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Subject: Re: [Boost-users] boost 1.47: gcc file dependency generation trips over BOOST_PARAMETER_MAX_ARITY
From: Dave Abrahams (dave_at_[hidden])
Date: 2011-09-17 02:34:43

on Thu Sep 15 2011, Ivan Le Lann <> wrote:

> ----- "Ytsen de Boer" <yrdeboer_at_[hidden]> a écrit:
>> Thank you for your answer.
>> I believe we are not on the same page.
>> Obviously, when I define the max arity to a value of 7 or more, the
>> preprocessor will finish properly.
>> But the point I am trying to make is more subtle, namely, that the
>> generation of the project dependencies has not a thing to do with the
>> boost max arity.
> I think it does actually.
> How could gcc track inclusions without preprocessing ?
> #ifdef USE_LIB_A
> # include "a.h"
> #else
> # include "b.h"
> #endif
> It seems very dangerous to me to use "-MMD" with different
> preprocessor definitions than at real compile time.
> But I'm not an expert.

Maybe not, but you've hit the nail on the head.

>> I don't know what the boost max arity means or what its for, but it
>> seems to me that it is a run time variable.

It couldn't possibly be a runtime variable. It's a preprocessor macro,
and runtime variables can't affect preprocessing.

Dave Abrahams
BoostPro Computing

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