Linux環境內存洩漏工具vargrind

今天又溫習了一下linux下檢測內存洩漏工具vargrind的使用：

1. 從網上看，大家都用的是valgrind工具集，valgrind包含了幾種工具：

(1) memcheck：檢查程序中的內存問題，如洩漏、越界、非法指針等。

(2) callgrind：檢測程序代碼的運行時間和調用過程，以及分析程序性能。

(3) cachegrind：分析CPU的cache命中率、丟失率，用於進行代碼優化。

(4) helgrind：用於檢查多線程程序的競態條件。

(5) massif：堆棧分析器，指示程序中使用了多少堆內存等信息。

2. 只說memcheck這個工具，它負責檢測內存問題：

(1) 使用未初始化的內存，這塊內存的值是隨機的。

(2) 使用未指向有效內存的指針，即空指針或者野指針。

(3) 內存越界方法。

(4) 內存復制區域的重疊。

使用未初始化的內存 (Use of uninitialised memory)

使用已經釋放了的內存 (Reading/writing memory after it has been free’d)

使用超過malloc分配的內存空間(Reading/writing off the end of malloc’d blocks)

對堆棧的非法訪問 (Reading/writing inappropriate areas on the stack)

申請的空間是否有釋放 (Memory leaks – where pointers to malloc’d blocks are lost forever)

malloc/free/new/delete申請和釋放內存的匹配(Mismatched use of malloc/new/new [] vs free/delete/delete [])

src和dst的重疊(Overlapping src and dst pointers in memcpy() and related functions)

重復free

3. 使用方法：

valgrind 選項--tool=name，name指定使用哪個工具，比如memcheck等。

Memcheck選項：

-leak-check=no|summary|full 要求對leak給出詳細信息，即內存洩漏的詳細信息。

4. 例子說明1：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main()
{
    char *p;
    *p = 'a';

    return 0;
}

使用分配內存且未初始化的指針p，檢測如下：

[ljq@ycy valgrind]$ valgrind --tool=memcheck ./mem-leak

==1841== Memcheck, a memory error detector

==1841== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.

==1841== Using Valgrind-3.11.0 and LibVEX; rerun with -h for copyright info

==1841== Command: ./mem-leak

==1841==

==1841== Use of uninitialised value of size 4

==1841== at 0x8048404: main (mem-leak.c:8)

==1841==

==1841==

==1841== HEAP SUMMARY:

==1841== in use at exit: 0 bytes in 0 blocks

==1841== total heap usage: 0 allocs, 0 frees, 0 bytes allocated

==1841==

==1841== All heap blocks were freed -- no leaks are possible

==1841==

==1841== For counts of detected and suppressed errors, rerun with: -v

==1841== Use --track-origins=yes to see where uninitialised values come from

==1841== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)

以上是valgrind命令檢測結果的輸出，

==1841== Use of uninitialised value of size 4 指出使用未初始化的值

==1841== at 0x8048404: main (mem-leak.c:8) 指出代碼位置行數

例子說明2：分配內存，不進行釋放。

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main()
{
    char *p = malloc(sizeof(char) * 100);

    return 0;
}

[ljq@ycy valgrind]$ valgrind --tool=memcheck --leak-check=full ./mem-leak2

==1901== Memcheck, a memory error detector

==1901== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.

==1901== Using Valgrind-3.11.0 and LibVEX; rerun with -h for copyright info

==1901== Command: ./mem-leak2

==1901==

==1901==

==1901== HEAP SUMMARY: 堆的統計信息：

==1901== in use at exit: 100 bytes in 1 blocks

==1901== total heap usage: 1 allocs, 0 frees, 100 bytes allocated 堆heap上分配了一次內存，100字節

==1901==

==1901== 100 bytes in 1 blocks are definitely lost in loss record 1 of 1 指出100字節丟失即沒有釋放

==1901== at 0x402A2C2: malloc (vg_replace_malloc.c:299)

==1901== by 0x8048445: main (mem-leak2.c:7) mem-leak2.c的第7行發生內存洩漏

==1901==

==1901== LEAK SUMMARY: leak-check選項的統計信息：

==1901== definitely lost: 100 bytes in 1 blocks 100字節絕對丟失

==1901== indirectly lost: 0 bytes in 0 blocks

==1901== possibly lost: 0 bytes in 0 blocks

==1901== still reachable: 0 bytes in 0 blocks

==1901== suppressed: 0 bytes in 0 blocks

==1901==

==1901== For counts of detected and suppressed errors, rerun with: -v

==1901== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)

以後工作中慢慢用吧。