[patch, clang-cl] Implement /Zc:trigraphs support, disable trigraphs by default

[Nico Weber]

On Mon, Dec 22, 2014 at 1:38 AM, Hans Wennborg <hans at chromium.org> wrote:

> On Sun, Dec 21, 2014 at 5:24 PM, Nico Weber <thakis at chromium.org> wrote:
> > That's much nicer, thanks. I couldn't figure out how to alias a clang-cl
> > option to a cc1 option, so I added 4 lines to explicitly translate
> > OPT__SLASH_Zc_trigraphs to -ftrigraphs, but it's still much simpler.
>
> Hmm, that's a little annoying, but I guess it makes sense.. the
> clang-cl flags are handled as Driver flags so aliasing to a CC1
> doesn't work.
>
> Perhaps we should just stick to the existing -trigraphs and add a
> -no-trigraphs driver flag? lgtm either way I guess.
>

Richard, are you okay with adding a -no-trigraphs gcc-driver-level flag?
gcc doesn't have this, but several people on the internet are asking for
this feature (I searched for `gcc "no-trigraphs"`). I'd like a way to build
with -std=c++11 (i.e. not gnu++11) but still not enable trigraphs myself,
too.


>
> > I also used the same technique to map /Zc:strictStrings to
> > -Werror=c++11-compat-deprecated-writable-strings while here.
>
> Nice.
>
> > (Disabling trigraphs in -fms-compatibility mode for the gcc driver makes
> > sense to me too, but I think that should happen in a different patch.)
>
> > Property changes on: test/Driver/cl-zc.cpp
> > ___________________________________________________________________
> > Added: svn:eol-style
> > ## -0,0 +1 ##
> > +LF
>
> Is this intentional?
>
>
> > On Sun, Dec 21, 2014 at 4:36 AM, Hans Wennborg <hans at chromium.org>
> wrote:
> >>
> >> I would have broken out /Zc:trigraphs[-] into two separate CLFlag
> >> options instead.
> >>
> >> That way we don't need parser code for it, the flags can have
> >> individual help texts, and they can just be aliases to the cc1 flags.
> >>
> >> Also, instead of passing -fno-trigraphs each time, maybe we should
> >> change the default in CompilerInvocation based on the language
> >> options. It seems we currently disable them in gnu mode for example.
> >> Maybe we should do the same if -fms-extensions or -fms-compatibility
> >> if enabled?
> >>
> >> On Sat, Dec 20, 2014 at 11:16 AM, Nico Weber <thakis at chromium.org>
> wrote:
> >> > Thanks! All done.
> >> >
> >> > On Fri, Dec 19, 2014 at 6:47 PM, Richard Smith <richard at metafoo.co.uk
> >
> >> > wrote:
> >> >>
> >> >> On Fri, Dec 19, 2014 at 6:08 PM, Nico Weber <thakis at chromium.org>
> >> >> wrote:
> >> >>>
> >> >>> Forgot to say: Fixes PR21974.
> >> >>>
> >> >>> On Fri, Dec 19, 2014 at 6:07 PM, Nico Weber <thakis at chromium.org>
> >> >>> wrote:
> >> >>>>
> >> >>>> Hi,
> >> >>>>
> >> >>>> the attached patch disables trigraphs by default in clang-cl mode.
> To
> >> >>>> do
> >> >>>> so, I'm renaming the cc1 trigraph flag to -ftrigraphs, and I'm
> adding
> >> >>>> a
> >> >>>> -fno-trigraphs flag. (This requires updating a handful of cc1
> tests,
> >> >>>> and
> >> >>>> translating -trigraphs to -ftrigraphs in the driver.)
> >> >>>>
> >> >>>> The driver grows parsing logic for /Zc:, everything other than
> >> >>>> trigraphs
> >> >>>> is ignored for now. (We probably want to implement at least
> >> >>>> /Zc:inline at
> >> >>>> some point, which is why I added parsing code for this instead of
> >> >>>> always
> >> >>>> sending -fno-trigraphs to cc1 in clang-cl mode.)
> >> >>
> >> >>
> >> >> -def trigraphs : Flag<["-", "--"], "trigraphs">, Flags<[CC1Option]>,
> >> >> +def trigraphs : Flag<["-", "--"], "trigraphs">,
> Flags<[DriverOption]>,
> >> >>
> >> >> I don't think DriverOption is right here; that means we don't forward
> >> >> the
> >> >> flag to a gcc invocation. Now, we never invoke GCC for C-like
> languages
> >> >> any
> >> >> more, but if we did, this would be wrong (and for all I know, it's
> >> >> wrong for
> >> >> Fortran...). You should be able to just drop the Flags.
> >> >>
> >> >>
> >> >>      if (Arg *A = Args.getLastArg(options::OPT_std_EQ,
> >> >> options::OPT_ansi,
> >> >> -                                 options::OPT_trigraphs))
> >> >> -      if (A != Std)
> >> >> +                                 options::OPT_trigraphs)) {
> >> >> +      if (A->getOption().matches(options::OPT_trigraphs))
> >> >> +        CmdArgs.push_back("-ftrigraphs");
> >> >> +      else if (A != Std)
> >> >>          A->render(Args, CmdArgs);
> >> >>
> >> >> Std here is Args.getLastArg(options::OPT_std_EQ, options::OPT_ansi),
> so
> >> >> your 'else if' clause is unreachable. Something like this would be
> >> >> simpler
> >> >> and more obvious:
> >> >>
> >> >> // If -trigraphs appears after the language standard flag, honor it.
> >> >> if (Args.getLastArg(options::OPT_std_EQ, options::OPT_ansi,
> >> >> options::OPT_trigraphs) != Std)
> >> >>   CmdArgs.push_back("-ftrigraphs");
> >> >>
> >> >> You could even sink this below the 'if (Std)' block to avoid
> >> >> duplicating
> >> >> it between the cases where we do and don't have a Std flag.
> >> >>
> >> >>>> Ok?
> >> >>>>
> >> >>>> Nico
> >> >>>
> >> >>>
> >> >>>
> >> >>> _______________________________________________
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> >> >>> cfe-commits at cs.uiuc.edu
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> >> >>>
> >> >
> >> >
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> >> >
> >
> >
>
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