in emacs, it returns an error "internal error", 

and emacs's cpu usage becomes full forever, except for restarting emacs,

It seems emacs might process something wrong in this case.

The issue can be easily reproduced by directly eval following sexp:

(call-process-region (point-min) (point-max)
                     "cmdproxy.exe"
                     t
                     t
                     nil
                     "-c"
                     "gitk")