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

[Nico Weber]

>From my understanding, /Zc: are sema-level flags. /GF- maps to
-fwritable-strings and seems to be the codegen-level flag.

On Sun, Dec 21, 2014 at 6:07 PM, David Majnemer <david.majnemer at gmail.com>
wrote:

> 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> 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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>>> >>>
>>> >
>>> >
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>>>
>>
>>
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