Re: [PATCH] Show dangerous warning when -Werror option is used

[David Malcolm <dmalcolm at redhat dot com>]

On Sun, 2018-04-01 at 22:40 +0200, Pali Rohár wrote:
> On Sunday 01 April 2018 14:32:26 Segher Boessenkool wrote:
> > On Sun, Apr 01, 2018 at 12:05:40PM +0200, Pali Rohár wrote:
> > > Command line option -Werror is dangerous as it could cause
> > > problems for
> > > compiling applications in future. Once gcc introduces a new
> > > warning or
> > > change logic for existing warnings then compilation of existing
> > > application via gcc could throw a new warning.
> > > 
> > > As -Werror makes all warnings fatal, it makes applications not
> > > compilable. -Werror makes sense only for specific gcc versions
> > > against
> > > which was application tested to compile correctly.
> > > 
> > > Attached patch adds a new warning when -Werror command line
> > > option is
> > > enabled. It warns user that usage of -Werror can be dangerous.
> > 
> > While I love this patch in principle...
> > 
> > All patches need to be bootstrapped and regression tested.  Did
> > you?
> 
> Yes! Tested and it successfully failed on libgomp bootstrap part.
> 
>   cc1: error: command line option ‘-Werror’ is dangerous; in future
> newly introduced non-fatal warnings can cause fatal errors [-Werror]
>   cc1: all warnings being treated as errors

The patch sets:
  dc->warning_as_error_requested = value;
before issuing the warning_at, and hence the warning is itself affected
and treated as an error, making -Werror unusable, and thus forcing
people to turn it off.

I'm working on the assumption, based on today's date [1], that this is
the intended behavior of the patch?  My apologies if I'm
misunderstanding.

Dave

> > On what target?
> 
> x86_64-linux-gnu
> 
> > And I think a feature as big as this one isn't suitable for stage
> > 4.
> > 
> > 
> > Segher
> 
> 
[1] it's been almost 12 hours