The purpose of this ladebug session is to show how to start using ladebug. It covers the how to use the following ladebug commands:
If you know gdb already, you will find using ladebug is almost the same as using gdb for those basic commands. For this example the source code is example.c and the input for the process is ex_input.
The first step in debugging is to compile the source with the debugging option. This is the -g option.
$ gcc -g example.c -o example example.c: In function `add_list': example.c:61: warning: assignment makes pointer from integer without a cast $
After the source is compiled, you can run the executable in ladebug.
Before you start the debugger, make sure that you have correctly set the size information for your terminal; otherwise, the debugger's command line editing support may act unpredictably. For example, if your terminal is 47x80, you may need to set the following:
% stty rows 47 ; setenv LINES 47 % stty cols 80 ; setenv COLS 80 $ ladebug ./example Welcome to the Ladebug Debugger Version 4.0-43 ------------------ object file name: ./example Reading symbolic information ...done (ladebug)
To begin to walk through the code set a breakpoint at the function main before you run the process so that you can stop the process and see which lines get executed.
(ladebug) stop in main [#1: stop in int main(int, char**) ] (ladebug)
Run the process.
(ladebug) run ex_input
[1] stopped at [main:135 0x120001c20]
135 if (argc != 2)
(ladebug)To run the process one line of code type next.
(ladebug) next
stopped at [main:141 0x120001c84]
141 fp = fopen(argv[1], "r");
(ladebug)In ladebug you can repeat the previous command by typing a carriage return.
(ladebug) next
stopped at [main:142 0x120001cb0]
142 if (fp == NULL)
(ladebug)
(ladebug) next
stopped at [main:148 0x120001ce8]
148 init_queue(&q);
(ladebug) next
stopped at [main:150 0x120001cf4]
150 fgets(line, sizeof(line), fp);
stopped at [main:151 0x120001d14]
151 while (!(feof(fp)))
stopped at [main:156 0x120001d34]
156 if (line[0] == '?')
stopped at [main:159 0x120001d44]
159 int num = count_queue(&q);
stopped at [main:160 0x120001d58]
160 printf("queue is %d long\n",num);
queue is 0 long
stopped at [main:161 0x120001d78]
161 print_list(&q);
stopped at [main:164 0x120001d84]
164 } else if (line[0] == 'a')
stopped at [main:178 0x120001e24]
178 fgets(line, sizeof(line), fp);
stopped at [main:179 0x120001e44]
179 }
stopped at [main:151 0x120001d14]
151 while (!(feof(fp)))
stopped at [main:156 0x120001d34]
156 if (line[0] == '?') As you can see, next steps through the code a line at a time. Notice that next does not enter functions.
If you want to step through code and enter functions use the step command.
(ladebug) step
stopped at [main:167 0x120001d98]
167 if (1 == sscanf(&line[1],"%d",&data))
stopped at [main:168 0x120001dd0]
168 add_queue(&q, data);
stopped at [add_queue:109 0x120001a94]
109 assert(q != NULL);
(ladebug)
step has entered the add_queue function.
(ladebug) step
stopped at [add_queue:111 0x120001ad0]
111 return add_list(q,data);
stopped at [add_list:58 0x1200017c4]
58 assert(head != NULL);
stopped at [add_list:59 0x120001800]
59 ptr = *head;
stopped at [add_list:61 0x12000180c]
61 newptr = malloc(sizeof(LL));
stopped at [add_list:62 0x120001828]
62 if (newptr == NULL) {
stopped at [add_list:66 0x120001854]
66 newptr->data = data;
To examine data you can use the print command.
(ladebug) print newptr
0x140000940
(ladebug) print *newptr
struct linked_list {
data = 0;
next = 0x0;
}
(ladebug) print data
123
(ladebug) To kill the debug session use the kill command.
(ladebug) kill Process has exited (ladebug)
To exit ladebug use the quit command.
(ladebug) quit
$
Summary of commands
command abbr description
format
-------- ----- ------------
run [args] r start program with args
next [count] n step count lines of code
step [count] s step count lines of code
including function calls
stop in addr bp set breakpoint at addr
stop at [line] b set breakpoint at line number
print value p print the value
kill k kill the process being debugged
quit q quit ladebug
name definition usage
----- ----------- ------
args command line arguments -i
as if run from a shell < input > output
count a number, default is 1 10
addr function main
line line number "example.c":100
0x120001c20
value variable, expression loszFileName
&pch1
*poiVal[i]
The debugger has the following predefined aliases:
(ladebug)
F1 print
F2 print 'F2 executes the command "F2 selected-text" - define alias F2'
F3 print 'F3 executes the command "F3 selected-text" - define alias F3'
S next
Si nexti
W list $curline - 10:20
a assign
att attach
b stop at
bp stop in
c cont
d delete
det detach
e file
exit quit
f func
focus ladebug multi select
g goto
h history
j status
l list
li ($cursrcpc)/10 i; set $cursrcpc = $cursrcpc + 40
n next
ni nexti
p print
pb printb
pd printd
pi printi
plist show process all
po printo
pr printregs
ps printf "%s",
pt printt
px printx
q quit
r rerun
ri record input
ro record output
s step
si stepi
source playback input
sw switch
switch process
t where
tlist show thread
ts where thread all
tset thread
tstack where thread all
u list $curline - 9:10
w list $curline - 5:10
wi ($curpc - 20)/10 i
wm watch memory
wv watch variable