linux 调试工具 —— Valgrind 使用初探

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   Valgrind 是在linux系统下开发应用程序时用于调试内存问题的工具。它尤其擅长发现内存管理的问题，它可以检查程序运行时的内存泄漏问题。
   它的官方网址是
http://www.valgrind.org/
   下载最新版本的Valgrind，目前是3.2.0。 wget
http://www.valgrind.org/downloads/valkyrie-1.2.0.tar.bz2
   执行常规的安装步骤：./confgure && make && make install。注意： 系统必须安装QT的开发包。即便这样在make 时还是出现qplatformdefs.h这个文件找不到的情况，导致make失败。查找系统中的qplatformdefs.h 之后，发现没有存在于qt的标准头文件目录/usr/lib/qt-3.3/include。如是将/usr/lib/qt-3.3/mkspecs/linux-g++/ 目录下该头文件复制标准头文件目录，重新make ，后面一切OK。
初次使用    编译如下代码:  gcc -Wall example.c -g -o example
#include
void f(void)
{
   int* x = malloc(10 * sizeof(int));
   x[10] = 0;        // problem 1: heap block overrun
}                    // problem 2: memory leak -- x not freed
int main(void)
{
     f();
     return 0;
}
     注意：gcc 的-g 选项让Valgrind调试输出时指出相应信息的代码所在的行号。

valgrind --tool=memcheck --leak-check=yes ./example
==6742== Memcheck, a memory error detector for x86-linux.
==6742== Copyright (C) 2002-2004, and GNU GPL'd, by Julian Seward et al.
==6742== Using valgrind-2.2.0, a program supervision framework for x86-linux.
==6742== Copyright (C) 2000-2004, and GNU GPL'd, by Julian Seward et al.
==6742== For more details, rerun with: -v
==6742==
==6742== Invalid write of size 4
==6742==    at 0x8048384: f (example.c:6)
==6742==    by 0x80483AC: main (example.c:12)
==6742==  Address 0x1B908050 is 0 bytes after a block of size 40 alloc'd
==6742==    at 0x1B904984: malloc (vg_replace_malloc.c:131)
==6742==    by 0x8048377: f (example.c:5)
==6742==    by 0x80483AC: main (example.c:12)
==6742==
==6742== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 12 from 1)
==6742== malloc/free: in use at exit: 40 bytes in 1 blocks.
==6742== malloc/free: 1 allocs, 0 frees, 40 bytes allocated.
==6742== For counts of detected errors, rerun with: -v
==6742== searching for pointers to 1 not-freed blocks.
==6742== checked 1360800 bytes.
==6742==
==6742==
==6742== 40 bytes in 1 blocks are definitely lost in loss record 1 of 1
==6742==    at 0x1B904984: malloc (vg_replace_malloc.c:131)
==6742==    by 0x8048377: f (example.c:5)
==6742==    by 0x80483AC: main (example.c:12)
==6742==
==6742== LEAK SUMMARY:
==6742==    definitely lost: 40 bytes in 1 blocks.
==6742==    possibly lost:   0 bytes in 0 blocks.
==6742==    still reachable: 0 bytes in 0 blocks.
==6742==         suppressed: 0 bytes in 0 blocks.
==6742== Reachable blocks (those to which a pointer was found) are not shown.
==6742== To see them, rerun with: --show-reachable=yes
   上面的C程序存在两个错误：1. 数组下标越界；2. 分配的内存没有释放，存在内存泄露的问题。对于错误1，看Valgrind的调试信息片断
==6742== Invalid write of size 4
==6742==    at 0x8048384: f (example.c:6)
==6742==    by 0x80483AC: main (example.c:12)
==6742==  Address 0x1B908050 is 0 bytes after a block of size 40 alloc'd
==6742==    at 0x1B904984: malloc (vg_replace_malloc.c:131)
==6742==    by 0x8048377: f (example.c:5)
对于错误2，看这个
==6742== malloc/free: 1 allocs, 0 frees, 40 bytes allocated.
......
==6742== 40 bytes in 1 blocks are definitely lost in loss record 1 of 1
==6742==    at 0x1B904984: malloc (vg_replace_malloc.c:131)
==6742==    by 0x8048377: f (example.c:5)
==6742==    by 0x80483AC: main (example.c:12)


相关链接：
   
http://www.valgrind.org/docs/manual/quick-start.html
   
http://www-128.ibm.com/developerworks/cn/linux/l-pow-debug/



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