Re: [gentoo-dev] ifc USE flag, fortran support and some general notes about multi-compiler support

[Anton Starikov <antst@ifm.liu.se>]

Donnie Berkholz wrote:
> This should be added to gcc-config, so it can support independent
> language compilers.
It is not compleet solution. Change everytime default compiler, if I 
understand correctly...not sounds nice.

> Yep. Some alternative compilers have their own configuration files for
> compiler-specific flags, however. They should still draw the generic
> flags from make.conf, such as CFLAGS, CXXFLAGS or FFLAGS (fortran).
Did you read correctly?  I whant to deal with two compilers at the same 
time. And it is really not excellent idea to froce them to use the SAME 
flags from make.conf. As example, -O3 is not really best for Intel 
compilers sometime. But can be goof enough for GCC. Ok, you can set 
IFCFLAGS on make.conf, but it is sollution for IFC ONLY.
Unfortunatelly, you have ONLY ONE set of flags for Fortran compiler 
(FFLAGS) in make.conf. :)

> Nah, USE isn't the right place for it. Ebuilds should respect the
> environment variables selecting compilers, such as CC, CXX, FC and so
> forth. The USE flags should be for other things, e.g. patches that are
> required for a specific compiler to work.
Again. they will respect SOMETIMES. But what if I want to use TWO 
compilers? Main and alternative at the same time? Should I change 
variables it every time?
I'm just speaking about adding some fucntionality for GENERAL 
alternative compiler. It can be used in some particular applications. 
Not everywhere. And such applications or libraries will try to compile 
with GENERAL alternative compiler. No patches for it. Just you own risk.
No changes in make.conf and environment variables each time when toy 
merge such applications.
Simple example. I really like to have fresh version of LAM-MPI in my 
developmnet machine. But I whant to build it with ICC and IFC. Nowdays 
if I have IFC and ICC and flags - it give me nothing. If I'm going to 
change my environmnet variables - I have to remove it from autoupdate 
and merge it manually, each time. With stetting these variables 
manually. Basically, it give ,me just nothing. it almost the same, like 
check is there newer version,  download tgz with sources, run configure 
and install manually.
Ok, I probably whant to use alternative compiler (GENERAL ONE) not for 
all ebuilds which support it. I can use /etc/portage/packages.use and 
I'm happy. It is pretty general thing if you doing some csience and 
dealing with fortran.

I really whant for me to have all near-scientific stuff to be compiled 
with alternative compilers, but NOT THE REST.

Do you really see currently something implemented to have such things in 
portage? I don't. So, I doing this almost manualy. I really can't leave 
it for emerge -u world. Because or it will try to compile with ICC and 
IFC, or with Lahey or with Absoft something that I don't whant to be 
compiled in such way.
Or it just compile everything with GCC and G77, and at morning I will 
find that my programs really don't want to be linked against MPI anymore :)

There is no currently support for GENERAL ALTERNATIVE COMPILER in 
gentoo. Which can be really helpfull in some situations.

I'm speaking about such mechanism.
I want to emerge -u world and be happy without doing a lot of things 
manually.
Or I want to bootstrap machine from scratch without siting near to it 
and handling all those things manually. I just want to give some 
configuration to portage that I want to have and go to do something else.

I really like gentoo. I use it for a two years. And OK, boostraping was 
nice. Updating was nice. Latter I handled all thing with near-scientific 
stuff manually on my home and office machines with different compilers. 
But latter my collegs start to be interesting from me to migrate from 
other distributions like Debian and mandrake to gentoo. And now they 
also have to deal with all this stuff. You know...basically me now have 
to deal with such stuff on their machines also, which is not greatest 
pleasure and time-spending.

If I understand correctly, gentoo  means freedom to have what you whant 
:) And I guess there is some, minor of course, part of gentoo users, 
which can be really happy with multi (or double) compiler support.
Again. There is no such functionality now in gentoo. It is really 
something new. Even normal support for use of ICC and GCC at the SAME 
TIME does not exist.

I can provide patches for some part of near-scientific ebuilds to 
provide such functionality. Because I anyway doing and mainteining such 
pathes now for me and my collegs. I really don't think that most of 
ebuilds need it. But for some it could be helpfull. Later probably it 
could be found that for a bigger number of ebuilds and users it is not 
so bad also to support it and people will support such support to other 
ebuilds.

At least I think there is something that could be discussed. Probably 
idea will changed after discussion.
But if I maintain already some extra fuctionality for gentoo for some 
people. I guess it is not so bad to maintain it for more, and I know 
that other people, who use gentoo for the same tasks will like it also.

Anton.

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