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GDB Cheat Sheet

GNU Debugger (GDB) Cheat Sheet

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# GDB Cheat Sheet
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## GDB 
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* GNU Project Debugger
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## Startup
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* % gdb -help                   print startup help, show switches
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* % gdb object                  normal debug
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* % gdb objct core              core debug (must specify core file)
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* % gdb ogject pid              attatch to running process
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* % gdb                         use file command to load object
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## Help
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* (gdb) help                    list command classes
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* (gdb) help running            list commands in one command class
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* (gdb) help run                bottom-level help for a command "run"
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* (gdb) help info               list info commands (running program state)
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* (gdb) help info line          help for a particular info command 
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* (gdb) help show               list show commands (gdb state)
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* (gdb) help show commands      specific help for a show command
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## Breakpoints
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* (gdb) break main              set a breakpoint on a function
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* (gdb) break 101               set a breakpoint on a line number
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* (gdb) break basic.c:101       set a breakpoint at file and line (or function)
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* (gdb) info breakpoints        show breakpoints
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* (gdb) delete 1                delete a breakpoint by number
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* (gdb) delete                  delete all breakpoints (prompted)
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* (gdb) clear                   delete breakpoints at currentl line
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* (gdb) clear function          delete breakpoints a function
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* (gdb) clear line              delete breakpoints at line
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* (gdb) disable 2               turn a breakpoint off, but don't remove it
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* (gdb) enable 2                turn a disabled breakpoint back on
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* (gdb) tbreak function|line    set a temporary breakpoint
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* (gdb) commands break-no ... end           set gdb commands with breakpoint
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* (gdb) ignore break-no count               ignore btp N-1 times before activation
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* (gdb) condition break-no expression       break only if condition is true
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* (gdb) condition 2 i == 20 example: break on breakpoint 2 if i equals to 20
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* (gdb) watch expression        set software watchpoint on variable
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* (gdb) info watchpoints        show current watchpoints
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## Running the Program
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* (gdb) run                     run the program with current arguments
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* (gdb) run args redirection    run with args and redirection
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* (gdb) set args args...        set arguments for run
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* (gdb) show args               show current arguments to run
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* (gdb) cont                    continue the program
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* (gdb) step                    single step the program; step into functions
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* (gdb) step count              single step \fIcount\fR times
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* (gdb) next                    step but step over functions
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* (gdb) next count              next \fIcount\fR times
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* (gdb) CTRL-C                  actually SIGINT, stop execution of current program
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* (gdb) attach process-id       attach to running program
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* (gdb) detach                  detach from running program
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* (gdb) finish                  finish current function's execution
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* (gdb) kill                    kill current executing program
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## Stack Backtrace
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* (gdb) bt                      printf stack backtrace
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* (gdb) frame                   show current execution position
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* (gdb) up                      move up stack trace (towards main)
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* (gdb) down                    move down stack trace (away from main)
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* (gdb) info locals             print automatic variable in frame
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* (gdb) info args               print function parameters
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## Browsing Source
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* (gdb) list 101                list 10 lines around line 101
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* (gdb) list 1,10               list lines 1 to 10
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* (gdb) list main               list lines around function
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* (gdb) list basic.c:main       list from another file basic.c
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* (gdb) list -                  list previous 10 lines
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* (gdb) list *0x22e4            *list source at address
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* (gdb) cd dir                  change current directory to \fIdir\fR
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* (gdb) pwd                     print working directory
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* (gdb) search regexpr          forward current for regular expression
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* (gdb) reverse-search regexpr  backward search for regular expression
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* (gdb) dir dirname             add directory to source path
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* (gdb) dir                     reset source path to nothing
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* (gdb) show directories        show source path
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## Browsing Data
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* (gdb) print expression        print expression, added to value history
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* (gdb) print/x expressionR     print in hex
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* (gdb) print array[i]@count    artificial array - print array range
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* (gdb) print $                 print last value
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* (gdb) print *$->next          *print thru list
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* (gdb) print $1                print value 1 from value history
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* (gdb) print ::gx              force scope to be global
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* (gdb) print 'basic.c'::gx     flobal scope in named file (>=4,6)
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* (gdb) print/x &main           print address of function
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* (gdb) x/countFormatSize address       low-level examine command
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* (gdb) x/x &gx                 print gx in hex
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* (gdb) x/4wx &main             print 4 longs at start of \fImain\fR in hex
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* (gdb) x/gf &gd1               print double
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* (gdb) help x                  show formats for x
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* (gdb) info locals             print local automatics only
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* (gdb) info functions regexp   print function names
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* (gdb) info variables regexp   print global variable names
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* (gdb) ptype name              print type of expression
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* (gdb) whatis expression       print type of expression
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* (gdb) set variable = expression       assign value
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* (gdb) display expression      display expression result at stop
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* (gdb) undisplay               delete displays
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* (gdb) info display            show displays
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* (gdb) show values             print value history (>= gdb 4.0)
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* (gdb) info history            print value history (gdb 3.5)
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## Object File Manipulation
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* (gdb) file object             load new file for debug (sym+exec)
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* (gdb) file                    discard sym+exec file info
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* (gdb) symbol-file object      load only symbol table
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* (gdb) exec-file object        specify object to run (not sym-file)
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* (gdb) core-file core          post-mortem debugging
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## Signal Control
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* (gdb) info signals            print signal setup
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* (gdb) handle signo actions    set debugger actions for signal
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* (gdb) handle INT print        print message when signal occurs
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* (gdb) handle INT noprint      don't print message
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* (gdb) handle INT stop         stop program when signal occurs
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* (gdb) handle INT nostop       don't stop program
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* (gdb) handle INT pass         allow program to receive signal
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* (gdb) handle INT nopass       debugger catches signal; program doesn't
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* (gdb) signal signo            continue and send signal to program
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* (gdb) signal 0                continue and send no signal to program
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## Machine-Level Debug
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* (gdb) info registers          print registers sans floats
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* (gdb) info all-registers      print all registers
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* (gdb) print/x $pc             print one register
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* (gdb) step1                   single step at machine level
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* (gdb) s1                      single step at machine level
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* (gdb) next1                   single step (over functions) at machine level
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* (gdb) n1                      single step (over functions) at machine level
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* (gdb) display/i $pc           print current instruction in display
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* (gdb) x/x &gx                 print variable gx in hex
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* (gdb) info line 22            print address for object code for line 22
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* (gdb) info line *0x2c4e       *print line number of object code at address
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* (gdb) x/10i main              disassemble first 10 instructions in \fImain\fR
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* (gdb) disassemble addr        disassemble code for function around addr
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## History Display
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* (gdb) show commands           print command history (>= gdb 4.0)
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* (gdb) info editing            print command history (gdb 3.5)
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* (gdb) EXC-CTRL-J              switch to vi edit mode from emacs edit mode
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* (gdb) set history expansion on        turn on c-shell like history
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* (gdb) break class::member     set breakpoint on class member. may get menu
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* (gdb) list class::member      list member in class
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* (gdb) ptype class             print class members
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* (gdb) print *this             *print contents of this pointer
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* (gdb) rbreak regexpr          useful for breakpoint on overloaded member name
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## Miscellaneous
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* (gdb) define command ... end  define user command
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* (gdb) RETURN                  repeat last command
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* (gdb) shell command args      execute shell command
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* (gdb) source file             load gdb commands from file
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* (gdb) quit                    quit job