Re: [PATCH 1/2] introduce "banned function" list

[Jeff King <peff@peff.net>]

On Fri, Jul 20, 2018 at 04:41:34PM +0200, Duy Nguyen wrote:

> > Let's start by banning strcpy() and sprintf(). It's not
> > impossible to use these correctly, but it's easy to do so
> > incorrectly, and there's always a better option.
> 
> Is it possible to extend this to ban variables as well? I'm still
> going to delete the_index from library code. Once that work is done I
> will ban it from entering again (it's only allowed in builtin/ for
> example). The next target after that would be the_repository.
> 
> Right now I will do this by not declaring the variable [2], which ends
> up with a much less friendly compile warning. I did something similar
> [1] in an earlier iteration but did not do extensive research on this
> topic like you did.

IMHO just not declaring the variable is the right move (and is what I
would do with these functions if libc wasn't already declaring them).

The compile error may be less friendly, but these things are temporary
as topics-in-flight catch up. Whereas strcpy() will be with us forever.

I also think that removing variables is a special case of a larger
technique: when we change function semantics, we try to change the
signatures, too. So there you'll get a type error, or not enough
arguments, or whatever. And the next step is usually "git log" or "git
blame" to see what happened, and what the conversion should look like.

-Peff