making valgrind able to read user input when c++ needs it -

i trying run c++ program valgrind, have points in program require user input stdin, when run valgrind, wont let user input program, there way around this?

been searching around have not found answer.

i haven't tried it, found in man pages:

--input-fd=<number> [default: 0, stdin]               specify file descriptor use reading  input                 user.    used whenever valgrind needs prompt user               decision. 

what happens if specify different fd (say, 3) valgrind use input?