Implicit function declarations and GCC 10

[Segher Boessenkool]

On Fri, Jul 05, 2019 at 09:15:12AM +0200, Florian Weimer wrote:
> * Segher Boessenkool:
> 
> > Hi Florian,
> >
> > On Fri, Jul 05, 2019 at 07:49:21AM +0200, Florian Weimer wrote:
> >> > We already have an option for that (-Werror=implicit-function-declaration),
> >> > and it is an error by default with -pedantic-errors already.  If you are
> >> > asking to make it an error by default, I second that; there needs to be a
> >> > wat to turn it off though.  Maybe it should be an error for c99 and later
> >> > only, anyway?
> >> 
> >> Yes, it should be an error by default, without any flags.  Which is
> >> gnu11 mode by now, I think.  So it's not sufficient to do this for
> >> c99/c11 mode.
> >
> > When I say "c99 and later", of course that includes gnu99 and gnu11.  My
> > point is that we probably shouldn't by default error on this in c90 mode,
> > since it is a valid construct there, and not extraordinarily harmful.
> 
> Ah, sorry.  Yes, this isn't for c90 mode.  I'm less concerned with
> programmers who set -std=, they can use
> -Werror=implicit-function-declaration as well if they want.  It is
> really the flag-less default that matters to me.

Yup.

> What I meant is that this works just fine on 32-bit architectures
> because there is no truncation involved.

You mean "it most likely does what the author intended".  Ah.

> >> >> Implicit int we should remove as well.  Checking configure scripts for
> >> >> both issues at the same time would not be much more work.
> >> >
> >> > We could enable -Wimplicit-int by default for c99 and later, maybe even
> >> > its -Werror- version.  This conflicts with at least -fms-extensions it,
> >> > seems, dunno what to do there.
> >> 
> >> We can keep this a separate discussion if it helps.
> >
> > Yes please.  Can you make separate PRs?  There is essentially no
> > overlap.
> 
> I filed PR91092 and PR91093.

Thanks!


Segher