Declare Function CondCreate ( ) As Any Ptr

result = CondCreate

A handle to a newly created conditional variable, or the null pointer (0) on failure.

Once the conditional is Condcreated and the threads are started, one or more of them can be set to CondWait for the conditional, they will be stopped until some other thread CondSignals that the waiting thread can restart. CondBroadcast can be used to restart all threads waiting for the conditional (including the main thread executing main program). At the end of the program CondDestroy must be used to avoid leaking resources in the OS.

''
'' make newly-created threads wait until all threads are ready, then start them all at once
''

Dim Shared hcondstart As Any Ptr
Dim Shared hmutexstart As Any Ptr
Dim Shared start As Integer = 0

Dim Shared threadcount As Integer
Dim Shared hmutexready As Any Ptr
Dim Shared hcondready As Any Ptr

Sub mythread(ByVal id_ptr As Any Ptr)
    Dim id As Integer = Cast(Integer, id_ptr)

    Print "Thread #" & id & " is waiting..."

    '' signal that this thread is ready
    MutexLock hmutexready
    threadcount += 1
    CondSignal hcondready
    MutexUnlock hmutexready
    
    '' wait for the start signal
    MutexLock hmutexstart
    Do While start = 0    
        CondWait hcondstart, hmutexstart
    Loop

    '' now this thread holds the lock on hmutexstart
    
    MutexUnlock hmutexstart

    '' print out the number of this thread
    For i As Integer = 1 To 40
        Print id;
    Next i
End Sub

Dim threads(1 To 9) As Any Ptr

hcondstart = CondCreate()
hmutexstart = MutexCreate()

hcondready = CondCreate()
hmutexready = MutexCreate()

threadcount = 0


For i As Integer = 1 To 9
    threads(i) = ThreadCreate(@mythread, Cast(Any Ptr, i))
    If threads(i) = 0 Then
        Print "unable to create thread"
    End If
Next i

Print "Waiting until all threads are ready..."

MutexLock(hmutexready)
Do Until threadcount = 9
    CondWait(hcondready, hmutexready)
Loop
MutexUnlock(hmutexready)

Print "Go!"

MutexLock hmutexstart
start = 1
CondBroadcast hcondstart
MutexUnlock hmutexstart

'' wait for all threads to complete
For i As Integer = 1 To 9
    If threads(i) <> 0 Then
        ThreadWait threads(i)
    End If
Next i

MutexDestroy hmutexready
CondDestroy hcondready

MutexDestroy hmutexstart
CondDestroy hcondstart

• Condcreate is not available with the DOS version / target of FreeBASIC, because multithreading is not supported by DOS kernel nor the used extender.
  
  

• Threading is not allowed in -lang qb
  
  

• New to FreeBASIC
  
  

• CondBroadcast
  
• CondDestroy
  
• CondSignal
  
• CondWait
  
• MutexCreate
  
• MutexLock
  
• MutexUnlock
  
• ThreadCreate