An uncaught exception or a failed assert can cause your program to terminate unexpectedly, before you manage to output anything. One way to see if this is happening is to put your entire main() function in a try {} catch(...) {} block. Then - either in the body of catch(...) or at the very start of main() - you should try writing something to std::cerr (any protocol) or std::cout (CGI/aCGI only). The following is a template:

main()
try
{
  // In almost all cases std::cerr is available (check your server's error logs).
  std::cerr<< "Program started ok..." << std::endl << std::flush;

  std::cout<< "Content-type: text/plain\r\n\r\n" // the required content-type header
           << "TESTING"
           << std::flush; // make sure you flush the buffer as soon as possible!

  // ...

}catch(...){
  std::cerr<< "Caught exception in main()" << std::endl << std::flush;
  std::cout<< "Content-type: text/plain\r\n\r\n"
           << "Caught exception!" << std::flush;
}

Because this library depends on compiled libraries, you may find that your application crashes before it even starts running. If you find you can't even write to std::cerr at the very start of your program then you may have a runtime linking problem.

The easiest way around this is to statically link your program. If you're using bjam you can use the command:

bjam link=static runtime-link=static

	Tip
	To check what directories are searched for libraries, try one of the echo examples on your server and look for a variable like LIB_DIR or LIB.