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From: agq@itd1.dsto.oz (Ashley Quick)
Newsgroups: comp.sys.apollo
Subject: Re: Apollo CC 5.7 Optimizer bummer
Message-ID: <1520@fang.dsto.oz>
Date: 10 May 91 01:06:43 GMT
References: <1991May8.231635.8782@emperor.scs.com>
Sender: news@fang.dsto.oz
Distribution: comp
Lines: 43

richd@emperor.scs.com (Richard Doherty) writes:


>I have a large program (that loads several other large libraries)
>that dies with a segmentation violation.  If I shut off the optimizer
>with the -dba flag, the program works flawlessly.  Apollo customer
>support could provide no clues.

>Question: Has anyone discovered optimizer problems?

Yes.

I have had a program which uses DOMAIN/OS mailbox calls,
and have had exactly the problem you describe. These calls
take a pointer to some storage, and fill that spot up with stuff.

With the optimiser on, the program (only about 50 lines long) crashes
with a segmentation violation. When off, works fine. I tried
the various different optimiser levels, and found that it broke
at levels 3 and above (I think... it was a year ago).

To add to HaPollos embarrasment, one of the domain
example programs used to break in the same way. (Dont know if
it still does... that was under SR10.1).

I tried: 1. Examine the assembler code from the C compiler. The
            optimiser puts lots of things into registers, and it
            was all so hard to follow I gave up.
         2. Compile the equivalent Pascal program with different
            levels of optimisation. They all worked fine.

Eventually, I gave up. I decided that the optimser did not matter
a lot to me!!!!!

No I have not reported this to HaPollo :-)



Regards...
Ashleigh Quick                             | ACSnet: AGQ@dstos3.dsto.oz
Defence Science and Technology Organisation| Internet: AGQ@dstos3.dsto.oz.au
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