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To: cs551@merlot.usc.edu
Subject: Re: CS551 final1 - pass argument to threads
Date: Tue, 28 Oct 2008 07:44:18 -0700
From: Bill Cheng <william@bourbon.usc.edu>

Someone wrote:

  > When beacon create threads connecting to other beacons,
  > I use a for-loop which calls pthread_create and pass the iterator 'i'
  > into the thread as argument.
  > I found that created thread cannot get that argument correctly unless
  > wait for certain time, like 10ms.
  > For example, when i=3 and pass into thread#3. thread#3 may get 4 due
  > to for-loop increment that variable.
  > This looks like a bad way to use thread, but how to achieve my purpose?

Are you passing i by value or passing by reference?

You can actually pass i by value if that's what you want.
The last argument to pthread_create() is of type (void*).
So, if you just typecast i to (void*), you will copy the
value of i to the thread function.  If you don't like
typecasting to (void*), you can first typecast to (char*):

    (void*)(char*)i
--
Bill Cheng // bill.cheng@usc.edu <URL:http://merlot.usc.edu/william/usc/>