Re: [boost] [Boost.Math] Re: [Monotone-debian] Bug#653764: FTBFS with Boost 1.48: lgamma_small.hpp:483:38: error: expected primary-expression before 'do'

Subject: Re: [boost] [Boost.Math] Re: [Monotone-debian] Bug#653764: FTBFS with Boost 1.48: lgamma_small.hpp:483:38: error: expected primary-expression before 'do'
From: John Maddock (boost.regex_at_[hidden])
Date: 2012-01-02 04:22:48

>> I'm not in a position to verify this for myself for another week, but
>> I have a horrible feeling I know what's wrong:  Monotone defines
>> several one-character macros for its own use, and L() is one of them.
>> It looks like Boost is using L() for its own purposes and expecting it
>> not to be a macro.
>
>Zack, you are absolutely right.  The lgamma_small header has a templated
>class method using "L" as one of the templates:
>
>template <class T, class Policy, class L>
>T lgamma_small_imp(T z, T zm1, T zm2, const mpl::int_<0>&, const Policy& 
>pol, const L&)
>
>The compile error at line 483 is at a call to L():
>
>      result = log(gamma_imp(z, pol, L()));
>

This isn't new to 1.48: the code has used "L" as a template param since at 
least 1.38.

>> I'd argue that Boost headers should take care to defend themselves
>> from the possibility of such macros, but fixing that in Boost might be
>> an enormous amount of work, and in any case, 1.48 is already out
>> there.

>Boost.Math developers: What is the right thing to do here?  More
>descriptive class template parameters?
>

That's what I'll use as a fix in this case, in general though, we can only 
fix "known issues" given that any symbol can be poisoned in the preprocessor 
:-(

Thanks for the heads up, John.