Thread: prototype

  1. #1
    Wanabe Laser Engineer chico1st's Avatar
    Join Date
    Jul 2007


    When people give a prototype,

    ie/ rval foo(Int32 val, Int32 *val2)
    Is it supposed to be what I am passing into the function or what the first line of the function looks like?

    like is it

    >>function foo(Int32 val, Int32 *val2){

    int main(void){
    >>foo(Int32 val, Int32 *val2)

  2. #2
    Woof, woof! zacs7's Avatar
    Join Date
    Mar 2007
    > ...what the first line of the function looks like?
    By that you mean the function definition? Then yes, that's correct.

    int foo(int val, int * val2);
    int main(void)
        int test = 5;
        int b = 10;
        foo(test, &b);
    int foo(int val, int * val2)
        /* do something */
        return 0;

  3. #3
    Cogito Ergo Sum
    Join Date
    Mar 2007
    Sydney, Australia
    prototypes end in semi-colons

    It declares the function for the compiler to look for or something like that

    It is also declares the types and the names of the variables that you will be passing into when you call it

    If you prototype a function like

    int hi (int a, char *v);
    you can call it like
    You can change the variable name too when you are calling it
    as long as the types match.

    Then the function itself and what it does must be coded, in this example since it is int it must return a type of int

    int hi (int a, char *v) {
    return 0;
    Last edited by JFonseka; 05-26-2008 at 06:49 AM.
    Everytime you segfault, you murder some part of the world

  4. #4
    Join Date
    Oct 2007
    Inside my computer
    The prototype specifies what type of arguments a function takes and what it returns - nothing else (hence the compiler doesn't care which arguments you pass to the function, as long as the types match what the function expects).
    The compiler uses that information to generate code to call your function.
    Oh and make the definition and the prototype match, because the compiler will prioritize the prototype and if it compiles (usually it doesn't), then you will get bad things(TM).
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

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