[Patch] libcpp: Fix _Pragma in #__VA_ARGS__ [PR103165]

[Joseph Myers]

On Thu, 18 Nov 2021, Jakub Jelinek via Gcc-patches wrote:

> Are we handling the pragma at a wrong phase of preprocessing?

I think that converting it to a single preprocessing token (rather than 
four separate preprocessing tokens), at a stage when stringizing might 
still occur, does indicate it's being processed too soon, and it would be 
better to do that only when it's known that the _Pragma preprocessing 
token will actually occur in the results of preprocessing the source file.

-- 
Joseph S. Myers
joseph@codesourcery.com