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

> Jonathan Nieder <jrnieder@gmail.com> writes:
> 
> > In October, Thomas Gummerer wrote:
> >> On 10/12, Jonathan Nieder wrote:
> >>> Jeff King wrote:
> >>> ...
> >>>> -Wformat is part of -Wall, which we already turn on by default (even for
> >>>> non-developer builds).
> > ...
> > As discussed in [1], autoconf appears to not put -Wall in CFLAGS:
> >
> >  $ make configure
> >      GEN configure
> >  $ ./configure
> > [...]
> >  config.status: creating config.mak.autogen
> >  config.status: executing config.mak.autogen commands
> >  $ grep CFLAGS config.mak.autogen
> >  CFLAGS = -g -O2
> >  PTHREAD_CFLAGS=-pthread
> >
> > So this trap for the unwary is still around.
> >
> > Can we revive this patch?  Does it just need a clearer commit message,
> > or were there other objections?
> 
> I think it is a good idea to give fallback/redundancy for this
> case.  I do not have strong opinion between -Wall and -Wformat,
> but I'd probably vote for the former if pressed.

> -- >8 --
> From: Thomas Gummerer <t.gummerer@gmail.com>
> Date: Fri, 12 Oct 2018 19:40:37 +0100
> Subject: [PATCH] config.mak.dev: add -Wformat
> 
> 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.  [...]
> 
> The commit did however not add the "-Wformat" flag, but instead
> relied on the fact that "-Wall" is set in the Makefile by default
> and that "-Wformat" is part of "-Wall".
> 
> Unfortunately, those who use config.mak.autogen generated with the
> autoconf to configure toolchain do *not* get "-Wall" in their CFLAGS
> and the added -Wformat-security had no effect.  Worse yet, newer
> versions of gcc (gcc 8.2.1 in this particular case) warn about the
> lack of "-Wformat" and thus compilation fails only with this option
> set.
> 
> We could fix it by adding "-Wformat", but in general we do want all
> checks included in "-Wall", so let's add it to config.mak.dev to
> cover more cases.
> 
> Signed-off-by: Thomas Gummerer <t.gummerer@gmail.com>
> Helped-by: Jeff King <peff@peff.net>
> Helped-by: Jonathan Nieder <jrnieder@gmail.com>
> [jc: s/-Wformat/-Wall/]
> Signed-off-by: Junio C Hamano <gitster@pobox.com>
> ---
>  config.mak.dev | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/config.mak.dev b/config.mak.dev
> index bfbd3df4e8..74337f1f92 100644
> --- a/config.mak.dev
> +++ b/config.mak.dev
> @@ -1,6 +1,7 @@
>  ifeq ($(filter no-error,$(DEVOPTS)),)
>  CFLAGS += -Werror
>  endif
> +CFLAGS += -Wall
>  CFLAGS += -Wdeclaration-after-statement
>  CFLAGS += -Wformat-security
>  CFLAGS += -Wno-format-zero-length
> -- 
> 2.20.1-2-gb21ebb671b
>