Q) 그냥 프로그램이 실행되고 끝나요!

A) run 명령어를 입력하기 전에, 살펴보고자 하는 함수의 이름이나 위치에 브레이크포인트를 걸어보세요.

(lldb) b get_next_line
Breakpoint 1: where = app.out`get_next_line, address = 0x0000000100003610`
(lldb) run
Process 12345 launched: '<your/program/path>' (x86_64)
Process 12345 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = breakpoint 1.1
    frame #0: 0x000000010000251b app.out`get_next_line(fd=4) at get_next_line.c:103:9
   100 		char				*line;
   101 		char				*temp;
   102
-> 103 		if (fd < 0 || BUFFER_SIZE < 1)
   104 			return (NULL);
   105 		node = gnl_lstset(&head, fd);
   106 		if (node == NULL)
Target 0: (app.out) stopped.

Q) 디버깅이 레지스터 명령어 단위로 실행돼요!

A) 컴파일을 할 때, 디버깅 옵션(-g)를 붙여주세요.

# gcc main.c
> lldb a.out

...
Process 12345 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = breakpoint 1.1
    frame #0: 0x0000000100003610 app.out`get_next_line
app.out`get_next_line:
->  0x100003610 <+0>: pushq  %rbp
    0x100003611 <+1>: movq   %rsp, %rbp
    0x100003614 <+4>: subq   $0x30, %rsp
    0x100003618 <+8>: movl   %edi, -0xc(%rbp)
Target 0: (app.out) stopped.

# gcc -g main.c
> lldb a.out

...
Process 12345 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = breakpoint 1.1
    frame #0: 0x000000010000251b app.out`get_next_line(fd=4) at get_next_line.c:103:9
   100 		char				*line;
   101 		char				*temp;
   102
-> 103 		if (fd < 0 || BUFFER_SIZE < 1)
   104 			return (NULL);
   105 		node = gnl_lstset(&head, fd);
   106 		if (node == NULL)
Target 0: (app.out) stopped.

Q) 매번 명령어를 실행할 때마다 fr v 를 입력하는게 너무 귀찮아요!

A) lldb 명령창에 target stop-hook add --one-liner "frame variable" 를 입력해보세요.

(lldb) target stop-hook add --one-liner "frame variable"
Stop hook #1 added.
(lldb) n
(int) fd = 4
(t_list *) node = 0x00000003040c74e0
(char *) line = 0x0000003000000008 ""
(char *) temp = 0x00000001089f0719 ""
Process 73998 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = step over
    frame #0: 0x0000000100002539 app.out`get_next_line(fd=4) at get_next_line.c:105:27
   102
   103 		if (fd < 0 || BUFFER_SIZE < 1)
   104 			return (NULL);
-> 105 		node = gnl_lstset(&head, fd);
   106 		if (node == NULL)
   107 			return ((char *)gnl_lstclear(&head, fd));
   108 		temp = node->backup;

Q) v 명령어를 입력해도 전역변수가 안보여요!

A) ta v (target variable) 명령어를 입력해보세요.

(lldb) ta v
Global variables for <your/program/function> in <your/program/path>:
(t_list *) head = 0x0000603000001a80

Q) 반복문에 빠져버렸어요!

A) 무한루프 바깥의 행 번호에 브레이크포인트를 걸고 c (continue) 명령어를 입력해보세요.

Process 73998 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = step over
    frame #0: 0x0000000100002b20 app.out`gnl_strjoin(s1="Ut", s2=" enim ad minim veniam, quis nostrud exerci") at get_next_line_utils.c:52:2
   49  		while (s1[len1] != '\\0')
   50  			len1++;
   51  		len2 = 0;
-> 52  		while (s2[len2] != '\\0')  # 빠져나올 수 없는 반복문의 늪...
   53  			len2++;
   54  		string = malloc(sizeof(char) * (len1 + len2) + 1);
   55  		if (string == NULL)
Target 0: (app.out) stopped.
# 아무리 n을 눌러도 while문을 빠져나올 수 없어...!!