2.5. Adding Commands to GDB

As noted in Section 2.2, GDB's command handling is extensible. Commands are grouped into a number of command lists (of type struct cmd_list_element), pointed to by a number of global variables (defined in cli-cmds.h). Of these, cmdlist is the list of all defined commands, with separate lists defined for sub-commands of various top level commands. For example infolist is the list of all info sub-commands.

Each command (or sub-command) is associated with a callback function which implements the behavior of the functions. There are additional requirements for functions which set or show values within GDB. Each function also takes a documentation string (used by the help command). Functions for adding commands all return a pointer to the struct cmd_list_element for the command added (which is not necessarily the head of its command list). The most useful functions are:

add_cmd. Add a function to a command list.
add_com. Add a function to the main command list, cmdlist. This is a convenience wrapper for add_cmd.
add_prefix_cmd. Add a new prefix command. This command should have its own function for use if it is called on its own, and a global command list pointer specific to the prefix command to which all its sub-commands will be added. If a prefix command is called with an unknown sub-command, it can either give an error or call the function of the prefix command itself. Which of these is used is specified by a flag in the call to add_prefix_cmd.
add_alias_cmd. Add an alias for a command already defined.
add_info. Add a sub-command to the info. A convenience wrapper for add_cmd.

New commands are usually added in the _initialize_arch function after the struct gdbarch has been defined.