finds the boost libraries.  I presume it's through some 
> IDE/Bjam/CMake setting which I can never remember.
>
> d) use #include <iostream> for standard library components. Presumably 
> these are routed to some directory relative to the compiler.
>
> So some of my source files look like:
>
> // interval.hpp header for safe numerics library
>
> #include <limits>
> #include <cassert>
> #include <type_traits>
> #include <array>
> #include <initializer_list>
>
> #include <boost/logic/tribool.hpp>
> #include <boost/core/demangle.hpp>
>
> #include "utility.hpp" // log
> #include "checked_result.hpp"
> #include "checked.hpp"
>
> and
>
> // example using he safe numerics library
>
> #include <iostream>
> #include <limits>
> #include <boost/integer.hpp>
>
> #include "../include/cpp.hpp"
> #include "../include/exception.hpp"
> #include "../include/safe_integer.hpp"
> #include "../include/safe_range.hpp"
>
> This has raised consternation in some quarters - but I don't see 
> anything wrong with it.  It basically means that only the <boost 
> libraries are depended on the whole b2 business.  I didn't want the 
> incubator version of the the safe numeric library to depend on the 
> library having been accepted into boost have have b2 run.  Also I 
> don't like adding the library to boost - and having to change all the 
> headers.  What if someone want's to run the tests/examples outside of 
> the boost tree.
>
> As far as I know this question has never been asked before and I'm 
> curious to know what others might have to say about this.
Hi,

Using

     #include "whatever.hpp"

disallows to check a .cpp file mocking the whatever.hpp file.

If you use instead

     #include <library ... path/whatever.hpp>

you can via your build system (-I option ) choose a diferent file 
located in a different folder that stubs, fakes or mocks the real file.

I you don't do such kind of test, then I would agree with Steven.

Vicente

Vicente