Re: [boost] C++03 / C++11 compatibility question for compiled libraries

Subject: Re: [boost] C++03 / C++11 compatibility question for compiled libraries
From: Edward Diener (eldiener_at_[hidden])
Date: 2018-02-08 15:28:51

On 2/8/2018 9:20 AM, Peter Dimov via Boost wrote:
> Edward Diener wrote:
> 
>> As far as which library to use, depending on the compiler/version 
>> available, either boost or std, of two very similar libraries, this is 
>> what my Cxx_dual library (https://github.com/eldiener/cxx_dual) is all 
>> about.
> 
> That's not going to work at all if link compatibility is desired. If you 
> have
> 
> class something
> {
> private:
> 
>  Â Â  CXXD::function<void()> f_;
> 
> public:
> 
>  Â Â  // ...
> };
> 
> the layout of `something` changes between C++03 and C++11, which leads 
> to incredibly nasty things at runtime as objects appear at the wrong 
> address and the observed behavior makes no sense.

I discuss a solution for this in the documentation topic "Use in a 
non-header only library".

> 
> I inadvertently introduced such a problem in Boost.System when I made 
> the object layout dependent on whether <system_error> was available, to 
> enable conversions from/to std::error_code. It's not fun at all. (I have 
> since fixed that, and added tests that link to the library from a 
> forced-03 or forced-11 main.cpp. Incidentally, the layout of std::string 
> also changes between 03 and 11, so if such compatibility is desired, you 
> can't use that either.)
> 
> (But there's absolutely no need to use std::function "for std::bind 
> compatibility". boost::function can store std::bind just fine (and vice 
> versa.))