Fixes for minor issues

[daniloegea]

Description

Some of this issues were found when I tried to compile netplan as c++, some were found by increasing the warning level with -Wextra and some were found by me while fixing the issues found by the compiler.

Some changes might seem unnecessary, specially the one annotating unused parameters with __unused. But I think they add some value.

My motivation to increase the warning_level to 2 is to avoid problems like this:

int main() {
    int a = -1;
    unsigned int b = 1;
    if(a > b) {
        printf("According to my calculations %d IS greater than %d\n", a, b);
    }
}

$ cc main.c
$ ./a.out
According to my calculations -1 IS greater than 1

It's unfortunate that it's only caught by the compiler by using -Wextra or explicitly using -Wsign-compare (which is enabled by -Wextra).

Annotating the unused parameters with __unused at least makes us aware about the big number of function parameters we never use and, because it's annoying having this annotations, we might decide to get rid of them in the future.

Some changes were made to improve consistency, for example, the g++ compiler found a couple of instances of the code below (which is accepted by a C compiler):

enum Values {
    V1, V2, V3,
};
int main() {
    enum Values v = V1 | V2 | V3;
}

As the result of the expression is not a variant of the Values enum, it seems to me it doesn't make sense to store it in a variable of type enum Values.

Checklist

• Runs make check successfully.
• Retains 100% code coverage (make check-coverage).
• New/changed keys in YAML format are documented.
• (Optional) Adds example YAML for new feature.
• (Optional) Closes an open bug in Launchpad.

[slyon]

Thank you, those are some very good catches.
It is tedious work to fix all those paper cuts, kudos for doing it and increasing the compiler warning level, to avoid such issues going forward!

lgtm.