calling a C function from pgsql function

I have created a function in C language . This is to be called from a pgsql function .

Let say the C language function name is "test1" and pgsql function name is "test" .

test1 is called from test three times with different arguments .  For example :

test ()

begin

test1(arg1);    --test1 is a C library function  returning an int

test1(arg2);

test1(arg3);

end;

Now, my questions are :

1. what are the ways to get  the value returned by this library function . 

2. when test1 is called, will it wait for "test1" to return before continuing with the next statement in "test" or it will continue with the next statement parallely while "test1" is being executed.

3. Moreover, will test1  be called sequentially in order for all the three arguments i.e arg1 first and arg3 in last. Or there can be a different order.

Thanks..

Tamanna

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