cpp/io/cerr

The global objects and  control output to a stream buffer of implementation-defined type (derived from std and std, respectively), associated with the standard C error output stream stderr.

These objects are guaranteed to be initialized during or before the first time an object of type std is constructed and are available for use in the constructors and destructors of static objects with ordered initialization (as long as is included before the object is defined).

Unless has been issued, it is safe to concurrently access these objects from multiple threads for both formatted and unformatted output.

Once initialized, (same for ) meaning that any output sent to these stream objects is immediately flushed to the OS (via std's destructor).

In addition, returns  (same for  and std), meaning that any output operation on  first executes  (via std's constructor).