利用efence调试内存泄漏

男娘i 2022-03-31 02:38 446阅读 0赞

1.What is efence

It attempts to use the virtual memory facilities of Linux to protect the memory used by malloc and free to halt the program at the point of memory corruption.

2. How to install

a). Get the source from the address: http://perens.com/FreeSoftware/ElectricFence/

b). use command tar to decomprss the file

c). just make >> make install >> make clean

3. How to use

a). Get a test file, which can be like below:

#include <stdio.h>
    #include <stdlib.h>
    int main()
    {
            char *ptr = (char *) malloc(1024);
            ptr[0] = 0;
            /* Now write beyond the block */
            ptr[1024] = 0;
            exit(0);
    }

b). Use different way to compile it and check the effect

>>normal way without efence:

test way 1:

gcc -o test test.c

run command ./test and the result is just fine, no error return.

test way 2:

use gdb to run test, it need to be recompilled

gcc -g -o test test.c

run command gdb ./test then input commandrun the result as below :

Starting program: /home/test  
\[Inferior 1 (process 23732) exited normally\]  
Missing separate debuginfos, use: debuginfo-install glibc-2.14.90-24.fc16.9.i686

>>use the efence library

test way 1:

gcc -o test test.c -lefence -lpthread

run command ./test and the result is below:

test way 2:

gcc -g -o test test.c -lefence -lpthread

run command gdb ./test then input commandrun the result as below :

Starting program: /home/test  
\[Thread debugging using libthread\_db enabled\]  
Using host libthread\_db library "/lib/libthread\_db.so.1".  
  
Electric Fence 2.1 Copyright (C) 1987-1998 Bruce Perens.  
  
Program received signal SIGSEGV, Segmentation fault.  
0x0804889d in main () at test.c:8  
8 ptr\[1024\] = 0;  
Missing separate debuginfos, use: debuginfo-install glibc-2.14.90-24.fc16.9.i686

4.summary

Use the efence can easily to find out the risk of memory .