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

[David Majnemer]

Should we map /Zc:strictStrings- to fwritable-strings?

On Sunday, December 21, 2014, 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.
>
> I also used the same technique to map /Zc:strictStrings
> to -Werror=c++11-compat-deprecated-writable-strings while here.
>
> (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.)
>
> On Sun, Dec 21, 2014 at 4:36 AM, Hans Wennborg <hans at chromium.org
> <javascript:_e(%7B%7D,'cvml','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
>> <javascript:_e(%7B%7D,'cvml','thakis at chromium.org');>> wrote:
>> > Thanks! All done.
>> >
>> > On Fri, Dec 19, 2014 at 6:47 PM, Richard Smith <richard at metafoo.co.uk
>> <javascript:_e(%7B%7D,'cvml','richard at metafoo.co.uk');>>
>> > wrote:
>> >>
>> >> On Fri, Dec 19, 2014 at 6:08 PM, Nico Weber <thakis at chromium.org
>> <javascript:_e(%7B%7D,'cvml','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
>> <javascript:_e(%7B%7D,'cvml','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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