/* u_1_23.c:    Undefined behaviors on generating invalid pp-token by #

        operator.   */

#include    <stdio.h>

#define str( a)     # a

main( void)

{

/*  "\\"\"";    This sequence is parsed to three tokens "\\" \ "", and will be

        diagnosed by compiler-proper unless diagnosed by preprocessor.  */

    puts( str( \""));

    return  0;

}