[Bug libstdc++/70276] Writing to standard output concurrently through `std::cout` triggers a datarace

[stefan at vectorfabrics dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70276

--- Comment #1 from Stefan Holdermans <stefan at vectorfabrics dot com> ---
A possible solution would be to make the accesses to `std::ios_base::_M_width`
from `std::ios_base::width()` and `std::ios_base::width(streamsize)` atomic.

Currently, these functions are defined by

  streamsize
  width() const
  { return _M_width; }

and

  streamsize
  width(streamsize __wide)
  {
    streamsize __old = _M_width;
    _M_width = __wide;
    return __old;
  }

respectively.