void ct_report_error( const char * msg );
The default reporting function writes the input character string to standard error, followed by a newline. In some environments, such as a graphical user interface, this default treatment is not appropriate. By using ct_install_error_reporter() the application can replace the default reporting function with a customized callback function.
The Cheap Threads software uses ct_report_error() to report internal error conditions. Hence an application may need to install a reporting function even if it never calls ct_report_error() on its own.