Use mtrace () to capture memory leaks

Original article: http://blog.yam.com/ddy1280/article/3064451

Recently, we found that memory leaks exists in the program used by YACC & Lex.
It took some time to complete the division and finally found the problem in YACC & Lex.
Mtrace is a good tool to help me catch these problems. Mtrace is a function provided by gnu c/C ++ (Linux platform ).
Using a ticket with GCC-g in addition to metadata, you can easily find the problem

Example:

 1 #include <stdio.h> 2 #include <stdlib.h> 3  4 int main(int argc, char *argv[]) 5 { 6     int *p; 7     int i; 8  9     #ifdef DEBUG10         setenv("MALLOC_TRACE", "./memleak.log", 1);11         mtrace();12     #endif13 14     p=(int *)malloc(1000);15     if (p!=NULL)16     {17         for (i=0;i<1000;i++)18         {19           p[i]=i;20         }21     }22     else23         printf("malloc fail");24 25     return 0;26 }

Malloc has an empty space in this program, and the memory has not been free. We have added the following code 9 for the Division worker.# Ifdef debug10 setenv ("malloc_trace", "./memleak. log", 1); 11 mtrace (); 12# EndifThen restart gcc-g-o AA-ddebug AA. C.

Rows./AAProgram. After the operation is completed, the./memleak. log file is displayed in the project to view its content,
When the scalability is relatively low, it cannot be seen any problems.

$ Cat memleak. Log = Start @./AA :( mtrace + 0xf9) [0x8048401] + 0x8049ab0 0x3e8 @/Lib/tls/libc. so.6 :( clearenv + 0x7c) [0x42029acc]-0x8049690 @/Lib/tls/libc. so.6 :( tdestroy + 0x39) [0x420dc9e9]-0x8049700 @/Lib/tls/libc. so.6 :( tdestroy + 0x41) [0x420dc9f1]-0x8049728 @/Lib/tls/libc. so.6: [0x42113a22]-0x8049648 @/Lib/tls/libc. so.6: [0x42113a52]-0x8049660 @/Lib/tls/libc. so.6: [0x42113a96]-0x8049678

In this case, you can use the/usr/bin/mtrace tool compiled by Perl to parse the above information.

$ Mtrace AA memleak. Log -0x08049690 free 3 was never alloc 'd 0x42029acc -0x08049700 free 4 was never alloc 'd 0x420dc9e9 -0x08049728 free 5 was never alloc 'd 0x420dc9f1 -0x08049648 free 6 was never alloc 'd 0x42113a22 -0x08049660 free 7 was never alloc 'd 0x42113a52 -0x08049678 free 8 was never alloc 'd 0x42113a96 Memory not freed: ----------------- Address size caller 0x08049ab0 0x3e8 at/home/ddy/test/AA. C: 14

In this way, we can know that there is no corresponding free () for the malloc of the AA. c 14th line ()
By making good use of such tools, you can make the program better stable ^__ ^

<The above programs are not available in GCC 3.2.2 on Linux platform without authorization>

Additional information:
The gnu c library's allocation debugging
Identifying memory leaks in Linux for C ++ programs