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From: kilgallen@eisner.decus.org (Larry Kilgallen)
Subject: Re: Apex vs GNAT on solaris
Date: 1999/12/08
Message-ID: <1999Dec8.103922.1@eisner>#1/1
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Date: 1999-12-08T00:00:00+00:00
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In article <384e52db.779218947@newsnew.draper.com>, rracine@myremarq.com (Roger Racine) writes:
> On Wed, 08 Dec 1999 06:35:08 GMT, Robert Dewar <dewar@gnat.com> wrote:
> 
>>In article <384cfdb3.691883075@newsnew.draper.com>,
>>  rracine@myremarq.com (Roger Racine) wrote:
>>> Many people will assume that the default options are the most
>>> reliable options.
>>
>>They will assume wrong. For example, in the case of GNAT,
>>we let -O0 be the default because that is traditional in
>>all gcc compilers. We make inlining off the default, because
>>that seems more compatible with -O0 as the default.
>>
> 
> That is a pretty questionable reason for creating a default.  Perhaps
> compiler documentation should state reasons for using the various
> options.  Of course, a given vendor might not want to say "turn
> optimization on only as a last resort, since it is not well tested",
> but certainly ACT (from what you say) should tell their users to turn
> it on.

Certainly compiler documentation should state the purpose of various
options.  I don't understand how, absent such a statement, one would
know that such an option exists.  Are there vendors whose documentation
says "we have an option called /FOOBAR, but we won't tell you what it
does" ?

>>They will assume wrong, there is no "best options", there is
>>only the appropriate options for your particular use.
>>
> 
> I do not know about your experience, but for me, with embedded system
> compilers (which tend to have comparatively few users compared to
> workstation compilers), for numerous languages over the years, it has
> always been dangerous to change the default optimization options.  ACT
> might want to reconsider their default.

I would believe Ada programmers to be a more discriminating bunch,
expecting features to have been tested, making incidents where an
adjustment to optimization options introduces "danger" to be less
frequent.  Furthermore, I would believe Ada programmers to expect
the vendor would fix anomolies encountered in this fashion.  Most
of all, I expect Ada programmers to test their resulting programs.
ACT might change their default, but misbehavior by other compilers
would be a silly reason to do so.

Larry Kilgallen