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Subject: Re: [boost] [mpl] Merging 'develop' to 'master'
From: Daniel James (dnljms_at_[hidden])
Date: 2014-03-20 18:39:16

On 20 March 2014 11:53, Edward Diener <eldiener_at_[hidden]> wrote:

> On 3/20/2014 6:00 AM, Daniel James wrote:
>> But also I object because I don't think that we can safely make
>> significant
>> changes to MPL. I recently discovered that a change to type traits had
>> broken several libraries, and no one noticed; changes to MPL have similar
>> problems. Our test results are a mess, and no one is monitoring a lot of
>> them, so updating libraries with lots of dependants is tricky.
> In this case we can't put out a Boost release if no one is monitoring test
> results for their library.

The problem is that many libraries don't have a maintainer. I suspect most
maintainers only check the test results periodically, possibly only when
they're making changes themselves.

I have been monitoring test results for MPL on 'develop' and none of the
> changes is causing any problems with the MPL tests.

I'm sure you're doing everything you can, but what I'm worried about is
problems that won't show up in the MPL tests. The overall tests results are
such a mess, that it's infeasible to get any idea about boost as a whole
from them, and new failures are easily missed.

Right now, I think the best approach to MPL is to only allow bug fixes.
> People doing metaprogramming are moving on to using C++11 features, which
> MPL doesn't serve particularly well, so I think we should be in the process
> of managing its decline, and be more concerned with old code that relies on
> it.

The changes made by Stephen Kelly got rid of support for VC6, VC7 ( VS2002
> ) and old versions of gcc ( prior to gcc-4 I believe ).

They remove support for some other compilers as well. We had an email from
someone who still uses Metrowerks which might have problems with the
partial template specialization changes.

I do want to update MPL at least with my fixes, so please tell me when you
> are finished cleaning up MPL's history.

You're watching the repo on github, so hopefully you should be notified
when I merge the pull requests. I'll probably merge them tonight anyway,
I'm just going to double check first. They should be okay, since they've
all been in either the develop or master for some time.

I think the best thing to do for MPL is to revert Stephen Kelly's changes,
and put them on a branch so that they can be reconsidered later. I'm not
saying they're bad - at the very least, removing support for old versions
of Visual C++ is a good idea. But I think we need to sort out the
libraries' dependants first. I'm going to try to start on some of these
soon, but it'll take a while.

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