Re: [boost] [iostream] Boost should not be saying "_FPOSOFF"

Subject: Re: [boost] [iostream] Boost should not be saying "_FPOSOFF"
From: Edward Diener (eldiener_at_[hidden])
Date: 2016-09-06 16:32:59

On 9/6/2016 2:49 PM, Daniel James wrote:
> On 6 September 2016 at 19:24, Stephan T. Lavavej
> <stl_at_[hidden]> wrote:
>> [Rob Stewart]
>>> Can you tell us what change can be made to the code to effect what had been gained by using that macro?
>>
>> It's unconditionally:
>>
>> #define _FPOSOFF(fp)  ((long long)(fp))
>>
>> So you should be able to replace it with a static_cast, or eliminate it entirely.
>
> That might break older versions, or other uses of Dinkumware. I would
> try changing this configuration file so that it only applies to old
> versions:
>
> https://github.com/boostorg/iostreams/blob/develop/include/boost/iostreams/detail/config/fpos.hpp
>
> I don't have access to Visual C++ so I can't do it myself. If anyone
> wants to, all the relevant code is here:
>
> https://github.com/boostorg/iostreams/blob/develop/include/boost/iostreams/positioning.hpp

The best way for iostreams seems to be to create and use its own macro, 
equivalent to _FPOSOFF(fp), for older versions of VC++ but hardcodes as 
'((long long)(fp))' for VC++14 on up. This would allow Microsoft to 
remove it in future versions of VC++ without affecting iostreams. I 
assume Microsoft will not be retroactively removing for older versions 
of VC++ prior to VC++14, even if it is an implementation detail.

If iostreams is not currently under CMT, if you add it as a CMT library 
I will make the appropriate change and test it out. This won't get in 
1.62 but should be in the next release after that.