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Date: Tue, 20 Aug 2013 10:02:44 +0800
Message-ID: <CAAWYfq3hc-dn4-2ATGjXuFf-phvEPfK6cdhTScuqhTnxCmUhKA@mail.gmail.com>
Subject: Re: g++-3 and g77-3 packages under setup-x86.exe
From: Dima Pasechnik <dimpase AT gmail DOT com>
To: cygwin AT cygwin DOT com
Cc: lmh_users-groups AT molconn DOT com
Content-Type: text/plain; charset=UTF-8

On 20 August 2013 03:13, LMH <lmh_users-groups AT molconn DOT com> wrote:
> I would be happy to build gcc-3 myself, I'm just looking for some
> documentation to get that done.
>
> The fact the gcc-3/g77 are old means nothing to me. There are still millions
> of lines of fortran77 code out there that are being used. There is just no
> reason to spend years of man hours to update the code and result in new code
> that gives the exact numerical answers as the old code. I already work 80,
> and sometimes even 100 hours in a week developing new material. The less
> time I have to spend on projects that already work as is, the better. The
> last time I checked, important linux distros used in industry (Cent, Suse,
> etc) all still included legacy gcc3 development support. If you think about
> the investment in gcc3 based code that is out there, and the time that could
> be required to port that to gcc4, keeping the legacy support makes allot of
> sense.
>
> When gcc4 first came out, I tried moving. I was able to get my code to
> compile and link after making allot of changes to the header files, but I
> got different numerical answers on my data for some cases. This is the real
> bugbear.

gfortran is not considered a bugbear since about gcc 4.1. Its
developers are committed to considering
any standard Fortran 77 code that does not compile or
gives wrong results on gfortran a bug.


> When you change compilers, everything has to be QC'd again. I tried
> again with gcc4.3, and found again that many header files had changed and it
> took quite a bit of work to get it to compile. When I did get it to work, I
> now got the same numerical answers as with gcc3. This underscores some of
> the issues that can happen when you change compilers, especially if the
> compiler is a relatively new version. Imagine some of the disasters that
> could have happened if I based research on the incorrect values from
> software compiled under the early versions of gcc4!!! There have also been
> allot of issues with folks trying to compile f77 code under gfortran.
>
> In many cases, there is just no good reason to move compilers when you have
> mature src code that has been optimized and QC'd for 30+ years. Why would
> you want to put ANY time into maintaining such code?

I used to write a lot of Fortran 4 code back in 198*ies...
Should I demand an IBM-360 Fortran 4 compiler being
distributed? :-)

> That is not a
> rhetorical question, so if there are some good reasons to move to newer
> versions of gcc, I would be interested in hearing the arguments. Putting in
> time to revise code and end up with the identical assembler is not something
> I am all that interested in.
>
Identical assembler? Come on, do you want your executables optimized for i486 ?
Then yes, you might want to us gcc3. :-)
Also it's obvious that most of Fortran 77 code had been developed not
on g77, but
using other compilers, mostly dead by now. After all, being a cross-compiler,
g77 is mostly a quick hack.

Dmitrii

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