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Question on C syntax

This is a discussion on Question on C syntax within the C Programming forums, part of the General Programming Boards category; hi, I came across this code online on a tutorial site. This part of the code confused me. Code: /* ...

  1. #1
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    Question on C syntax

    hi,
    I came across this code online on a tutorial site. This part of the code confused me.

    Code:
    /*
     * parse--split the command in buf into
     *         individual arguments.
     */
    parse(buf, args)
    char *buf;
    char **args;
    {
        while (*buf != NULL) {
            /*
             * Strip whitespace.  Use nulls, so
             * that the previous argument is terminated
             * automatically.
             */
            while ((*buf == ' ') || (*buf == '\t'))
                *buf++ = NULL;
    
            /*
             * Save the argument.
             */
            *args++ = buf;
    
            /*
             * Skip over the argument.
             */
            while ((*buf != NULL) && (*buf != ' ') && (*buf != '\t'))
                buf++;
        }
    
        *args = NULL;
    }
    What confused me was the local variables declared ouside the opening brace of the function definition. I have also seen such code before once but thought it was a typo. But obviously this is a valid syntax. Can someone clear this for me please.

    -Livin

  2. #2
    and the hat of wrongness Salem's Avatar
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    Yes, that is K&R syntax for declaring a function (pre-dates ANSI-C).
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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  3. #3
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    Salem is correct. Depending on the material you're reading, you may see them more often than you might have expected. Anyway, it's really just the old way to define a function:
    Code:
    parse(buf, args)
    char *buf;
    char **args;
    {
        /* code here */
    }
    is the same as
    Code:
    int parse (char *buf, char **args)
    {
        /* code here */
    }
    If you don't see a return type, it is automatically int. That's really the only nuance of the syntax that could make it difficult to understand in my opinion.

  4. #4
    cas
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    This may be obvious, but you do not want to use the K&R style functions in new code. K&R declarations are not prototypes, so the compiler cannot check to make sure you're calling a function properly. If you try to provide a prototype for a K&R style function, problems will occur with certain types (_Bool, char, short, and float) due to promotion issues.

    In short, knowing K&R style is good for reading old code, but it should never be used in new code.
    Salem likes this.

  5. #5
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    Thank you all. I was almost convinced I had some basic concepts missing. Now it makes sense.

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