Linux C 编程内存泄露检测工具(一):mtrace
前言 所有使用动态内存分配(dynamic memory allocation)的程序都有机会遇上内存泄露(memory leakage)问题,在Linux里有三种常用工具来检测内存泄露的情況,包括: mtrace dmalloc memwatch 1. mtrace mtrace是三款工具之中是最简单易用的,mtrace是一个C函數,在<mcheck.h>里声明及定义,函数原型为: void mtrace(void); 其实mtrace是类似malloc_hook的 malloc handler,只不过mtrace的handler function已由系统为你写好,但既然如此,系统又怎么知道你想将malloc/free的记录写在哪里呢?为此,调用mtrace()前要先设置 MALLOC_TRACE环境变量: #include <stdlib.h> .... setenv("MALLOC_TRACE", "output_file_name", 1); ... 「output_file_name」就是储存检测结果的文件的名称。 但是检测结果的格式是一般人无法理解的,而只要有安装mtrace的话,就会有一名为mtrace的Perl script,在shell输入以下指令: mtrace [binary] output_file_name 就会将output_file_name的內容转化成能被理解的语句,例如「No memory leaks」,「0x12345678 Free 10 was never alloc」诸如此类。 例如以下有一函数:(暂且放下single entry single exit的原则) #include <stdio.h> #include <stdlib.h> #include <errno.h> #include <mcheck.h> int main() { char *hello; setenv("MALLOC_TRACE", "output", 1); mtrace(); if ((hello = (char *) malloc(sizeof(char))) == NULL) { perror("Cannot allocate memory."); return -1; } return 0; } 执行后,再用mtrace 将结果输出: - 0x08049670 Free 3 was never alloc'd 0x42029acc - 0x080496f0 Free 4 was never alloc'd 0x420dc9e9 - 0x08049708 Free 5 was never alloc'd 0x420dc9f1 - 0x08049628 Free 6 was never alloc'd 0x42113a22 - 0x08049640 Free 7 was never alloc'd 0x42113a52 - 0x08049658 Free 8 was never alloc'd 0x42113a96 Memory not freed: ----------------- Address Size Caller 0x08049a90 0x1 at 0x80483fe 最后一行标明有一个大小为1 byte的内存尚未释放,大概是指「hello」吧。 若我们把该段内存释放: #include <stdio.h> #include <stdlib.h> #include <errno.h> #include <mcheck.h> int main() { char *hello; setenv("MALLOC_TRACE", "output", 1); mtrace(); if ((hello = (char *) malloc(sizeof(char))) == NULL) { perror("Cannot allocate memory."); return -1; } free(hello); return 0; } 结果如下: - 0x080496b0 Free 4 was never alloc'd 0x42029acc - 0x08049730 Free 5 was never alloc'd 0x420dc9e9 - 0x08049748 Free 6 was never alloc'd 0x420dc9f1 - 0x08049668 Free 7 was never alloc'd 0x42113a22 - 0x08049680 Free 8 was never alloc'd 0x42113a52 - 0x08049698 Free 9 was never alloc'd 0x42113a96 No memory leaks. mtrace的原理是记录每一对malloc-free的执行,若每一个malloc都有相应的free,则代表没有内存泄露,对于任何非malloc/free情況下所发生的内存泄露问题,mtrace并不能找出来。
posted on 2015-11-20 17:06 zyz913614263 阅读(535) 评论(0) 编辑 收藏 举报