Breakpoint와 Watchpoint 분석 — Conditional·Hardware·Catchpoint

1
(gdb) break 42 if x > 100
2
(gdb) b factorial if n == 0
3
(gdb) b parser.c:50 if strcmp(buf, "ERROR") == 0

1
for (int i = 0; i < 10000; i++) {
2
    if (data[i].value == 0) {
3
        process(data[i]);  // ← 특정 i에서만 멈추고 싶음
4
    }
5
}

1
(gdb) b 4 if i == 5234 && data[i].value == 0

1
b 42 if x > 100 && y < 0          # 논리 연산
2
b 42 if my_func(x) != 0           # 함수 호출 (side effect 주의)
3
b 42 if strcmp(s, "key") == 0     # 문자열
4
b 42 if ((Node*)p)->next == NULL  # 캐스팅
5
b 42 if i == count - 1            # 산술

1
(gdb) break 42
2
Breakpoint 1 at ...
3

4
(gdb) commands 1
5
> print x
6
> print y
7
> continue
8
> end

1
(gdb) commands 1
2
> silent
3
> printf "Loop %d: x=%d y=%d\n", i, x, y
4
> continue
5
> end

1
Loop 1: x=10 y=20
2
Loop 2: x=15 y=18
3
Loop 3: x=22 y=15
4
...

1
(gdb) break 42
2
(gdb) ignore 1 1000      # 1번 breakpoint를 1000번 무시

1
(gdb) tbreak main       # 한 번 멈추면 자동 삭제
2
(gdb) tb main           # 약어

1
(lldb) breakpoint set --one-shot --name main
2
(lldb) b -o main

1
(gdb) rbreak handle_.*
2
Breakpoint 1 at ...: file foo.c, line 10.
3
Breakpoint 2 at ...: file foo.c, line 25.
4
...

1
(gdb) watch x          # x가 변경될 때 멈춤
2
(gdb) watch -location my_struct.field   # 주소 기준

1
int balance = 100;
2

3
void process() {
4
    // ... 어딘가에서 balance가 -1이 됨, 어디서?
5
}

1
(gdb) watch balance
2
(gdb) run
3
...
4
Hardware watchpoint 2: balance
5
Old value = 100
6
New value = 50
7
process_withdrawal (amount=50) at account.c:42
8
42      balance -= amount;
9

10
(gdb) continue
11
Hardware watchpoint 2: balance
12
Old value = 50
13
New value = -1
14
bug_function () at bug.c:18
15
18      balance = -1;       # ← 여기 범인!

1
(gdb) watch x          # 쓰기에만 (변경)
2
(gdb) rwatch x         # 읽기에만
3
(gdb) awatch x         # 읽기 + 쓰기 (access)

1
(gdb) watch x
2
Hardware watchpoint 1: x        # 빠름!

1
(gdb) watch (long array)[100]   # 큰 영역
2
Hardware watchpoint 2: ...
3
warning: Could not insert hardware watchpoint 2.

1
(gdb) set can-use-hw-watchpoints 0   # software 강제
2
(gdb) watch big_array
3
Watchpoint 3: big_array

1
void inner() {
2
    int local = 0;
3
    // 여기에 watch
4
}
5

6
void outer() {
7
    inner();
8
    // inner 종료 후 local은 사라짐
9
}

1
Watchpoint 1 deleted because the program has left the block in
2
which its expression is valid.

1
(gdb) catch throw       # 모든 C++ 예외 throw
2
(gdb) catch catch       # 모든 catch
3
(gdb) catch signal SIGSEGV    # SIGSEGV 발생 시
4
(gdb) catch syscall open      # open() 시스템 콜
5
(gdb) catch fork              # fork()
6
(gdb) catch exec              # exec()
7
(gdb) catch load              # 동적 라이브러리 로드

1
(gdb) catch throw
2
Catchpoint 1 (throw)
3

4
(gdb) run
5
Catchpoint 1 (exception thrown), 0x... in __cxa_throw () from libstdc++
6

7
(gdb) bt
8
#0  __cxa_throw
9
#1  parse_data () at parser.c:25
10
#2  main () at main.c:10

1
(gdb) catch throw std::runtime_error    # 특정 예외만

1
(lldb) breakpoint set --name __cxa_throw
2
(lldb) breakpoint set -E c++

1
(gdb) catch syscall open
2
Catchpoint 1 (syscall 'open' [2])
3

4
(gdb) run
5
Catchpoint 1 (call to syscall open), 0x... in open ()

1
(gdb) disable 1         # 1번 비활성 (안 삭제)
2
(gdb) enable 1          # 다시 활성
3
(gdb) disable 1-5       # 1~5 일괄
4
(gdb) enable count 5 2  # 2번을 5번 카운트 후 자동 비활성
5
(gdb) enable delete 3   # 3번이 한 번 트리거되면 삭제

1
(gdb) hbreak main       # hardware breakpoint

1
(gdb) break parse_data
2
(gdb) commands
3
> silent
4
> printf "parse_data called with input='%s'\n", input
5
> continue
6
> end

1
(gdb) break 50 if error_count > 0
2
(gdb) commands
3
> print error_message
4
> info locals
5
> bt 5
6
> continue
7
> end

1
(gdb) break race_condition_func
2
(gdb) commands
3
> set var shared_state = 0    # 강제 초기화
4
> continue
5
> end

1
(gdb) info signals
2
Signal       Stop  Print Pass  Description
3
SIGHUP       Yes   Yes   Yes   Hangup
4
SIGINT       Yes   Yes   No    Interrupt
5
SIGSEGV      Yes   Yes   Yes   Segmentation fault
6
SIGPIPE      No    Yes   Yes   Broken pipe
7
...

1
(gdb) handle SIGPIPE nostop noprint
2
(gdb) handle SIGSEGV stop print pass

1
// 아직 로드 안 된 라이브러리의 함수에 break
2
break my_plugin_function
3
Function "my_plugin_function" not defined.
4
Make breakpoint pending on future shared library load? (y or [n]) y
5
Breakpoint 1 (my_plugin_function) pending.

1
(gdb) set breakpoint pending on    # 자동으로 pending 만들기

1
(gdb) print my_struct.value
2
$1 = 42
3

4
(gdb) watch my_struct.value
5
(gdb) continue
6
Hardware watchpoint 2: my_struct.value
7
Old value = 42
8
New value = -1
9
buggy_function () at bug.c:88

1
(gdb) b process_record if record_id == 12345
2
(gdb) commands
3
> bt 5
4
> info locals
5
> continue
6
> end
7
(gdb) run

1
(gdb) catch throw std::out_of_range
2
(gdb) run
3

4
Catchpoint 1 (exception thrown), ...
5
(gdb) bt