Question

I have some questions about pthreads in linux:

1. Is it the case that pthread_t is it a datatype similar to int and char indicating we are defining a thread?
2. If so, how much size does it take? 2 bytes or 4 bytes?
3. Does the compiler allocate memory to pthread_t thread1 immediately after that statement or does it wait until it a pthread_create() call?
4. How does one set the thread attributes, and what is their typical use?
5. Can one only pass more than one argument in the pthread_create() call? If so, how?

I have lots of things on my mind like this. Please also feel free to suggest any good sites or documents to read.

Answer 1

Answering the questions one by one, though not necessarily in the same order:

Is pthread_t a data type similar to int or char, indicating we are defining a thread ? Does the compiler allocate memory to pthread_t thread1 immediately after that sentence or does it wait until it finds the pthread_create() call

pthread_t is a type similar to int and it’s created when you define it, not when you call pthread_create. In the snippet:

pthread_t tid;
int x = pthread_create (&tid, blah, blah, blah);

it’s the first line that creates the variable, although it doesn’t hold anything useful until the return from pthread_create.

How much size does a pthread_t take, 2 bytes or 4 bytes?

You shouldn’t care how much space it takes, any more than you should care how much space is taken by a FILE structure. You should just use the structure as intended. If you really want to know, then sizeof is your friend.

Any good information about how to set the thread attributes?

If you want to use anything other than default attributes, you have to create an attributes variable first and then pass that to the pthread_create call.

Can we only pass one argument in the pthread_create function to the function? Can’t we send 2 or 3 arguments in the pthread_create() function to the called thread?

While you’re only allowed to pass one extra parameter to the thread , there’s nothing stopping you from making this one parameter a pointer to a structure holding a hundred different things.

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If you’re looking for information on how to use pthreads, there’s plenty of stuff at the end of a Google search but I still prefer the dead-tree version myself: