GetTickCount - Ouch!

[cafeenman]

When you find out that a function that 95% of your code relies on craps out after 24ish days.

I didn't know it worked like that.

The nuts and bolts of it is that my program throws up random events.

An early problem was sometimes it would throw up the same random event a very short time to the last time.

So I put timers in them to indicate how long they had to wait before they could occur again. If it got called before that it skipped out.

Then ALL events suddenly stopped working in my program at the same time.

When I checked it, I found that GetTickCount was return -2 billion something or other.

What that meant was that every event called skipped out because the interval was less than the requirement.

I've fixed it but wow... it's all over my code and now a lot to fix.

In 30 something years of VB6 I've never run into this before. But I don't think I've ever run any of my code for 24 days straight either.

Offending Code:

Public Property Get EventElapsedSeconds(ByRef EventStartingTicks As Long) As Double

EventElapsedSeconds = CDbl((GetTickCount - EventStartingTicks)) / 1000

End Property

Example of how it was called:

Private Function Random05() As Long
Static nTickcount As Long

If EventElapsedSeconds(nTickcount) < 60 Then Exit Function

ShowGamePlayNotes

nTickcount = GetTickCount

End Function

The nice thing about that code was that I could return fractions of a second. That didn't come up often but there are a few cases.

So my fix won't have the GetTickCount problem but it only returns whole seconds (I think).

Public Property Get ElapsedSeconds(ByRef FromDate As Date) As Double

If (FromDate = "00:00:00") Or (FromDate > Now()) Then FromDate = Now() ' FromDate is not Initialized.

ElapsedSeconds = DateDiff("s", FromDate, Now())

End Property

Called as thus:

Private Function Random05() As Long
Static dLastEvent As Date

If ElapsedSeconds(dLastEvent) < 60 Then Exit Function

ShowGamePlayNotes

dLastEvent = Now()

End Function

[fafalone]

Much easier way as long as you're not still supporting XP: Use GetTickCount64. Substitute Currency for ULONGLONG.

[cafeenman]

Well... unfortunately, I've converted most of my code now and it took days to do.

But I've been keeping versions so I can try that in an earlier version and see how it works.

Does it do the same thing (return a negative number) after a billion days or something?

[passel]

It would be 24 days * 2 billion, i.e. around 48 billion days or around 132 million years. Most people aren't worried about their programs needing to run that long.

[baka]

Function ElapsedSeconds(Optional ByVal FromSeconds As Currency) As Currency
    Dim CurrentTick As Currency

    CurrentTick = CCur(GetTickCount())

    If CurrentTick < FromSeconds Then
        ElapsedSeconds = (2 ^ 32) + CurrentTick - FromSeconds
    Else
        ElapsedSeconds = CurrentTick - FromSeconds
    End If
End Function

[cafeenman]

I like that one. It will return fractions of seconds.

So while researching this, I came across something that said that GetTickCount resets itself to a positive integer (long) after something like double the days it takes to crap out.

E.g. in 49ish days it's back to normal.

Anyone know anything about that and can shed light on it?

[baka]

in VB6 GetTickCount will converts into signed LONG, 0-2147483647 and -2147483648-0 and after that reset to 0 and start over.
unsigned LONG would be 0-4294967295 and after that reset to 0.

the function I shared works within 49 days. so surely if the FromSeconds is above that it will not work.

[cafeenman]

OK, by my estimates, it will take over 100 days to complete the game if it runs non-stop.

I'm not sure because I've never actually completed a run.

But I'm up to 24 days.

[fafalone]

I'm over it...

Days : 106
Hours : 17
Minutes : 20
Seconds : 28
Milliseconds : 495
Ticks : 92208284950457

32bit tick count is 634583439 (7d 8h) so yeah it got back to zero a week ago.

[cafeenman]

It would be 24 days * 2 billion, i.e. around 48 billion days or around 132 million years. Most people aren't worried about their programs needing to run that long.

True, but it's possible. So I want all my bases covered.

[HackerVlad]

Write the GetTickCount64 function declaration

[fafalone]

Declare Function GetTickCount64 Lib "kernel32" () As Currency

or in tB
Declare PtrSafe Function GetTickCount64 Lib "kernel32" () As LongLong
so you don't have to deal with stupid Currency (though of course tB supports it too)

[HackerVlad]

Thank you. But a minimum of windows vista? Won't it work in Windows XP?

[HackerVlad]

And how many days will the counter last? Continuously, how many days or how many years will it take before the failure?

[2kaud]

Thank you. But a minimum of windows vista? Won't it work in Windows XP?

In each version of Windows, MS introduce new API's. Obviously these will only work in the versions in which they are supported. They won't work - because they are not implemented - in earlier versions. So if a particular API only works with Vista and later then it was introduced in Vista and so isn't available in previous window versions (eg XP). The converse is also sometimes true. Already implemented API's can be removed in later windows versions - so any code that uses these will only work with previous windows versions. If you need code that uses functions available only with certain versions then it's usual (at least in c code) to use compile-time conditions and run-time checks to determine which parts of the code are compiled for which windows versions. For different windows versions this could be a simple message box saying a facility is not available for that version or alternative code to provide the missing function in a different way.

[Zvoni]

I don't understand why everyone is so surprised.
Just read the documentation:
https://learn.microsoft.com/en-us/wi...i-gettickcount

DWORD GetTickCount();

Retrieves the number of milliseconds that have elapsed since the system was started, up to 49.7 days.

The "half" of 49.7 days IS about 24 Days, since you don't have an unsigned 32-Bit Integer in VB6

https://learn.microsoft.com/en-us/wi...ows-data-types
DWORD = A 32-bit unsigned integer. The range is 0 through 4294967295 decimal.

QueryPerformanceCounter/-Frequency-Combination might be more reliable