Sample C++ code, let's call it test.cpp.
#include <iostream>
#include <string>
typedef struct goo {
int gooInt;
std::string gooString;
}GOO;
int main(void)
{
GOO myGOO;
myGOO.gooInt = 42;
myGOO.gooString = "answer";
int myVar = 5;
for (int i = 0; i < 10; i++)
myVar += i;
return(0);
}
Use -g flag to enable extra debugging information.
oz@LynxGwyn:~/sample_lldb$ clang++ -g test.cpp -o test
Attach the debugger.
oz@LynxGwyn:~/sample_lldb$ lldb test
Set a breakpoint to the main()
(lldb) b main
Breakpoint 1: where = test main + 19 at test.cpp:12, address = 0x0000000000400a53
you can use this syntax to set a breakpoint to other functions as well. (e.g lldb b foo )
Start the process
(lldb) run
Process 7254 stopped
* thread #1: tid = 7254, 0x0000000000400a53 test main + 19 at test.cpp:11, name = 'test', stop reason = breakpoint 1.1
frame #0: 0x0000000000400a53 test main + 19 at test.cpp:11
8
9 int main(void)
10 {
-> 11 GOO myGOO;
12 myGOO.gooInt = 42;
13 myGOO.gooString = "answer";
14
To set a breakpoint on individual lines.
(lldb) b *lineno* or (lldb) b *filename.cpp:lineno*
(lldb) b 16 or (lldb) b test.cpp:16
Breakpoint 2: where = main + 63 at test.cpp:16, address = 0x0000000000400a7f
To list the currently set breakpoints
(lldb) breakpoint list
Current breakpoints:
1: name = 'main', locations = 1, resolved = 1, hit count = 1
1.1: where = test main + 19 at test.cpp:11, address = 0x0000000000400a53, resolved, hit count = 1
2: file = '/home/oz/gl/test.cpp', line = 16, exact_match = 0, locations = 1, resolved = 1, hit count = 1
2.1: where = test main + 63 at test.cpp:16, address = 0x0000000000400a7f, resolved, hit count = 1
Use (lldb) c twice to continue until second break point
To get the current local variable values
(lldb) frame variable or simply (lldb) fr var
(GOO) myGOO = (gooInt = 42, gooString = "answer")
(int) myVar = 5
(int) i = 0
To get an individual variable's value
(lldb) frame var myGOO
(GOO) myGOO = (gooInt = 42, gooString = "answer")
You can use watchpoints to stop the execution when a value changes
(lldb) watch set var myVar
watchpoint created: Watchpoint 1: addr = 0x7fffffffdd70 size = 4 state = enabled type = w
declare @ '/home/oz/gl/test.cpp:15'
watchpoint spec = 'myVar'
new value: 5
To set a stopping condition
(lldb) watch modify -c '(myVar>9)'
Use (lldb) c to continue until the myVar reaches above 9
Process 7430 resuming
Watchpoint 1 hit:
old value: 5
new value: 11
Process 7430 stopped
* thread #1: tid = 7430, 0x0000000000400a99 test main + 89 at test.cpp:16, name = 'test', stop reason = watchpoint 1
frame #0: 0x0000000000400a99 test main + 89 at test.cpp:16
13 myGOO.gooString = "answer";
14
15 int myVar = 5;
-> 16 for (int i = 0; i < 10; i++)
17 myVar += i;
18
19 return(0);
Use (lldb) watchpoint list or (lldb) watch l to get the currently set watchpoints
Current watchpoints:
Watchpoint 1: addr = 0x7fffffffdd70 size = 4 state = enabled type = w
declare @ '/home/oz/gl/test.cpp:15'[I'm an inline-style link](https://www.google.com)
watchpoint spec = 'myVar'
old value: 5
new value: 11
condition = '(myVar>9)'
Use (lldb) watch del 1 to delete the watchpoint
1 watchpoints deleted.
Use (lldb) c to finish execution!
Process 7576 exited with status = 0 (0x00000000)
Congrats!
Additional Sources: