Re: [PATCH] Documentation: warn against using int, hex, string options as expressions in Kconfig

Nathan Chancellor <[email protected]> Thu, 30 Jul 2026 17:25:34 -0700
Newsgroups org.kernel.vger.linux-kbuild,org.kernel.vger.linux-doc,org.kernel.vger.linux-kernel
Message-ID <178545753473.3004192.2499981065379649802.b4-review@b4>
> I've been working on type checking Kconfig, and found some instances of
> dead code due to conditions that always evaluate to false.
> 
> For example:
> 
> config FOO
>   int
> 
> config BAR
>   bool
>   default 'y' if FOO

Drop this quoting of y for clarity?

> This 'if FOO' will always be false, regardless of FOO's value (even when
> FOO=1). The same goes for strings and hex.

Hmmm, it might be kind of nice to either:

1. Warn about this in Kconfig directly (if possible)
2. Support this usage in Kconfig how one would intuitively expect from
   either C or Python where symbols with values of 0, 0x0, and '' would
   be treated as false and every other value set as true.

> See also this related patch:
> https://lore.kernel.org/all/[email protected]/
> 
> Let's warn users against this usage.

That said, until either of those potentially happen, this patch seems
fine.

Reviewed-by: Nathan Chancellor <[email protected]>

-- 
Cheers,
Nathan