[cfe-dev] Language not recognized: 'c++-module-cpp-output'

[David Blaikie via cfe-dev]

On Sat, Jun 3, 2017 at 6:54 AM Boris Kolpackov <boris at codesynthesis.com>
wrote:

> David Blaikie <dblaikie at gmail.com> writes:
>
> > Does this actually speed up clang in an observable way?
>
> I haven't measured, but I very much doubt there will be any significant
> speedup if you are going all the way to the object code, so to speak.
> The benefit will come if you want to send the file for compilation on
> a remote host. In this case you won't need to start the compiler locally
> at all.
>

Not sure I follow this - that's a benefit to the build system in knowing
whether it needs to preprocess the file before sending it to the remote
system. But not a benefit to the compiler/clang.


>
>
> > What makes it more likely for modularized code? In the sense that many
> more
> > source files won't /need/ to use the preprocessor, so they're sort of
> > quasi-preprocessed (trivially, in the sense that there's no work to do)
> > already?
>
> Yes, exactly. They won't need #include's and quite a bit of code could
> probably be written without relying on macros (especially so for module
> interface units).
>
> One hold out is assert(). Maybe it can be done as a compiler intrinsic?
>

I don't think it can, but maybe - the issue being that the contents of the
assert expression mustn't be evaluated or even parsed, etc, if assertions
are not enabled.


>
> Boris
>
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