[PATCH] libcpp: Fix up ##__VA_OPT__ handling [PR89971]

[Jeff Law]

On 12/30/2021 2:24 AM, Jakub Jelinek via Gcc-patches wrote:
> Hi!
>
> In the following testcase we incorrectly error about pasting / token
> with padding token (which is a result of __VA_OPT__); instead we should
> like e.g. for ##arg where arg is empty macro argument clear PASTE_LEFT
> flag of the previous token if __VA_OPT__ doesn't add any real tokens
> (which can happen either because the macro doesn't have any tokens
> passed to ... (i.e. __VA_ARGS__ expands to empty) or when __VA_OPT__
> doesn't have any tokens in between ()s).
>
> Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok
> for trunk?
>
> 2021-12-30  Jakub Jelinek  <jakub@redhat.com>
>
> 	PR preprocessor/89971
> libcpp/
> 	* macro.c (replace_args): For ##__VA_OPT__, if __VA_OPT__ expands
> 	to no tokens at all, drop PASTE_LEFT flag from the previous token.
> gcc/testsuite/
> 	* c-c++-common/cpp/va-opt-9.c: New test.
OK
jeff