[Boost-build] Ping: Re: [pch] gcc woes

From: Johan Nilsson (r.johan.nilsson_at_[hidden])
Date: 2007-10-08 08:11:23

Ping?

Johan Nilsson wrote:
> Vladimir Prus wrote:
>> On Friday 05 October 2007 10:25:03 Johan Nilsson wrote:
>>> Hi,
>>> 
>>> after attempting to use precompiled headers toghether with gcc
>>> 4.1.2, I figured I might as well post my "findings" here.
>>> 
>>> Pre-4.2.0 gcc can't handle pch and anonymous namespaces in headers,
>>> ref: http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29085
>>> 
>>> This makes it virtually impossible to use pch toghether with e.g.
>>> Boost.Lambda, Boost.Parameter to build programs with multiple
>>> translation units.
>>> 
>>> Perhaps a note of this could be added to the BBv2 pch docs?
>> 
>> Possibly, thanks for letting know.
> 
> Also, it seems like the base name of the pch header needs to be
> exactly the 
> same as the pch target name. Does the provided example (in the docs)
> really 
> work?
> 
>> 
>>> 
>>> Also - is it possible to disable pch using conditional requirements,
>>> making the pch rule effectively returning a "null" target?
>> 
>> The <pch>off feature will have that effect.
> 
> Thanks. However, adding <toolset>gcc:<pch>off to my root project
> properties 
> caused everything to rebuild as /pch-off/ was added to the target
> paths. Not 
> much to do about it I guess, but annoying nevertheless.
> 
> Is there possibly a way to obtain the effect of the imagined
> conditional requirement
> "<toolset>gcc,<toolset-version-below>4.2.0:<pch>off" without 
> resorting to indirect conditional requirements?
> 
> One final point: Inside the pch target definition, I also setup the
> path to 
> the pch header as an <include> requirement as I have multiple levels
> of 
> source directories within the project. As a result of this, when
> turning off 
> pch, the source files fails to compile (they no longer find the
> actual pch 
> header file).
> 
> Do you have any suggestions for how to handle the above in a generic,
> clean 
> way?
> 
> / Johan
> 
> 
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