CODEWITHSUNDEEP
.netvb.netconsole-application
Mad Dog Tannen
Mad Dog Tannen

Reputation: 7242

Infinite loop in Sub Main() by calling itself?

This might be a really stupid question and im looking for your input if this is a bad/good/forbidden approach.

Lets just say i have a console application that i want to run forever.

I just tested this

Module Module1

    Sub Main()
        Try
            Console.WriteLine(Now())
            System.Threading.Thread.Sleep(1000)
        Catch ex As Exception

        End Try
    ' Call the routine again
    Main()
    End Sub

End Module

This simply prints the current time after sleeping 1 second and will continue to run.

I just want to know if this is a ok or bad way of looping a routine?

Upvotes: 2

Views: 600

Answers (3)

Aaron Palmer
Aaron Palmer

Reputation: 9022

Running an infinite loop in a console app is definitely a bad idea. As Roger Rowland stated, it will result in a stack overflow.

If you want something to always be running in the background you could use a Windows Service instead of a console app.

If you need to use a console app, because Windows Services aren't available on all platforms (ie. Compact Framework), you could try this.

Upvotes: 1

Hans Passant
Hans Passant

Reputation: 942488

It depends on what machine you run this on. If it boots a 64-bit operating system and your project's Target CPU setting is "AnyCPU" then it will work okay, the 64-bit jitter will use an optimization called "tail recursion optimization" to turn the recursive call into a jump. If not then your program will eventually bomb with this web site's name.

No point in taking that risk when you can do this:

Sub Main()
    Do
       '' Rest of your code
       ''...
    Loop
End Sub

Upvotes: 2

Roger Rowland
Roger Rowland

Reputation: 26279

This is infinite recursion and will eventually result in a stack overflow.

Every time you call a function, stuff is pushed on the stack. As each function finishes, the stack "unwinds" by popping that stuff off. You're never finishing any function and the stack has a limited size. Eventually you will exceed that size and you will crash.

Remove the sleep and see what happens.

Upvotes: 1

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