writing to a structure via pointer crashes...

This is a discussion on writing to a structure via pointer crashes... within the C Programming forums, part of the General Programming Boards category; Hi, i don't get why the following code crashes, please help! Code: #include <stdlib.h> #include <stdio.h> struct fifos { int ...

  1. #1
    Unregistered
    Guest

    writing to a structure via pointer crashes...

    Hi,
    i don't get why the following code crashes, please help!

    Code:
    #include <stdlib.h>
    #include <stdio.h>
    
    struct fifos
    {
        int *buf, in_cur;
    };
    
    typedef struct fifos fifo;
    
    void makefifo( fifo *fif, int amount )
    {
    
        fif->buf = ( int* )malloc( amount );
        fif->in_cur = 0;
    }
    
    main()
    {
        fifo *newfifo;
        makefifo( newfifo, 200 );
    }
    makefifo is supposed to create a fifo-stack with "amount" bytes, through a pointer to "newfifo"...

  2. #2
    Unregistered
    Guest
    ah, i'm stupid.
    Code:
    fifo newfifo;
    makefifo( &newfifo, 200 );
    ..is what it should look like.

  3. #3
    Registered User
    Join Date
    Sep 2001
    Posts
    752
    Traditionally, this kinda thing would be done with malloc...
    Code:
    fifo * makefifo(int amount )
    {
        fifo * fif;
        fif = malloc (sizeof (fifo));
        fif->buf = ( int* )malloc( amount );
        fif->in_cur = 0;
        return fif;
    }
    
    main ()
    {
     fifo * newfifo;
     newfifo = makefifo (200);
    }
    Callou collei we'll code the way
    Of prime numbers and pings!

  4. #4
    Unregistered
    Guest
    I thought about your version before, but i decided to take mine and i'm not going to change it for any "tradition" ;).
    Thanks anyway

  5. #5
    Unregistered
    Guest
    You may also want to allocate some memory for the fifos pointer...

    if you don't know why then you need to study more.

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