Re: [boost] __COUNTER__ vs __LINE__

Subject: Re: [boost] __COUNTER__ vs __LINE__
From: Andrey Semashev (andrey.semashev_at_[hidden])
Date: 2012-01-11 14:06:03

On Wednesday, January 11, 2012 10:28:25 lcaminiti wrote:
> Hello all,
> 
> Many of Boost macro APIs PP_CAT symbols with either __LINE__ or __COUNTER__
> to make them unique (MPL_STATIC_ASSERT, SCOPE_EXIT, etc). AFAIK, __LINE__ is
> C++03 standard while __COUNTER__ is only a MSVC extension. I think using
> __COUNTER__ instead of __LINE__ might allow to expand a macro multiple
> times on the same line... but a  part from that:
> 
> What's the reason for using __COUNTER__ on MSVC instead of just using
> __LINE__ for all compilers?

MSVC has problems with expanding __LINE__ when precompiled headers are used. 
Basically, __COUNTER__ is the only practical option with this compiler when 
the macro is to be expanded in a header.