防止内存泄露 Linux下用Valgrind做检查

下面举两个用valgrind做内存检查的例子

　　例子一 (test.c)：

　　#include <string.h>

　　int main(int argc, char *argv[])

　　{

　　char *ptr;

　　ptr = (char*) malloc(10);

　　strcpy(ptr, "01234567890");

　　return 0;

　　}

　　编译程序

　　gcc -g -o test test.c

　　用valgrind执行命令

　　valgrind --tool=memcheck --leak-check=yes ./test

　　报告如下

　　==4270== Memcheck, a memory error detector.

　　==4270== Copyright (C) 2002-2006, and GNU GPL'd, by Julian Seward et al.

　　==4270== Using LibVEX rev 1606, a library for dynamic binary translation.

　　==4270== Copyright (C) 2004-2006, and GNU GPL'd, by OpenWorks LLP.

　　==4270== Using valgrind-3.2.0, a dynamic binary instrumentation framework.

　　==4270== Copyright (C) 2000-2006, and GNU GPL'd, by Julian Seward et al.

　　==4270== For more details, rerun with: -v

　　==4270==

　　==4270== Invalid write of size 1

　　==4270== at 0x4006190: strcpy (mc_replace_strmem.c:271)

　　==4270== by 0x80483DB: main (test.c:8)

　　==4270== Address 0x4023032 is 0 bytes after a block of size 10 alloc'd

　　==4270== at 0x40044F6: malloc (vg_replace_malloc.c:149)

　　==4270== by 0x80483C5: main (test.c:7)

　　==4270==

　　==4270== Invalid write of size 1

　　==4270== at 0x400619C: strcpy (mc_replace_strmem.c:271)

　　==4270== by 0x80483DB: main (test.c:8)

　　==4270== Address 0x4023033 is 1 bytes after a block of size 10 alloc'd

　　==4270== at 0x40044F6: malloc (vg_replace_malloc.c:149)

　　==4270== by 0x80483C5: main (test.c:7)

　　==4270==

　　==4270== ERROR SUMMARY: 2 errors from 2 contexts (suppressed: 12 from 1)

　　==4270== malloc/free: in use at exit: 10 bytes in 1 blocks.

　　==4270== malloc/free: 1 allocs, 0 frees, 10 bytes allocated.

　　==4270== For counts of detected errors, rerun with: -v

　　==4270== searching for pointers to 1 not-freed blocks.

　　==4270== checked 51,496 bytes.

　　==4270==

　　==4270==

　　==4270== 10 bytes in 1 blocks are definitely lost in loss record 1 of 1

　　==4270== at 0x40044F6: malloc (vg_replace_malloc.c:149)

　　==4270== by 0x80483C5: main (test.c:7)

　　==4270==

　　==4270== LEAK SUMMARY:

　　==4270== definitely lost: 10 bytes in 1 blocks.

　　==4270== possibly lost: 0 bytes in 0 blocks.

　　==4270== still reachable: 0 bytes in 0 blocks.

　　==4270== suppressed: 0 bytes in 0 blocks.

　　==4270== Reachable blocks (those to which a pointer was found) are not shown.

　　==4270== To see them, rerun with: --show-reachable=yes

　　从这份报告可以看出，进程号是4270，test.c的第8行写内存越界了，引起写内存越界的是strcpy函数，

　　第7行泄漏了10个字节的内存，引起内存泄漏的是malloc函数。

　　例子二（test2.c)

　　#include <stdio.h>

　　int foo(int x)

　　{

　　if (x < 0) {

　　printf("%d ", x);

　　}

　　return 0;

　　}

　　int main(int argc, char *argv[])

　　{

　　int x;

　　foo(x);

　　return 0;

　　}

　　编译程序

　　gcc -g -o test2 test2.c

　　用valgrind做内存检查

　　valgrind --tool=memcheck ./test2

　　输出报告如下

　　==4285== Memcheck, a memory error detector.

　　==4285== Copyright (C) 2002-2006, and GNU GPL'd, by Julian Seward et al.

　　==4285== Using LibVEX rev 1606, a library for dynamic binary translation.

　　==4285== Copyright (C) 2004-2006, and GNU GPL'd, by OpenWorks LLP.

　　==4285== Using valgrind-3.2.0, a dynamic binary instrumentation framework.

　　==4285== Copyright (C) 2000-2006, and GNU GPL'd, by Julian Seward et al.

　　==4285== For more details, rerun with: -v

　　==4285==

　　==4285== Conditional jump or move depends on uninitialised value(s)

　　==4285== at 0x8048372: foo (test2.c:5)

　　==4285== by 0x80483B4: main (test2.c:16)

　　==4285==p p

　　==4285== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 12 from 1)

　　==4285== malloc/free: in use at exit: 0 bytes in 0 blocks.

　　==4285== malloc/free: 0 allocs, 0 frees, 0 bytes allocated.

　　==4285== For counts of detected errors, rerun with: -v

　　==4285== All heap blocks were freed -- no leaks are possible.