[Bug c++/70587] 0e1_p+0 should not be parsed as a single pp-number in C++14 and earlier

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70587

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
It's rejected in -std=gnu++11 and gnu++14 mode, but not -std=c++11 / c++14,
which agrees with the documentation for -std:

> when a GNU dialect of a standard is specified, all features supported by the compiler are enabled, even when those features change the meaning of the base standard.  As a result, some strict-conforming programs may be rejected.

Hex literals have been supported as a GNU extension for many years, that's one
of the reasons they are being standardized for C++17.