emacs and gdb-many-windows

i am new to emacs. In many site there is a opition to set gdb-many-windows which actually split the window like

 |   GUD buffer (I/O of GDB)      |   Locals/Registers buffer      |

 |   Primary Source buffer        |   I/O buffer for debugged pgm  |

 |   Stack buffer                 |   Breakpoints/Threads buffer   |

Whenever i try to do "M-x gdb-many-window" it does not recognize it. "M-x gdb" et开发者_如何学Python al works well but not "M-x gdb-many-window"?

Does anyone have faced this one?

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Read this and this. M-x gdb-many-windows works after M-x gdb and the gud window is in focus. Your question suggests that you are trying for M-x gdb-many-windows before M-x gdb.