In general I want to avoid signed types for counts and sizes as then you have to consider both boundary conditions which is easy to mess up.

Comments URL: https://news.ycombinator.com/item?id=50153173

Points: 2

# Comments: 0

Your version expands `sum(1, 2, 3, 4, 5, 6)` to:

    sum(sizeof ((int []){0, 1, 2, 3, 4, 5, 6}) / sizeof *((int []){0, 1, 2, 3, 4, 5, 6}) - 1, ((int []){0, 1, 2, 3, 4, 5, 6}) + (sizeof ((int []){0, 1, 2, 3, 4, 5, 6}) / sizeof *((int []){0, 1, 2, 3, 4, 5, 6}) > 1))

    sum(6, (int[]){1, 2, 3, 4, 5, 6})

Whitespace is significant in the preprocessor so of course it tracks whitespace. Whitespace isn’t dropped until phase 7 when pp-tokens are converted to C tokens.

As I said it’s not impossible, write the patch and see if GCC accepts it.

Obviously this is possible, but no one has gotten around to implementing this feature and it’s not clear you would want either solution: buffering preprocessor tokens in case you need to expand a line for an error message greatly increases memory usage and the vast majority of compilations are successful ones with no errors, slowing down the normal case. And re-invoking the preprocessor to show you one line on every error message makes error reporting slow.

Comments URL: https://news.ycombinator.com/item?id=50106792

Points: 55

# Comments: 41

    #include 
    #include 
    void v(int y[printf("hello world!\n")]){ 
    }

    int main(){
        v(NULL);
        typedef int wut[printf("oh no\n")];
    }
    $ cc vla.c && ./a.out
    hello world!
    oh no