[PATCH] update -Wall and -Wextra documentation

[Bernd Schmidt]

On 12/10/2015 12:07 AM, Martin Sebor wrote:
>
> 	* invoke.texi (Warning Options): Update -Wall options.  Clarify
> 	when some -Wextra options are enabled.  Add -Wplacement-new example.

I tried to check this list against c.opt - I figure this should contain 
essentially the ones that are have an EnabledBy(Wall), plus whatever 
logic there is in c-opts.

> +-Wduplicated-cond  @gol

I don't see this one as enabled by Wall, and

2015-10-02  Marek Polacek  <polacek@redhat.com>

	* c.opt (Wduplicated-cond): Don't enable by -Wall anymore.

> +-Wplacement-new @r{(only for C++)} @gol

This one appears to be on by default?

> +In C++, this warning is also enabled by @option{-Wall}.  In C, it is also
> +enabled by @option{-Wextra}; to get the other warnings of @option{-Wextra}
> +without this warning, use @option{-Wextra -Wno-sign-compare}.

Is the last part of the sentence really necessary? It kind of follows 
from the rest of the documentation and we don't spell this out for other 
-Wextra options.


Bernd