[Bug libstdc++/79789] [6/7 Regression] non-reserved names in headers

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79789

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
And this fails since 5.1.0 with C++11 or later:

#define e 1
#include <ios>

And this fails for all versions at least as far back as 4.3 (although it's only
valid in C++98 and C++03 because C++11 adds member functions called a() in
<random>):

#define a 1
#include <valarray>

There are a few other problems too.