valgrind 简单使用 - yanbin's Blog
valgrind 简单使用
yanbin
posted @ 2015年3月16日 00:03
in Programming
, 1749 阅读
valgrind 是一款 memorycheck 工具，用于 c/c++ 程序的内存检查/调试。
0. 为了使用 valgrind 编译程序时要使用 gcc 的 -g 编译选项，链接libc 的 debug 版本,
自动链接，但是要求有, 如果没有 valgrind 不能正常启动内存检查.
程序用到的其他 C 库也要有 debug 版本的。
也可以使用 gcc 的 -O0 编译选项。据说使用了更好。(大写 O, 数字 0)
自动链接，但是要求有, 如果没有 valgrind 不能正常启动内存检查.
程序用到的其他 C 库也要有 debug 版本的。
也可以使用 gcc 的 -O0 编译选项。据说使用了更好。(大写 O, 数字 0)
-g 是表示编译出的二进制代码中包含调试符号
-O0 是 gcc 的默认选项。可能一些低版本的 gcc 需要加上这个选项。
1. Memorycheck 是 valgrind 的默认工具，--leak-check 选项可以打开 valgrind 详细的 memory leak 探测工具。
$ gcc -O0 -g example.c -o example
$ valgrind --leack-check=yes ./example arg1 arg2
$ gcc -O0 -g example.c -o example
$ valgrind --leack-check=yes ./example arg1 arg2
2. valgrind 的输出。
下面是一个正常分配并正常释放内存的程序用 valgrind 调试的输出:
下面是一个正常分配并正常释放内存的程序用 valgrind 调试的输出:
# 733 是 process id, 无关紧要;
==733== Memcheck, a memory error detector
==733== Copyright (C) 2002-2013, and GNU GPL'd, by Julian Seward et al.
==733== Using Valgrind-3.10.0.SVN and LibVEX; rerun with -h for copyright
info
# 以下是重要信息;
==733== Command: ./mkdir_t 1/2/3/4
==733==
# 这里可能会有程序的 stdout/stderr 输出;
==733==
# 内存使用状况的汇总;
==733== HEAP SUMMARY:
==733== in use at exit: 0 bytes in 0 blocks
==733== total heap usage: 3 allocs, 3 frees, 18 bytes allocated
==733==
==733== All heap blocks were freed -- no leaks are possible
==733==
# 错误信息汇总;(这里没有错误)
==733== For counts of detected and suppressed errors, rerun with: -v
==733== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 2 from 2)
下面是一个越界使用了动态分配的内存, 没有释放动态分配内存的程序的输出;
程序名字是 example, 程序文件名后面的数字说明了 memory allocated 之类的操作的
代码在文件中的位置, 或者说哪里有 memory allocated.
==733== Memcheck, a memory error detector
==733== Copyright (C) 2002-2013, and GNU GPL'd, by Julian Seward et al.
==733== Using Valgrind-3.10.0.SVN and LibVEX; rerun with -h for copyright
info
# 以下是重要信息;
==733== Command: ./mkdir_t 1/2/3/4
==733==
# 这里可能会有程序的 stdout/stderr 输出;
==733==
# 内存使用状况的汇总;
==733== HEAP SUMMARY:
==733== in use at exit: 0 bytes in 0 blocks
==733== total heap usage: 3 allocs, 3 frees, 18 bytes allocated
==733==
==733== All heap blocks were freed -- no leaks are possible
==733==
# 错误信息汇总;(这里没有错误)
==733== For counts of detected and suppressed errors, rerun with: -v
==733== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 2 from 2)
下面是一个越界使用了动态分配的内存, 没有释放动态分配内存的程序的输出;
程序名字是 example, 程序文件名后面的数字说明了 memory allocated 之类的操作的
代码在文件中的位置, 或者说哪里有 memory allocated.
# Invalid write 指示了 memory overrun;
==1058== Invalid write of size 4
# 这里是堆栈跟踪(stack tracking), stack tracking 从下到上读比较容易;
==1058== at 0x40054A: func (example.c:15)
==1058== by 0x400524: main (example.c:8)
==1058== Address 0x51bc068 is 0 bytes after a block of size 40 alloc'd
==1058== Invalid write of size 4
# 这里是堆栈跟踪(stack tracking), stack tracking 从下到上读比较容易;
==1058== at 0x40054A: func (example.c:15)
==1058== by 0x400524: main (example.c:8)
==1058== Address 0x51bc068 is 0 bytes after a block of size 40 alloc'd
# 这里也是 stack tracking 信息，比上面的更深了一层，
# 已经到了 malloc 是内存分配的情况;
==1058== at 0x4C29554: malloc (vg_replace_malloc.c:298)
==1058== by 0x40053D: func (example.c:14) # 后面的数字指示了代码所在行
==1058== by 0x400524: main (example.c:8)
==1058==
==1058==
# 内存(HEAP)，使用汇总;
==1058== HEAP SUMMARY:
==1058== in use at exit: 40 bytes in 1 blocks
# N allocs, N frees 才正常, 40 bytes allocated 指示分配了多少字节内存;
==1058== total heap usage: 1 allocs, 0 frees, 40 bytes allocated
==1058==
# definitely lost 指示了内存泄漏(memory leak);
==1058== 40 bytes in 1 blocks are definitely lost in loss record 1 of 1
==1058== at 0x4C29554: malloc (vg_replace_malloc.c:298)
==1058== by 0x40053D: func (example.c:14)
==1058== by 0x400524: main (example.c:8)
==1058==
# memory leak 汇总;
# definitely, indirectly, possibly 是三种 memory leadk 方式.
==1058== LEAK SUMMARY:
==1058== definitely lost: 40 bytes in 1 blocks # 明确地
==1058== indirectly lost: 0 bytes in 0 blocks # 间接地
==1058== possibly lost: 0 bytes in 0 blocks # 可能性很大地
==1058== still reachable: 0 bytes in 0 blocks
==1058== suppressed: 0 bytes in 0 blocks
==1058==
# 错误信息汇总
==1058== For counts of detected and suppressed errors, rerun with: -v
==1058== ERROR SUMMARY: 2 errors from 2 contexts (suppressed: 2 from 2)
# 已经到了 malloc 是内存分配的情况;
==1058== at 0x4C29554: malloc (vg_replace_malloc.c:298)
==1058== by 0x40053D: func (example.c:14) # 后面的数字指示了代码所在行
==1058== by 0x400524: main (example.c:8)
==1058==
==1058==
# 内存(HEAP)，使用汇总;
==1058== HEAP SUMMARY:
==1058== in use at exit: 40 bytes in 1 blocks
# N allocs, N frees 才正常, 40 bytes allocated 指示分配了多少字节内存;
==1058== total heap usage: 1 allocs, 0 frees, 40 bytes allocated
==1058==
# definitely lost 指示了内存泄漏(memory leak);
==1058== 40 bytes in 1 blocks are definitely lost in loss record 1 of 1
==1058== at 0x4C29554: malloc (vg_replace_malloc.c:298)
==1058== by 0x40053D: func (example.c:14)
==1058== by 0x400524: main (example.c:8)
==1058==
# memory leak 汇总;
# definitely, indirectly, possibly 是三种 memory leadk 方式.
==1058== LEAK SUMMARY:
==1058== definitely lost: 40 bytes in 1 blocks # 明确地
==1058== indirectly lost: 0 bytes in 0 blocks # 间接地
==1058== possibly lost: 0 bytes in 0 blocks # 可能性很大地
==1058== still reachable: 0 bytes in 0 blocks
==1058== suppressed: 0 bytes in 0 blocks
==1058==
# 错误信息汇总
==1058== For counts of detected and suppressed errors, rerun with: -v
==1058== ERROR SUMMARY: 2 errors from 2 contexts (suppressed: 2 from 2)
3. If the stack trace is not big enough, use the --num-callers option to
make it bigger.
make it bigger.
4. valgrind 也报告"使用了未初始化变量错误(uninitialished value)"的情况。
使用 --track-origins=yes 可以看到有关于此的更多的扩展信息,
但是这样也会让程序变得更慢.
使用 --track-origins=yes 可以看到有关于此的更多的扩展信息,
但是这样也会让程序变得更慢.
5. Memcheck cannot detect every memory error your program has.
For example, it can't detect out-of-range reads or writes to arrays
that are allocated statically or on the stack.
But it should detect many errors that could crash your program
(eg. cause a segmentation fault).
For example, it can't detect out-of-range reads or writes to arrays
that are allocated statically or on the stack.
But it should detect many errors that could crash your program
(eg. cause a segmentation fault).
6. 使用 valgrind 调试使用了 GLib 的程序需要加一些 flag.
比如让 GLib 使用 std malloc.
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