Re: RFC: should we use -Werror? (& sample patch to do it)

[Zack Weinberg <zack at codesourcery dot com>]

On Tue, Sep 04, 2001 at 11:32:50PM -0400, Kaveh R. Ghazi wrote:
> I got warning levels down to around 30 on solaris2.7 and 20 on irix6.
> So I thought it might be worth a try to get -Werror installed in gcc.
...
> Anyway, another problem is we have to get to zero warnings before
> using -Werror.  I propose doing it one module at a time.  The patch
> below is a candidate which does this for rtl.o to start with.  If that
> lasts for a week without major pandemonium, we can do more files.

I think this is backward.  First we should get to zero warnings
throughout the compiler, _then_ we talk about -Werror.  If only
because if we do it your way, we'll be adding explicit compile rules
to module after module.  I don't think there's enough marginal benefit
from -Werror applied to a few modules, to eat that kind of complexity
burden in the Makefile which is already too complicated.

Instead, we should be talking seriously about the remaining N
warnings, and what we're going to do about them.  I saw a couple of
patches go by for the 20-odd signed/unsigned comparison warnings in
combine.c, which is the majority of the remaining warnings; they
haven't been reviewed.

Next biggest offender is

       7 string length `???' is greater than the length `???' ISO C89
         compilers are required to support

These are more or less intractable: they come from big hairy spec
strings, e.g.

    "%{E|M|MM:cpp0 -lang-c++ %{!no-gcc:-D__GNUG__=%v1}\
       %{!Wno-deprecated:-D__DEPRECATED}\
       %{!fno-exceptions:-D__EXCEPTIONS}\
       -D__GXX_ABI_VERSION=100\
       %{ansi:-D__STRICT_ANSI__ -trigraphs -$} %(cpp_options)}\
     %{!E:%{!M:%{!MM:\
       %{save-temps:cpp0 -lang-c++ \
                    %{!no-gcc:-D__GNUG__=%v1}\
                    %{!Wno-deprecated:-D__DEPRECATED}\
                    %{!fno-exceptions:-D__EXCEPTIONS}\
                    -D__GXX_ABI_VERSION=100\
                    %{ansi:-D__STRICT_ANSI__ -trigraphs -$}\
                    %(cpp_options) %b.ii \n}\
      cc1plus %{save-temps:-fpreprocessed %b.ii}\
              %{!save-temps:%(cpp_options)\
                            %{!no-gcc:-D__GNUG__=%v1} \
                            %{!Wno-deprecated:-D__DEPRECATED}\
                            %{!fno-exceptions:-D__EXCEPTIONS}\
                            -D__GXX_ABI_VERSION=100\
                            %{ansi:-D__STRICT_ANSI__}}\
       %{ansi:-trigraphs -$}\
       %(cc1_options) %2 %{+e1*}\
       %{!fsyntax-only:%(invoke_as)}}}}",

Anyone have a good suggestion for what to do about that, I would
*love* to hear it.  (Short of Neil's driver rewrite, which isn't
happening fast enough to help.)

zw