Thread: free needed or not?

  1. #1
    Registered User
    Join Date
    Jan 2009

    free needed or not?

    hi every1,
    I use not-blocked tcp socket and i needed help with that..

    write(sock, (struct auth*)&autorization, sizeof(struct auth));
    r = read(socket_fd, recv, sizeof(recv));
    	for (i = 0; i < r; ++i){
    		if (.. /*checkout recv*/...){
                                   write(sock, &data, sizeof(data));
    		printf("Authentication fault\n");
    		goto exit;
    free(recv); // 1
    r = read(socket_fd, recv, sizeof(recv));
    // todo  smth...
    1) it's free needed or not? Because in the next if autorization was succesfull, that should do something.

  2. #2
    int x = *((int *) NULL); Cactus_Hugger's Avatar
    Join Date
    Jul 2003
    Banks of the River Styx
    Was recv returned to you from a call to malloc()? If so, yes. If it wasn't, then you probably shouldn't be calling free() on it.

    Also, will free() be called if the goto exit is taken?
    long time; /* know C? */
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    Any sufficiently advanced bug is indistinguishable from a feature.
    Real Programmers confuse Halloween and Christmas, because dec 25 == oct 31.
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  3. #3
    spurious conceit MK27's Avatar
    Join Date
    Jul 2008
    segmentation fault
    Is this a trick question?

    Quote Originally Posted by quantt View Post
    free(recv); // 1
    r = read(socket_fd, recv, sizeof(recv));
    Since read() does not allocate space, if recv is a pointer, this cannot be good. No you should not use free() there. Why do you want to?
    C programming resources:
    GNU C Function and Macro Index -- glibc reference manual
    The C Book -- nice online learner guide
    Current ISO draft standard
    CCAN -- new CPAN like open source library repository
    3 (different) GNU debugger tutorials: #1 -- #2 -- #3
    cpwiki -- our wiki on sourceforge

  4. #4
    Registered User
    Join Date
    Sep 2004
    Not to mention that if you are using sizeof(recv) in your code, chances are recv was not returned by malloc at all, and thus you do not need to free it.

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