Format letters for p and p commands.
- M-x gdb
- invoke gdb from emacs
- interrupt, return control to gdb
- quit gdb
- start program from beginning
- cancel the running program
- continue execution (from breakpoint, etc.)
- finish this function and break on return
- ret value
- return immediately from this function with value
- continue and break at next statement
- continue and break at next statement in this function
- break function
- set breakpoint at entry to function function
- clear function
- clear any breakpoint set at entry to function function
- M-x gdb-break
- set breakpoint at source line containing emacs cursor
- info break
- display list of breakpoints
- delete bnum
- clear breakpoint specified by bnum
- frame 0
- display source, etc., for innermost stack frame
- frame n
- for n>0, display source, etc., for caller of frame n-1
- display backtrace of function calls.
- p exp
- evaluate exp in the context of current frame and print
its value in the format implied by its type.
- p/letter exp
- evaluate exp in context of current frame and print
its value in the format specified by letter.
- x/letter exp
- similar to p, but exp is treated as an address and
the memory contents at that address are displayed.
- a address
- c character
- d signed decimal
- f floating point
- i instruction (assembler syntax)
- o octal
- s string
- u unsigned decimal
- x hexadecimal
To change the value of a program (or convenience) variable,
use and assignment as exp in a p command; e.g.,
p x=1 sets the variable x to 1.
- most recent value printed
- next to most recent value printed
- nth value printed
- $r0, $r1, ..., $r15
- registers r0, r1, ..., r15
- $pc, $ap, ...
- registers pc, ap, ...
- process status longword
To debug a function, try setting a breakpoint at the function,
and using p commands to call the function, e.g.,
p f(5,s) calls f with arguments 5 and s
and, if a breakpoint has been set, breaks immediately on entering the function.
You can then step through the function, examine variables,
It is often useful to set a breakpoint at main before running
After giving an x command, subsequent returns (i.e.,
the RETURN key) are intepreted as x commands with the
same format and applied to the memory address following the one just
Sun May 29 16:30:03 EDT 1994