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Subject: Re: [boost] Single letter template type causes errors in compile of program_options and filesystem boost libraries
From: OvermindDL1 (overminddl1_at_[hidden])
Date: 2008-12-18 17:38:25

On Thu, Dec 18, 2008 at 3:32 PM, OvermindDL1 <overminddl1_at_[hidden]> wrote:
> On Thu, Dec 18, 2008 at 3:09 PM, Mike Collier <mcollier69_at_[hidden]> wrote:
>> Thanks for the suggestions.
>> On Dec 18, 2008, at 1:37 PM, Beman Dawes wrote:
>>> On Thu, Dec 18, 2008 at 3:51 PM, Andrey Semashev
>>> <andrey.semashev_at_[hidden]> wrote:
>>>> Stefan Seefeld wrote:
>>> ...
>>>>> Sorry, but this is just bad coding practice. Instead of changing boost
>>>>> in
>>>>> order to accomodate for it, I suggest that you isolate the libraries
>>>>> from
>>>>> each other, by carefully undefining those single-letter macros prior to
>>>>> including boost.
>>>> Another solution might be simply changing include order, so that boost
>>>> headers get included prior to the vendor-provided headers.
>>> It might be better not include the vendor-provided headers at all,
>>> since it would not be surprising if these headers had many other
>>> additional problems. Better to provide a modern, safe interface via
>>> your own headers, implemented in an isolated translation unit that
>>> calls the vendor's functionality.
>> It's not really to practical to leave out the vendor header because the
>> defines are used a lot in code. Not using them would give incorrect results
>> or cause the compile to fail in code written such as this
>> voltage = 10 V;
>> current = 100 uA;
>> where uA is :
>> #define uA *1.000000e-06
>> These are connivence ( or I might say crutch ) defines for electrical
>> engineers who don't want to code with proper exponents or want a little
>> documentation in the code. I know this is a bad practice but it's in a
>> header that's vendor supplied and these connivence defines are used in lot's
>> of code.
>>>>> If something should use longer names, it's these macros in your library,
>>>>> not boost template parameters.
>>>> Since this library is not Mike's, I'd rather suggest reporting this issue
>>>> to
>>>> the library vendor.
>>> Yep. One wonders what they could have been thinking and why they used
>>> macros rather than something that observed scoping.
>> The vendor ( Verigy ) is not known by people who use their software as
>> having good software so it's not surprising to me they coded their macros
>> this way. They probably thought it would be nice if non-programmer
>> electrical engineers could use units next to numbers to save time or make
>> code self documenting. I doubt they would be willing to change the header
>> since it's used around the world in legacy code that would all fail the
>> compile or worse compile and give incorrect results.
>> My solution is to change type names in the boost headers , since I can
>> control these locally and I don't see any benefit to using short names in
>> the boost headers. My ideal solution would be for the boost headers to use
>> longer names to start with.
>> Any other ideas are welcome.
> The thing is, the names in the boost headers are used as typenames,
> meaning that even if those were used as type or variable names
> anywhere else, it would not interfere at all. Those headers you use
> are using macros, which, to be blunt, is a rather stupid thing to do.
> If you wanted to enforce types between the electrical types, then
> Boost.MPL could make something like that quite easily (it is one of
> the example usages even), would be both self-documenting and type-safe
> (unlike their current broken macro defines that do nothing but cause
> problems). I do not think the Boost ones should be changes because,
> as stated, they are used as internal types that would mess with
> nothing else at all if other programmers were half intelligent.
> But why not, as was stated before, just include the boost header
> *before* you include the broken header?

Or, make a wrapper header and just have undefine those if set, include
the boost headers, then redefine them if they were defined before?
Also quite easy.

And here is the Boost.MPL page of exactly that kind of example; it
would give them their self-documentation, as well as being typesafe,
as well as helping to make sure the programmer cannot screw up and
start multiplying things together that they should not do and so forth
(would throw a compile error, you know, instead of their internal
logic silently breaking down):

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