강의10

Size: px

Start display at page:

Download "강의10"

다현 강
5 years ago
Views:

1 Computer Programming gdb and awk 12 th Lecture 김현철컴퓨터공학부서울대학교

2 순서 C Compiler and Linker 보충 Static vs Shared Libraries ( 계속 ) gdb awk Q&A

3 Shared vs Static Libraries ( 계속 ) Advantage of Using Libraries Reduced Complexity of Managing Projects Advantages of Using Shared Libraries Reduced Size of Each Executable File Easy Library-Functions Replacement Disadvantage of Using Shared Libraries Dynamic Linking Overhead

4 gdb 기본 Features Run a Program Stop Execution within the Program Examine and Change Variables during Execution Trace How the Program Executes Provide Command-Line Editing and History Features

5 Using gdb Compilation with the g Option Generate an Expanded Symbol Table for Use with gdb martini:~$ gcc g main.c func.o Execution of gdb Permit Debugging a Program Compiled with the g Option Permit Discovering Where and Why the Program Failed (with a Core Dump) martini:~$ gdb a.out martini:~$ gdb a.out core Core dump: copy of memory image; run ulimit c unlimited to make the size unlimited

6 gdb Basic Commands help: Print a List of Commands or Topics run: Execute the Program quit: Exit gdb (gdb) help List of classes of commands (omitted) running -- Running the program (gdb) help running run -- Start debugged program Argument list (gdb) run 1 (gdb) quit [Ctrl]-C to stop the program

7 gdb Example /* test.c */ struct { int *i_p; } s; void foo() { *(s.i_p) = 2; printf("s.i = %d\n", *(s.i_p)); } main(int argc, char *argv[]){ int *i_p; *i_p = atoi(argv[1]); printf("i = %d\n", *i_p); foo(); } martini:~$ gcc g test.c martini:~$ a.out 1 i = 1 세그멘테이션오류 (core dumped)

8 gdb Example ( 계속 ) list: Show the Lines Surrounding the Code Just Executed whatis: Print the Type of a Variable or Function ptype: Show the Contents of a Data Type martini:~$ gdb a.out core (omitted) Program terminated with signal 11, Segmentation fault. #0 0x b in foo () at test.c:6 6 *(s.i_p) = 2; (gdb) list 6 *(s.i_p) = 2; (gdb) whatis s type = struct {...} (gdb) ptype s type = struct { int *i_p; } Line number more powerful than whatis Call stack number 0: most recent

9 gdb Example ( 계속 ) print: Print the Value of a Variable or Expression up/down: Move Up/Down the Stack Frame to Make another Function the Current One (gdb) print s print func() possible $1 = {i_p = 0x0} (gdb) print s.i_p Value history identifiers $2 = (int *) 0x0 The error occurred at *(s.i_p) = 2; (gdb) print *(s.i_p) Cannot access memory at address 0x0 (gdb) up #1 0x080484c9 in main (argc=2, argv=0xbffffce4) at test.c:15 15 foo(); (gdb) print i_p $3 = (int *) 0xbffffc98 (gdb) print *i_p $4 = 1 (gdb) print $4+1 $5 = 2

10 gdb Example ( 계속 ) backtrace/where: Print the Current Location and a Stack Trace set variable: Assign a Value to a Variable print: Print the Assigned Value martini:~$ gdb a.out (omitted) (gdb) run 1 Program received signal SIGSEGV, Segmentation fault. 0x b in foo () at test.c:6 6 *(s.i_p) = 2; (gdb) backtrace #0 0x b in foo () at test.c:6 #1 0x080484c9 in main (argc=2, argv=0xbffffcb4) at test.c:15 (gdb) up #1 0x080484c9 in main (argc=2, argv=0xbffffcb4) at test.c:15 15 foo(); (gdb) set variable (*i_p)++ (gdb) print *i_p += 1 $1 = 3 same as where Assignments do not work with core

11 gdb Example ( 계속 ) break: Set Breakpoints in the Program watch: Set Break-If Breakpoints info breakpoints: Show All Breakpoints and Watchpoints martini:~$ gdb a.out (omitted) (gdb) break foo Breakpoint 1 at 0x : file test.c, line 6. (gdb) break test.c:6 Note: breakpoint 1 also set at pc 0x Breakpoint 2 at 0x : file test.c, line 6. (gdb) run 1 Breakpoint 1, foo () at test.c:6 6 *(s.i_p) = 2; (gdb) watch *i_p > 0 Hardware watchpoint 3: *i_p > 0 (gdb) info breakpoints (omitted) 5 void foo() { 6 *(s.i_p) = 2;

12 gdb Example ( 계속 ) kill: Abort the Running Process delete: Delete a Breakpoint or a Watchpoint next: Execute the Next Line, Executing a Function (gdb) kill Kill the program being debugged? (y or n) y (gdb) delete 2 9 (omitted) (gdb) delete 1 10 main() (gdb) break Int *i_p; Breakpoint 4 at 0x : file test.c, line (gdb) run 1 Breakpoint 1, main (argc=2, argv=0xbffffcb4) at test.c:12 12 *i_p = atoi(argv[1]); (gdb) print *i_p $1 = (gdb) next 13 printf("i = %d\n", *i_p); (gdb) print *i_p $2 = 1

13 gdb Example ( 계속 ) step: Execute the Next Line, Stepping into a Function continue: Continue Execution (gdb) kill Kill the program being debugged? (y or n) y (gdb) run 1 (omitted) (gdb) step 13 printf("i = %d\n", *i_p); (gdb) step i = 1 15 foo(); (gdb) step foo () at test.c:6 6 *(s.i_p) = 2; (gdb) continue

14 gdb Example ( 계속 ) info line: Show Where the Object Code Begins and Ends disassemble: Produce a Machine Listing info registers: List Integer Registers and Their Contents (gdb) kill Kill the program being debugged? (y or n) y (gdb) run 1 (omitted) (gdb) info line 12 Line 12 of "test.c" starts at address 0x <main+9> and ends at 0x80484af <main+35>. (gdb) disassemble main (gdb) x 0x80484ca 0x80484ca <main+62>: ret 0x80484ca <main+62>: 0x895590c3 (gdb) info registers

15 awk (Aho Weinberger Kernighan) PL for Computing and Data-Manipulation Tasks (Especially, Columns of Data) Example EXECUTION TIME = 2.0 EXECUTION TIME = 4.2 martini:~$ awk {sum = sum + $4} END {print "avg = " sum/nr} temp martini:~$ awk f avg.awk temp

Microsoft PowerPoint - System Programming Lab Week1.ppt [호환 모드]

Microsoft PowerPoint - System Programming Lab Week1.ppt [호환 모드] System Programming Lab Week 1: Basic Skills for Practice Contents vi Editor 사용법 GCC 컴파일러사용법 Makefile 사용법 GDB 사용법 VI Editor Usage vi 모드 입력모드 : 실제문서를편집하는모드. 명령모드 : 키입력이바로명령이되는모드로서쓴내용을삭제하거나, 복사할때사용. ex 명령모드