Using stringize and string concatenation in ghc preprocessing

[Boespflug, Mathieu]

Hi Harendra,

I ran into this very problem recently. Turns out -traditional knows string
concatenation too. I seem to remember learning this by browsing the GHC
source code, but now I can't find any occurrence of this pattern. But
here's an example of how to do string concatenation with CPP in
-traditional mode:
https://github.com/tweag/sparkle/blob/a4e481aa5180b6ec93c219f827aefe932b66a953/inline-java/src/Foreign/JNI.hs#L274
.

HTH,

--
Mathieu Boespflug
Founder at http://tweag.io.

On 20 August 2016 at 20:33, Brandon Allbery <allbery.b at gmail.com> wrote:

> On Sat, Aug 20, 2016 at 2:27 PM, Harendra Kumar <harendra.kumar at gmail.com>
> wrote:
>
>> But "-optP" seems to only append to the flags that GHC already passes and
>> gcc has no "-no-traditional" option to undo the effect of the
>> "-traditional" that GHC has already passed. I think "-optP" should override
>> the flags passed by ghc rather than appending to them. Is there a reason
>> not to do that?
>>
>> Is there any other better way to achieve this? What is the standard way
>> of doing this if any?
>>
>
> Removing -traditional will break much Haskell source. Go look at the
> history of clang with ghc (clang doesn't do -traditional) to see what
> happens. (tl;dr: without -traditional, cpp knows too much about what
> constitutes valid C, and mangles and/or throws errors on valid Haskell that
> doesn't lex the way C does.)
>
> You might want to look at cpphs as an alternative preprocessor. There are
> some ancient K&R-era hacks that could be used if absolutely necessary, but
> cpphs should be a much simpler and cleaner solution.
>
> --
> brandon s allbery kf8nh                               sine nomine
> associates
> allbery.b at gmail.com
> ballbery at sinenomine.net
> unix, openafs, kerberos, infrastructure, xmonad
> http://sinenomine.net
>
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