Thread: shared memory array

  1. #1
    Registered User
    Join Date
    Sep 2012

    shared memory array

    I am getting a Segmentation fault(core dump) after i try to put my values into the shared array. Any Ideas?
    #include <stdio.h>
    #include <sys/shm.h>
    #include <sys/stat.h>
    #include <sys/types.h>
    #include <unistd.h>
    #include "Fib.h"
    int main(int argc, char *argv[]){
    int segment_id;
    int *shared_memory[10];
    const int size = 9096;
        segment_id = shmget(IPC_PRIVATE, size, S_IRUSR | S_IWUSR);
        printf("argc = %d", argc);
        pid_t pid;
        if(pid == 0){ 
            /*child process*/    
            /*writes child fib array*/        
            int fibArray[10];
            int value = 10;
            int j;
            int i;        
            for(i=0; i<value+1; i++){
                printf("\nChild %d", i+1);
                printf("= %d",fibArray[i]);
            /*child fib array ends*/
            /*writes the shared fib array*/
            int k;
                *shared_memory[k] = *shared_memory[k-1] + *shared_memory[k-2];    
                printf("\n%d", k);
            int l;        
            for(l=0; l<value; l++){
                printf("\nChild shared %d", l+1);
                printf("= %d", *shared_memory[l]);
            return 0;
        else if(pid > 0){ /*parent process*/
            int value = 10;    
            /*printf("\nPARENT: value = %d \n\n", value); /*LINE A*/    
            int i;        
            for(i=0; i<value+1; i++){
                printf("\nParent %d", i+1);
                printf("= %d",*shared_memory[i]);
            return 0;
        /*segment_id = shmget(IPC_PRIVATE, size, S_IRUSR | S_IWUSR);
        shared_memory = (int *) shmat(segment_id, NULL, 0);
        /*sprintf(shared_memory, "Hi there!");
        printf("*%s\n", shared_memory);*/
        /*shmct1(segment_id, IPC_RMID, NULL);*/
        return 0;

  2. #2
    TEIAM - problem solved
    Join Date
    Apr 2012
    Melbourne Australia
    Looks like your fibArray is going out of bounds
    fibArray[j] where j=10

    The maximum value allowed would be
    fibArray[j] where j=9
    Fact - Beethoven wrote his first symphony in C

  3. #3
    and the hat of int overfl Salem's Avatar
    Join Date
    Aug 2001
    The edge of the known universe
    > int *shared_memory[10];
    Try to explain what this is trying to do.

    You don't even initialise it before doing this
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.

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