Valgrind로 메모리 누수 체크하기!!

복잡한 프로그램을 개발하다보면,, 메모리 관리가 제대로 안될 때가 많다.
원래 malloc()해주고 free() 꼭 넣어주는게 정석이것만.. 진짜진짜 이게 잘 안된다..ㅋㅋ
그래서 프로그램이 죽기도 하고, 메모리 사용량이 계속 늘어나기도 하고, 프로그램을 죽였는데도
메모리 사용량이 줄어들지 않을 때도 있다.

입사하고서 그런 버그를 잡을 수 있는 획기적인 툴을 발견했다.
바로바로 Valgrind!!
지금까지 꾸준히 사용하고 있는 완소 툴이다 ♡

리눅스에서 valgrind -h 또는 valgrind --help  쳐보면, 다음과 같은 설명이 나온다.
사용법은 간단함.

>valgrind -h usage: valgrind [options] prog-and-args  common user options for all Valgrind tools, with defaults in [ ]:     --tool=<name>             use the Valgrind tool named <name> [memcheck]     -h --help                 show this message     --help-debug              show this message, plus debugging options     --version                 show version     -q --quiet                run silently; only print error msgs     -v --verbose              be more verbose, incl counts of errors     --trace-children=no|yes   Valgrind-ise child processes? [no]     --track-fds=no|yes        track open file descriptors? [no]     --time-stamp=no|yes       add timestamps to log messages? [no]     --log-fd=<number>         log messages to file descriptor [2=stderr]     --log-file=<file>         log messages to <file>.<pid>     --log-file-exactly=<file> log messages to <file>     --log-file-qualifier=<VAR> incorporate $VAR in logfile name [none]     --log-socket=ipaddr:port  log messages to socket ipaddr:port   uncommon user options for all Valgrind tools:     --run-libc-freeres=no|yes free up glibc memory at exit? [yes]     --sim-hints=hint1,hint2,...  known hints:                                  lax-ioctls, enable-outer [none]     --show-emwarns=no|yes     show warnings about emulation limits? [no]     --smc-check=none|stack|all  checks for self-modifying code: none,                               only for code found in stacks, or all [stack]     --kernel-variant=variant1,variant2,...  known variants: bproc [none]                               handle non-standard kernel variants  user options for Valgrind tools that report errors:     --xml=yes                 all output is in XML (some tools only)     --xml-user-comment=STR    copy STR verbatim to XML output     --demangle=no|yes         automatically demangle C++ names? [yes]     --num-callers=<number>    show <number> callers in stack traces [12]     --error-limit=no|yes      stop showing new errors if too many? [yes]     --error-exitcode=<number> exit code to return if errors found [0=disable]     --show-below-main=no|yes  continue stack traces below main() [no]     --suppressions=<filename> suppress errors described in <filename>     --gen-suppressions=no|yes|all    print suppressions for errors? [no]     --db-attach=no|yes        start debugger when errors detected? [no]     --db-command=<command>    command to start debugger [gdb -nw %f %p]     --input-fd=<number>       file descriptor for input [0=stdin]     --max-stackframe=<number> assume stack switch for SP changes larger                               than <number> bytes [2000000]  user options for Memcheck:     --leak-check=no|summary|full     search for memory leaks at exit?  [summary]     --leak-resolution=low|med|high   how much bt merging in leak check [low]     --show-reachable=no|yes          show reachable blocks in leak check? [no]     --undef-value-errors=no|yes      check for undefined value errors [yes]     --partial-loads-ok=no|yes        too hard to explain here; see manual [no]     --freelist-vol=<number>          volume of freed blocks queue [5000000]     --workaround-gcc296-bugs=no|yes  self explanatory [no]     --alignment=<number>      set minimum alignment of allocations [8] ......이하생략

 

노랑색 하이라이트된것은 내가 자주 사용하는 애들..ㅎㅎㅎ

보통 다음과 같이 사용한다.

valgrind  프로그램 --tool=memcheck --leak-check=yes --show-reachable=yes --log-file="./valgrind_log

사용 예를 한번..들어보자면 

간단한 test 프로그램 작성 (메모리 누수 발생시킴)

 

#include <stdio.h>
#include <stdlib.h>
typedef struct _test_t {
    int data;
}test_t;
int main(void)
{
    test_t *test;
    test = malloc(sizeof(test_t));
    test->data = 3;
    printf("test->data = %d\n", test->data);

    return 0;
}

한눈에 봐도 메모리 누수가 일어날 것을 알수 있다...(free안했음)

valgrind 를  실행시키면, 

 valgrind ./test --tool=memcheck --leak-check=summary
==19358== Memcheck, a memory error detector.
==19358== Copyright (C) 2002-2007, and GNU GPL'd, by Julian Seward et al.
==19358== Using LibVEX rev 1732, a library for dynamic binary translation.
==19358== Copyright (C) 2004-2007, and GNU GPL'd, by OpenWorks LLP.
==19358== Using valgrind-3.2.3, a dynamic binary instrumentation framework.
==19358== Copyright (C) 2000-2007, and GNU GPL'd, by Julian Seward et al.
==19358== For more details, rerun with: -v
==19358==
test->data = 3
==19358==
==19358== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 13 from 1)
==19358== malloc/free: in use at exit: 4 bytes in 1 blocks.
==19358== malloc/free: 1 allocs, 0 frees, 4 bytes allocated.
==19358== For counts of detected errors, rerun with: -v
==19358== searching for pointers to 1 not-freed blocks.
==19358== checked 48,380 bytes.
==19358==
==19358== LEAK SUMMARY:
==19358==    definitely lost: 4 bytes in 1 blocks.
==19358==      possibly lost: 0 bytes in 0 blocks.
==19358==    still reachable: 0 bytes in 0 blocks.
==19358==         suppressed: 0 bytes in 0 blocks.
==19358== Rerun with --leak-check=full to see details of leaked memory.

 

 라고 메모리 누수가 발생했음을 알려준다.
다시 free 루틴을 넣고 컴파일 한다음 valgrind를 돌리게 되면

 [root@lkalove]# valgrind ./test --tool=memcheck --leak-check=summary
==19427== Memcheck, a memory error detector.
==19427== Copyright (C) 2002-2007, and GNU GPL'd, by Julian Seward et al.
==19427== Using LibVEX rev 1732, a library for dynamic binary translation.

==19427== Copyright (C) 2004-2007, and GNU GPL'd, by OpenWorks LLP.
==19427== Using valgrind-3.2.3, a dynamic binary instrumentation framework.
==19427== Copyright (C) 2000-2007, and GNU GPL'd, by Julian Seward et al.
==19427== For more details, rerun with: -v
==19427==
test->data = 3
==19427==
==19427== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 13 from 1)
==19427== malloc/free: in use at exit: 0 bytes in 0 blocks.
==19427== malloc/free: 1 allocs, 1 frees, 4 bytes allocated.
==19427== For counts of detected errors, rerun with: -v
==19427== All heap blocks were freed -- no leaks are possible.

다음과 같이 모든 메모리가 정상적으로  free되었고 메모리 누수가 없음을 알려준다!!

정말 좋은 툴