[Bug libstdc++/82346] [5.5 Regression] String is not detected as a part of std

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82346

--- Comment #9 from Jonathan Wakely <redi at gcc dot gnu.org> ---
In gcc-6 and later the condition is different:

#if __cplusplus >= 201103L
...
#if _GLIBCXX_USE_C99_STDIO

So the <math.h> changes in glibc won't affect std::to_string() (but you will be
missing functionality in <cmath> instead).

This is a bug in a package you got from Ubuntu, please talk to your vendor.