Re: [PATCH] config.mak.dev: add -Wformat

From: Jeff King <peff@peff.net>
Date: Oct 12, 2018, 18:45 UTC
Message-ID: <20181012184549.GC4917@sigill.intra.peff.net>
In-Reply-To: <20181012184037.15076-1-t.gummerer@gmail.com>

On Fri, Oct 12, 2018 at 07:40:37PM +0100, Thomas Gummerer wrote:

Show 15 quoted lines

> 801fa63a90 ("config.mak.dev: add -Wformat-security", 2018-09-08) added
> the -Wformat-security to the flags set in config.mak.dev.  In the gcc
> man page this is documented as:
> 
>          If -Wformat is specified, also warn about uses of format
>          functions that represent possible security problems.  [...]
> 
> That commit did however not add the -Wformat flag, and -Wformat is not
> specified anywhere else by default, so the added -Wformat-security had
> no effect.  Newer versions of gcc (gcc 8.2.1 in this particular case)
> warn about this and thus compilation fails with this option set.
> 
> Fix that, and make -Wformat-security actually useful by adding the
> -Wformat flag as well.  git compiles cleanly with both these flags
> applied.

-Wformat is part of -Wall, which we already turn on by default (even for non-developer builds).

So I don't think we need to do anything more, though I'm puzzled that you saw a failure. Do you set CFLAGS explicitly in your config.mak to something that doesn't include -Wall?

I'm not opposed to making config.mak.dev a bit more redundant to handle this case, but we'd probably want to include all of -Wall, since it contains many other warnings we'd want to make sure are enabled.

-Peff