Fix a compilation warning in command.c relating to kpos shadowing

[natoscott]

When building with the gcc -Wshadow option, a warning is generated in redis_parse_cmd() because the second and third declarations of the same-named kpos variable share scope. It's benign but it'd be great to have clean compilation when using this option.

[zuiderkwast]

Thanks.

Shadowing can cause bugs because you can mix up the two variables, but reusing the same variable multiple times in a larger scope can cause a similar mix up too. There's no warning for the latter though.

I see that each time the kpos variable is used, it is only the following lines, so the real scope is actually just these lines:

    kpos = hiarray_push(r->keys);
    if (kpos == NULL)
        goto oom;
    kpos->start = arg;
    kpos->end = arg + arglen;

We have a change here to avoid shadowing and also get rid of some duplicated code. We can wrap those lines in a function, like

static inline int push_keypos(struct cmd *r, char *arg, uint32_t arglen) {
    struct keypos *kpos = hiarray_push(r->keys);
    if (kpos == NULL)
        return 0;
    kpos->start = arg;
    kpos->end = arg + arglen;
    return 1;
}

and call it like

    if (!push_keypos(r, arg, arglen))
        goto oom;

WDYT?

[natoscott]

@zuiderkwast that's an excellent idea IMO.

[bjosv]

LGTM!