Programming

I see there is a problem with the memory segment size that you allocate, and then try to use memory beyond that size. The shmget statement creates segment of size sizeof(buffer[2]) - two problems here
a) array buffer is declared buffer[2], so there are two elements in it, buffer[0] and buffer[1],
b) I guess you meant t oallocate segment to accomodate array buffer - just say sizeof(buffer) in your shmget statement

Then again later you are placing result of computation into buffer[2] - same problem as above.

Remember in C array element counts start with 0, so any array A(N) has element A[0], A[1], ... , A[N-1], there is no A[N]

yes but also if i use buffer[3] instead buffer[2], return same error, i have already thought that was an error of memory segment, but if i try all possibilities.
if i use IPC_CREAT i've same error and also if i use nothing i've same error. why?

---------- Post updated at 03:37 AM ---------- Previous update was at 02:21 AM ----------

i've change dimension of buffer...and i do a test for every system call and now it gives error on shmdt system call, it says "Invalid Argument"
why?

if you are trying to access buffer[3] make sure the array is declared with saze of at least 4, that is

Code:

int buffer(4);

nothing also with buffer[4] i've same error on output...

no one can help me?

You agreed not to bump posts here when you registered.

I've been busy. I'll take another look at it now that I'm not busy.

Your semaphore obviously didn't work,at all, ever, and I'm not sure how to fix it.

[edit] some updates:

Code:

    if (figlio==0){
        execvp("./adder","./adder", NULL);
        a=point[2]; // THIS CODE WON'T EVER BE EXECUTED
        fflush(stdout); // NEITHER WILL THIS
        exit(0); // NEITHER WILL THIS
    }

execvp replaces the current program. It's not like system().

You need to wait() for the child in the parent to finish instead, then get the value from point[] yourself.

execvp required only two argument...