[fpc-pascal] The unfortunate deprecation of GetTickCount

Michael Van Canneyt michael at freepascal.org
Thu Apr 12 08:39:36 CEST 2018



On Thu, 12 Apr 2018, Graeme Geldenhuys wrote:

> On 2018-04-11 17:44, R0b0t1 wrote:
>> This is related to something I meant to propose a while ago related to
>> a cross platform timing and alarm API. 
>
> That already exists in the form of EpikTimer
> (https://github.com/graemeg/epiktimer). That is the latest
> implementation with the permission of the original author.

Ah, finally ! 
I was waiting for epiktimer to pop up in the discussion...

Thank you, Graeme :-)

> It uses the highest resolution timer it can find on each platform, and
> GetTickCount/GetTickCount64 as a fall-back

No, it doesn't. I just checked.

It uses clock_gettime if available on linux, otherwise it uses gettimeofday.

Maybe it used it at one point, but changed to a custom implementation to be
able to switch to clock_time ahead of FPC.

Also, it uses a cardinal in the linux version, so it will also have the wrap-around problem:

// Build a 64 bit microsecond tick from the seconds and microsecond longints
Result := (TickType(t.tv_sec) * NanoPerMilli) + t.tv_usec;

"Build a 64-bit microsecond tick" when result is a Cardinal ?
I don't think that can be right...

Note that TickType is a int64 (line 90 of the unit).

So, no use of systutils gettickcount, and a wrong implementation to boot...

I suggest fixing at least the bug.

Michael.


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