Re: [PATCH 2/2] gnu: Add Mlucas.

[Alex Vong <alexvong1995@gmail.com>]

Hi,

Sorry, the following reply is written in a spaghetti-style (lots of
gotos) , please be patient :)

On 07/11/2015, Andreas Enge <andreas@enge.fr> wrote:
> Hello!
>
> I must admit I was put off looking at this patch by the addition of the
> flags system, of which I do not understand the justification. Basically,
> it seems to be an additional layer on top of what we already have in
> our different build systems. We have #:configure-flags and #:make-flags,
> and in extreme cases we can set environment variables such as CPPFLAGS
> and so on in an additional phase. Commonly used flags can be added to the
> build systems once and for all, for others, my impression is that we
> already
> have the mechanisms for doing it on a per package basis. Which problem does
> this part of the patch solve?
>
The idea comes from dpkg-buildflags
<http://manpages.debian.org/cgi-bin/man.cgi?query=dpkg-buildflags&apropos=0&sektion=0&manpath=Debian+unstable+sid&format=html&locale=en>.
It exports a selectable sets of build flags which are useful for
almost all packages. For instance, stackprotectorstrong protects your
program from stack smashing. For more detailed explanation, you can
see <https://lists.gnu.org/archive/html/guix-devel/2015-10/msg00079.html>.
I am adding this because I think Guix doesn't have a way to retrieve a
sets of common build flags. You are right that, currently, this only
works for gnu build system, are you proposing this should be in
`guix/build-system/gnu.scm` instead since this is
gnu-build-system-specific? I think "Commonly used flags can be added
to the build systems once and for all" doesn't always work. Some flags
will break the build for some packages, and the easiest fix is to turn
it off. So there should be a way to select the right subset of flags
that works for you instead of having a list of essential build flags.
The aim is to make it easier for packagers to retrieve the right
subset of useful (e.g. security-related) flags that works, *hopefully*
making the binary more secure.

> On Mon, Oct 26, 2015 at 12:34:59PM +0100, Paul van der Walt wrote:
>> > * gnu/packages/mlucas.scm: New file.
>> I'm not an expert, and i'm not 100% sure on this so it's an honest
>> question, but does this application really deserve a new package file?
>> Shouldn't mlucas perhaps be added to maths.scm?
>
> It should go to algebra.scm, which regroups tools of symbolic, exact
> computation (whereas maths.scm contains tools for numerical computation).
>
Mlucas does numerical computation (it makes use of FFT to find
Mersenne primes!), not symbolic, so it should be fine staying in
`maths.scm`.

Thanks for the review!

> Andreas
>
>
Cheers,
Alex