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POpthread_create function format and pointers - C Linux POSIX library
 

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  1. POpthread_create function format and pointers - C Linux POSIX library
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    <p>The question I have is, what exactly is the format of the pthread_create function and the function it calls, in terms of pointers and such? I can wrap my head around variable pointers, although I need to clarify my knowledge in that area, but function pointers get icky.</p> <p>I understand the preferred format is</p> <pre><code>void *threadfunc(void *arg); int main() { pthread_t threadinfo; int samplearg; pthread_create(&amp;threadinfo, NULL, threadfunc, &amp;samplearg); } </code></pre> <p>However, this generates a compiler warning that threadfunc's not returning a value, so apparently the * is something about what threadfunc returns, not a characteristic of the function?</p> <p>I have also seen the function defined as and the pthread_create formatted like such:</p> <pre><code>void threadfunc(void *arg); pthread_create(&amp;threadinfo, NULL, (void *)threadfunc, &amp;samplearg); </code></pre> <p>Which of these two are correct, or are they functionally equivalent? Could someone explain to me the mechanics of pointers to functions and such?</p> <p>One last question, would it work to, inside a for loop generating multiple threads, initialize an <code>int samplearg</code> for thread unique values then pass it to <code>pthread_create(...)</code>? I understand <code>samplearg</code> would be in scope inside the <code>threadfunc</code>, I'm just checking in case somehow C doesn't follow typical scope rules--since <code>samplearg</code> is created inside the <code>for()</code> loop and would typically go out of scope after the iteration of the <code>for()</code> loop, and the actual variable itself is being passed not the value. I'd test myself but there might be a point you could enlighten me on, and developing on a remote linux machine is a bit cumbersome for me.</p>
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    1. USj.i.h.
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    1. COpthread_create( ) returns an int. From the man page: RETURN VALUE If successful, the pthread_create() function shall return zero; otherwise, an error number shall be returned to indicate the error.
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      1. USPete Wilson
    2. CO@PeteWilson - he's not talking about the return value of `pthread_create()`
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      1. USBrian Roach
    3. CO@Brian Roach -- so he's not! thanks for the pickup.
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      1. USPete Wilson
 

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