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

From: Jonathan Nieder <jrnieder@gmail.com>
Date: Oct 12, 2018, 18:54 UTC
Message-ID: <20181012185450.GB52080@aiede.svl.corp.google.com>
In-Reply-To: <20181012184549.GC4917@sigill.intra.peff.net>

Jeff King wrote:

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

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>> 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.

[...]

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> -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?

Thomas, do you use autoconf to generate config.mak.autogen? I'm wondering if that produces a CFLAGS 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.

Do you mean putting -Wall instead of -Wformat?

Should we add -Wextra too?  From a quick test, it seems to build okay.

Thanks, Jonathan