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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: GPS Compiler options
Date: Fri, 09 Apr 2010 22:00:58 +0100
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Date: 2010-04-09T22:00:58+01:00
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Ludovic Brenta <ludovic@ludovic-brenta.org> writes:

> Simon Wright wrote on comp.lang.ada:
>> Ludovic Brenta <ludo...@ludovic-brenta.org> writes:
>> > I think gnatmake -m corrects this problem. With this option, gnatmake
>> > no longer relies on the timestamps but only on the CRC32 values in
>> > the .ali files.
>>
>> I believe that it first compares the timestamps: if the same, no change,
>> but if different, does the ali check.
>
> Exactly. And gnatmake will then do the right thing (i.e. not
> recompile) if the timestamps are different only because the clocks of
> various machines are out of sync.

Indeed. But it takes much longer, because it has to open each file; and
this is even worse over a network.

GNAT 3.16a1 on Windows had a wonderful feature where the RTS timestamps
were out by an hour unless you installed in daylight savings time! This
led to opening all the relevant RTS files, every time, every
compilation -- and to an interesting work instruction.