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Date: Mon, 19 Nov 2018 14:56:29 -0800 (PST)
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Subject: GNAT Modification_Time limitation
From: Lionel Draghi <lionel.draghi@gmail.com>
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Xref: reader01.eternal-september.org comp.lang.ada:54843
Date: 2018-11-19T14:56:29-08:00
List-Id: <comp.lang.ada>

I am coding a kind of make application, that depends on file's time tag (thanks to Ada.Directories.Modification_Time), and on Ada.Calendar.Clock, both returning Ada.Calendar.Time.

Unfortunately, I came across a GNAT limitation in the Modification_Time implementation on Linux : sub-second are ignored, and Modification_Time returns 
> Time_Of (Year, Month, Day, Hour, Minute, Second, 0.0);

So, at the same time Clock returns 2018-10-29 20:36:01.47
while Modification_Time    returns 2018-10-29 20:36:01.00

This prevents me from knowing if a file is modified before or after certain time, and thus undermine my efforts.

My workaround was to impair also Clock precision, with an ugly rounding:
> Time := Ada.Calendar.Clock;
> New_Time := Time_Of
>   (Year    => Year (Time),
>    Month   => Month (Time),
>    Day     => Day (Time),
>    Seconds => Day_Duration (Float'Floor (Float (Seconds (Time)))));

But that's not a correct solution either : I have to order lots of file creation, and having all files created during the same second returning the same time tag also prevent my algorithm from properly working.

Any workaround to get a precise file time tag? 
Or to compare file's time tag with Clock?

Thanks,

--
Lionel