gets with C++ and GCC before 4.7

[Roland McGrath]

> As I said in the gcc bug, gcc should define a macro if the declaration
> is needed and this macro should be defined only when absolutely
> necessary.

No solution in that direction works without modifying GCC releases that
have already been made.  Getting 4.7 and later to define a macro that says
the declaration can safely be omitted seems like a better bet.

Your general point applies to basically any use of __GNUC_PREREQ.
In practice, people using modified GCC versions with backports have
indeed changed glibc headers to match in their modified glibc versions.