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Valgrind工具详解

1.Memcheck

    最常用的工具,用来检测程序中出现的内存问题,所有对内存的读写都会被检测到,一切对malloc、free、new、delete的调用都会被捕获。所以,它能检测以下问题:

       1、对未初始化内存的使用;

       2、读/写释放后的内存块;

       3、读/写超出malloc分配的内存块

       4、读/写不适当的栈中内存块;

       5、内存泄漏,指向一块内存的指针永远丢失;

       6、不正确的malloc/free或new/delete匹配;

       7、memcpy()相关函数中的dst和src指针重叠。

这些问题往往是C/C++程序员最头疼的问题,Memcheck能在这里帮上大忙。

#include<stdio.h>
#include<stdlib.h>
void main()
{
       int *ptr = (int *)0;
       *ptr = 100;
}
~

 

valgrind: m_coredump/coredump-elf.c:495 (fill_fpu): Assertion 'Unimplemented functionality' failed.
valgrind: valgrind

host stacktrace:
==16543==    at 0x5803DBA0: ??? (in /usr/lib/valgrind/memcheck-arm64-linux)

sched status:
  running_tid=1

Thread 1: status = VgTs_Runnable (lwpid 16543)
==16543==    at 0x108778: main (seg.c:6)


Note: see also the FAQ in the source distribution.
It contains workarounds to several common problems.
In particular, if Valgrind aborted or crashed after
identifying problems in your program, there's a good chance
that fixing those problems will prevent Valgrind aborting or
crashing, especially if it happened in m_mallocfree.c.

If that doesn't help, please report this bug to: www.valgrind.org

In the bug report, send all the above text, the valgrind
version, and what OS and version you are using.  Thanks.

 

 1 #include <stdio.h>
 2 #include <stdlib.h>
 3 
 4 void test(void)
 5 {
 6     int *buf = malloc(10 * sizeof(int));
 7     buf[10] = 0x55;
 8 }
 9 
10 int main(void)
11 {
12     test();
13     return 0;
14 }

 

root@ubuntu:~/c++#  gcc mem_check.c -o mem_check -g -O0
root@ubuntu:~/c++# valgrind --leak-check=yes ./mem_check
==18896== Memcheck, a memory error detector
==18896== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==18896== Using Valgrind-3.13.0 and LibVEX; rerun with -h for copyright info
==18896== Command: ./mem_check
==18896== 
==18896== Invalid write of size 4
==18896==    at 0x1087D8: test (mem_check.c:7)
==18896==    by 0x1087F3: main (mem_check.c:12)
==18896==  Address 0x49cc068 is 0 bytes after a block of size 40 alloc'd
==18896==    at 0x4845BFC: malloc (in /usr/lib/valgrind/vgpreload_memcheck-arm64-linux.so)
==18896== 
==18896== 
==18896== HEAP SUMMARY:
==18896==     in use at exit: 40 bytes in 1 blocks
==18896==   total heap usage: 1 allocs, 0 frees, 40 bytes allocated
==18896== 
==18896== 40 bytes in 1 blocks are definitely lost in loss record 1 of 1
==18896==    at 0x4845BFC: malloc (in /usr/lib/valgrind/vgpreload_memcheck-arm64-linux.so)
==18896== 
==18896== LEAK SUMMARY:
==18896==    definitely lost: 40 bytes in 1 blocks
==18896==    indirectly lost: 0 bytes in 0 blocks
==18896==      possibly lost: 0 bytes in 0 blocks
==18896==    still reachable: 0 bytes in 0 blocks
==18896==         suppressed: 0 bytes in 0 blocks
==18896== 
==18896== For counts of detected and suppressed errors, rerun with: -v
==18896== ERROR SUMMARY: 2 errors from 2 contexts (suppressed: 0 from 0)

 

root@ubuntu:~/c++# valgrind --leak-check=full ./mem_check2
==24852== Memcheck, a memory error detector
==24852== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==24852== Using Valgrind-3.13.0 and LibVEX; rerun with -h for copyright info
==24852== Command: ./mem_check2
==24852== 
==24852== Invalid write of size 4    // 内存越界  
==24852==    at 0x108868: test (in /root/c++/mem_check2)
==24852==  Address 0x49cc068 is 0 bytes after a block of size 40 alloc'd
==24852==    at 0x4845BFC: malloc (in /usr/lib/valgrind/vgpreload_memcheck-arm64-linux.so)
==24852== 
==24852== Source and destination overlap in memcpy(0x49cc044, 0x49cc040, 5)  // 踩内存  
==24852==    at 0x484B080: __GI_memcpy (in /usr/lib/valgrind/vgpreload_memcheck-arm64-linux.so)
==24852== 
==24852== Invalid free() / delete / delete[] / realloc() // 重复释放  
==24852==    at 0x4846D58: free (in /usr/lib/valgrind/vgpreload_memcheck-arm64-linux.so)
==24852==  Address 0x49cc040 is 0 bytes inside a block of size 40 free'd
==24852==    at 0x4846D58: free (in /usr/lib/valgrind/vgpreload_memcheck-arm64-linux.so)
==24852==  Block was alloc'd at
==24852==    at 0x4845BFC: malloc (in /usr/lib/valgrind/vgpreload_memcheck-arm64-linux.so)
==24852== 
==24852== Use of uninitialised value of size 8
==24852==    at 0x108898: test (in /root/c++/mem_check2)   // 非法指针  
==24852== 
==24852== 
==24852== Process terminating with default action of signal 11 (SIGSEGV): dumping core  //由于非法指针赋值导致的程序崩溃  
==24852==  Bad permissions for mapped region at address 0x48936E4
==24852==    at 0x108898: test (in /root/c++/mem_check2)

valgrind: m_coredump/coredump-elf.c:495 (fill_fpu): Assertion 'Unimplemented functionality' failed.
valgrind: valgrind

host stacktrace:
==24852==    at 0x5803DBA0: ??? (in /usr/lib/valgrind/memcheck-arm64-linux)

sched status:
  running_tid=1

Thread 1: status = VgTs_Runnable (lwpid 24852)
==24852==    at 0x108898: test (in /root/c++/mem_check2)


Note: see also the FAQ in the source distribution.
It contains workarounds to several common problems.
In particular, if Valgrind aborted or crashed after
identifying problems in your program, there's a good chance
that fixing those problems will prevent Valgrind aborting or
crashing, especially if it happened in m_mallocfree.c.

If that doesn't help, please report this bug to: www.valgrind.org

In the bug report, send all the above text, the valgrind
version, and what OS and version you are using.  Thanks.

 

 

#include <stdlib.h>
#include <malloc.h>
#include <string.h>

void test()
{
    int *ptr = malloc(sizeof(int)*10);
    memcpy(ptr +1, ptr, 5); // 踩内存  
    free(ptr);

}

int main(void)
{
    test();
    return 0;
}

运行没报错

root@ubuntu:~/c++# gcc mem_check2.c  -o mem_check2
root@ubuntu:~/c++# ./mem_check2
root@ubuntu:~/c++# 

 

标签:18896,mem,bytes,valgrind,c++,24852
来源: https://www.cnblogs.com/dream397/p/14813456.html