Using GDB under Emacs

The GNU debugger, GDB, is an interactive source-level debugger for C and several other languages. It can be run under Emacs, which provides a few rather nifty additional features. Full on-line documentation of gdb is available using the C-h i command in Emacs. The command M-x gdb will prompt for an executable file name, and then run GDB on that file, displaying the interaction in a buffer that acts much like a shell buffer described previously. Within that buffer, however, several commands have a slightly different meaning. In addition, whenever GDB displays the current position in the program (for example, after a step, at a breakpoint, or after an interrupt), Emacs will try to display the indicated source file and line in another window, with an arrow (`=>') pointing at the corresponding line in the source text (this arrow is not actually in the file being displayed).

The following commands are peculiar to GDB buffers.

C-c C-n

performs a GDB `next' command (step to next line in the source program).

C-c C-s

performs a GDB `step' command (step to next line in the source program to be executed, stopping at the beginning of any procedure that gets called.)

C-c C-i

performs a GDB `stepi' command (step to next machine-language instruction--not usually used unless you are programming in assembly language.

C-c <

performs a GDB `up' command (go up to procedure that called current one).

C-c >

performs a GDB `down' command (opposite of `up').

C-c C-r

performs a GDB `finish' command (continues from last breakpoint).

C-c C-b

set a breakpoint at the current position in the program (as indicated by the position of the `=>' arrow).

C-c C-d

delete a breakpoint (if any) at the current position in the program (as indicated by the position of the `=>' arrow).

In addition, within any source file buffer, there is the following command.

C-x SPC

puts a break point at the point in the program indicated by the cursor.