breakpoint can not set within emacs

[John Smith <horserivers at gmail dot com>]

hi,
 I  start gdb within emacs , emacs  show me  the start  src file
which  is main.cpp, then I  step into functions  ,and  it comes into
other  directory and file , when I  type "break"
command,gdb prompt  this breakpoint is at main.cpp, it seem to be
emacs  can not  auto change  to  files  which  the debug process  is
at

so   Is  there some  advice?


thanks!