如何使用Valgrind调试C++内存泄漏？

如何使用 Valgrind 调试 C++ 内存泄漏

Valgrind 是一个功能强大的内存调试器，可用于检测 C++ 程序中的内存泄漏、非法使用和分配问题。下面介绍如何使用 Valgrind 调试 C++ 内存泄漏：

1. 安装 Valgrind

使用以下命令安装 Valgrind：

sudo apt install valgrind

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2. 编译和调试

在编译程序时，添加 -g 标记以生成调试信息：

g++ -g my_program.cpp -o my_program

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然后，使用 Valgrind 运行程序，并使用 –leak-check=full 标记来检查内存泄漏：

valgrind --leak-check=full ./my_program

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3. 分析 Valgrind 输出

Valgrind 的输出将包含有关检测到的内存泄漏的信息。

实战案例

以下是一个模拟内存泄漏的简单 C++ 程序：

#include <iostream>

int* leak() {
  int* ptr = new int;
  return ptr;
}

int main() {
  int* ptr = leak();
  return 0;
}

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编译并使用 Valgrind 运行此程序：

g++ -g leak.cpp -o leak
valgrind --leak-check=full ./leak

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Valgrind 的输出将包含以下信息：

==27244== Memcheck, a memory error detector
==27244== Copyright (C) 2002-2017, and GNU GPL'd by, Julian Seward et al.
==27244== Using Valgrind-3.15.0.
==27244== Command: ./leak
==27244==
==27244== HEAP SUMMARY:
==27244==     in use at exit: 4 bytes in 1 blocks
==27244==   total heap usage: 1 allocs, 0 frees, 4 bytes allocated
==27244==
==27244== LEAK SUMMARY:
==27244==    definitely lost: 4 bytes in 1 blocks
==27244==    indirectly lost: 0 bytes in 0 blocks
==27244==      possibly lost: 0 bytes in 0 blocks
==27244==    still reachable: 0 bytes in 0 blocks
==27244==         suppressed: 0 bytes in 0 blocks
==27244== Rerun with --leak-check=full to see what's still reachable
==27244==
==27244== For counts of detected and suppressed errors, rerun with: -v
==27244== Use --track-origins=yes to see where unfreed memory was allocated
==27244== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)
==27244==
==27244== 1 errors in context 0 of 1:
==27244== Invalid read of size 8
==27244==    at 0x4842E10: leak (leak.cpp:5)
==27244==    by 0x483D8E7: main (leak.cpp:12)
==27244==  Address 0x555555555600 is not stack'd, malloc'd or (recently) free'd
==27244==
==27244== LEAK SUMMARY:
==27244==    definitely lost: 0 bytes in 0 blocks
==27244==    indirectly lost: 0 bytes in 0 blocks
==27244==      possibly lost: 4 bytes in 1 blocks
==27244==    still reachable: 0 bytes in 0 blocks
==27244==         suppressed: 0 bytes in 0 blocks
==27244== Rerun with --leak-check=full to see what's still reachable
==27244==
==27244== For counts of detected and suppressed errors, rerun with: -v
==27244== Use --track-origins=yes to see where unfreed memory was allocated

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此输出表明程序中存在 4 字节的内存泄漏，该泄漏来自函数 leak() 中未释放的 int 指针。

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