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Date: Thu, 4 Dec 2008 14:35:02 -0500
From: "Gustavo Seabra" <gustavo DOT seabra AT gmail DOT com>
To: "Eric Blake" <ebb9 AT byu DOT net>
Subject: Re: gcc4/gfortran
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On Wed, Dec 3, 2008 at 8:36 PM, Eric Blake wrote:
> According to Gustavo Seabra on 12/3/2008 7:38 AM:
>> 1. Is is safe to remove the old gcc (3.*) packages and replace them by
>> symlinks to the new gcc4 executables?
>
> Read the archives.  Dave has mentioned that he is planning on a future
> packaging of the gcc packages that use the alternatives package, so that
> the symlink management of the name gcc can be done automatically to point
> to either gcc-3 or gcc-4.  But at the moment, I'm not sure whether the
> gcc-4 package requires files provided by the gcc package, in which case
> blindly deleting all thing gcc 3.* might break gcc-4.
>

Got it. But I was actually just planning on removing the gcc and g77
executables, and make those names point to gcc4 executables instead.

It actually has nothing to do with disk space: the whole point is
that, when compiling a program, I want to make sure it will *not* use
g77, but gfortran instead. The way it is now, I have to specify
gfortran-4 as the fortran compiler, say by using
FC=/usr/bin/gfortran-4, but one can never be sure exactly how a
specific 'configure' program will find its compilers. So, the removal
of gcc/g77 executables and replacing by a symlink would remove any
possibility for confusion.

>> 2. In this case, which executables should I point the symlink to? For
>> instance, if I were to replace g77 by a symlink to gfortran, which of
>> the 4 gfortran executables should I use:
>>
>>     $ locate gfortran | grep exe
>>     /bin/gfortran-4.exe
>>     /bin/i686-pc-cygwin-gfortran-4.exe
>
> These are identical copies; one is the name preferred when
> cross-compiling, the other when doing native compiles.

Got it, thanks.

> But why worry
> about adding symlinks?  Why not just rely on what the package gave you,
> since it works?  Are you really that low on disk space?  I suppose they
> could be made hardlinks to one another, if someone were to invest the time
> into patching setup.exe to attempt to make hardlinks (instead of its
> current behavior of blindly creating identical copies, even when the tar
> file specifies hardlinks).
>
>>     /usr/bin/gfortran-4.exe
>>     /usr/bin/i686-pc-cygwin-gfortran-4.exe
>
> These two are identical to the ones above - you need to read the manual,
> and remind yourself that /bin and /usr/bin are mount points that visit the
> same directory.  Removing /bin/gfortran-4.exe would simultaneously make
> /usr/bin/gfortran-4.exe disappear.
>
>>
>> 3. Lastly, just a dumb question: why do we get multiple executables in
>> the first place? I noticed that g77 also comes in multiple files:
>>     $ locate g77 | grep exe
>>     /bin/g77.exe
>>     /usr/bin/g77.exe
>>
>> Is that really necessary?
>
> Yes, because that's how the default mount points are set up.

OK, I had missed the point about /bin and /usr/bin actually pointing
to the same directory. Things are a lot clearer now.

Thanks,
-- 
Gustavo Seabra
Postdoctoral Associate
Quantum Theory Project - University of Florida
Gainesville - Florida - USA

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