用valgrind检查内存问题

Valgrind

Valgrind作为一个免费且优秀的工具包，平时大部分人可能都是使用valgrind检测内存问题，如内存泄露，越界等。

Valgrind工具包包含多个工具，如Memcheck,Cachegrind,Helgrind, Callgrind，Massif。下面分别介绍个工具的作用：

Memcheck　

使用未初始化的内存 (Use of uninitialised memory)
使用已经释放了的内存 (Reading/writing memory after it has been free’d)
使用超过 malloc分配的内存空间(Reading/writing off the end of malloc’d blocks)
对堆栈的非法访问 (Reading/writing inappropriate areas on the stack)
申请的空间是否有释放 (Memory leaks – where pointers to malloc’d blocks are lost forever)
malloc/free/new/delete申请和释放内存的匹配(Mismatched use of malloc/new/new [] vs free/delete/delete [])
src和dst的重叠(Overlapping src and dst pointers in memcpy() and related functions

Callgrind

　　Callgrind收集程序运行时的一些数据，函数调用关系等信息，还可以有选择地进行cache 模拟。在运行结束时，它会把分析数据写入一个文件。callgrind_annotate可以把这个文件的内容转化成可读的形式。

Cachegrind

　　它模拟 CPU中的一级缓存I1,D1和L2二级缓存，能够精确地指出程序中 cache的丢失和命中。如果需要，它还能够为我们提供cache丢失次数，内存引用次数，以及每行代码，每个函数，每个模块，整个程序产生的指令数。这对优化程序有很大的帮助。

Helgrind

　　它主要用来检查多线程程序中出现的竞争问题。Helgrind 寻找内存中被多个线程访问，而又没有一贯加锁的区域，这些区域往往是线程之间失去同步的地方，而且会导致难以发掘的错误。Helgrind实现了名为” Eraser” 的竞争检测算法，并做了进一步改进，减少了报告错误的次数。

Massif

　　堆栈分析器，它能测量程序在堆栈中使用了多少内存，告诉我们堆块，堆管理块和栈的大小。Massif能帮助我们减少内存的使用，在带有虚拟内存的现代系统中，它还能够加速我们程序的运行，减少程序停留在交换区中的几率。

Valgrind使用举例

example.c

 #include<stdio.h>

 #include<stdlib.h>

 int main()

 {

     int a[];   //4*100=400bytes,stack

     int *b = malloc(sizeof(int) * );    //4*100=400bytes,heap   有错误，没有释放内存

     return ;

 }

安装及使用(Ubuntu16.04)

 /*安装Valgrind*/

 sudo apt install valgrind

 /*编译源程序*/

 gcc example.c -o example

 /*输入valgrind的有关命令*/

 /*默认为tool=memcheck*/

 valgrind ./example

 ==== Memcheck, a memory error detector

 ==== Copyright (C) -, and GNU GPL'd, by Julian Seward et al.

 ==== Using Valgrind-3.11. and LibVEX; rerun with -h for copyright info

 ==== Command: ./example

 ====

 ====

 ==== HEAP SUMMARY:

 ====     in use at exit:  bytes in  blocks

 ====   total heap usage:  allocs,  frees,  bytes allocated

 ====

 ==== LEAK SUMMARY:

 ====    definitely lost:  bytes in  blocks

 ====    indirectly lost:  bytes in  blocks

 ====      possibly lost:  bytes in  blocks

 ====    still reachable:  bytes in  blocks

 ====         suppressed:  bytes in  blocks

 ==== Rerun with --leak-check=full to see details of leaked memory

 ====

 ==== For counts of detected and suppressed errors, rerun with: -v

 ==== ERROR SUMMARY:  errors from  contexts (suppressed:  from )

 /*--leak-check=full可以看内存泄漏的细节*/

 valgrind --tool=memcheck --leak-check=full ./example

 ==3152== Memcheck, a memory error detector

 ==3152== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.

 ==3152== Using Valgrind-3.11.0 and LibVEX; rerun with -h for copyright info

 ==3152== Command: ./example

 ==3152==

 ==3152==

 ==3152== HEAP SUMMARY:

 ==3152==     in use at exit: 400 bytes in 1 blocks

 ==3152==   total heap usage: 1 allocs, 0 frees, 400 bytes allocated

 ==3152==

 ==3152== 400 bytes in 1 blocks are definitely lost in loss record 1 of 1    //显示了malloc分配的内存泄露

 ==3152==    at 0x4C2DB8F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)

 ==3152==    by 0x4005B9: main (in /home/rogn/Desktop/MyCode/example)

 ==3152==

 ==3152== LEAK SUMMARY:

 ==3152==    definitely lost: 400 bytes in 1 blocks

 ==3152==    indirectly lost: 0 bytes in 0 blocks

 ==3152==      possibly lost: 0 bytes in 0 blocks

 ==3152==    still reachable: 0 bytes in 0 blocks

 ==3152==         suppressed: 0 bytes in 0 blocks

 ==3152==

 ==3152== For counts of detected and suppressed errors, rerun with: -v

 /*上面只能看到堆内存*/

 /*使用--tool=massif查看堆栈内存*/

 rogn@ubuntu:~/Desktop/MyCode$ valgrind --tool=massif ./example

 ==== Massif, a heap profiler

 ==== Copyright (C) -, and GNU GPL'd, by Nicholas Nethercote

 ==== Using Valgrind-3.11. and LibVEX; rerun with -h for copyright info

 ==== Command: ./example

 ====

 ====

 rogn@ubuntu:~/Desktop/MyCode$ ls

 example  example.c  massif.out.

 rogn@ubuntu:~/Desktop/MyCode$ ms_print massif.out.

 --------------------------------------------------------------------------------

 Command:            ./example

 Massif arguments:   (none)

 ms_print arguments: massif.out.

 --------------------------------------------------------------------------------

      B

   ^                                                                       :

      |                                                                       :

      |                                                                       :

      |                                                                       :

      |                                                                       :

      |                                                                       :

      |                                                                       :

      |                                                                       :

      |                                                                       :

      |                                                                       :

      |                                                                       :

      |                                                                       :

      |                                                                       :

      |                                                                       :

      |                                                                       :

      |                                                                       :

      |                                                                       :

      |                                                                       :

      |                                                                       :

      |                                                                       :

     +----------------------------------------------------------------------->ki

                                                                         102.0

 Number of snapshots:

  Detailed snapshots: []

 --------------------------------------------------------------------------------

   n        time(i)         total(B)   useful-heap(B) extra-heap(B)    stacks(B)

 --------------------------------------------------------------------------------

           ,                                                     

 /*查看整个程序使用的内存和时间*/

 rogn@ubuntu:~/Desktop/MyCode$ valgrind --tool=massif --pages-as-heap=yes ./example

 ==== Massif, a heap profiler

 ==== Copyright (C) -, and GNU GPL'd, by Nicholas Nethercote

 ==== Using Valgrind-3.11. and LibVEX; rerun with -h for copyright info

 ==== Command: ./example

 ====

 ====

 rogn@ubuntu:~/Desktop/MyCode$ ls        //查看当前目录下的文件，发现多了一个名叫massif.out.3191的文件（3191其实就是PID）

 example  example.c  massif.out.  massif.out.

 rogn@ubuntu:~/Desktop/MyCode$ ms_print massif.out.3191   //使用ms_print程序打印出massif.out.391

 --------------------------------------------------------------------------------

 Command:            ./example

 Massif arguments:   --pages-as-heap=yes

 ms_print arguments: massif.out.

 --------------------------------------------------------------------------------

     MB

 6.172^  //这个就是总的内存了，所谓的Memory limit就是指这个                                                                     :

      |      ::@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@#:::::::::::::::::::::::::::::

      |      : @                                 #                            :

      |      : @                                 #                            :

      |      : @                                 #                            :

      |      : @                                 #                            :

      |      : @                                 #                            :

      |      : @                                 #                            :

      |      : @                                 #                            :

      |      : @                                 #                            :

      |      : @                                 #                            :

      |      : @                                 #                            :

      |      : @                                 #                            :

      |   :::: @                                 #                            :

      |   :::: @                                 #                            :

      |   :::: @                                 #                            :

      |   :::: @                                 #                            :

      |   :::: @                                 #                            :

      |   :::: @                                 #                            :

      |   :::: @                                 #                            :

     +----------------------------------------------------------------------->ki

                                                                         148.4  //运行时间，单位是ms

 Number of snapshots:

  Detailed snapshots: [, , ,  (peak)]

 --------------------------------------------------------------------------------

   n        time(i)         total(B)   useful-heap(B) extra-heap(B)    stacks(B)

 --------------------------------------------------------------------------------

                             ,            ,

                            ,           ,

                           ,          ,

                           ,          ,

                           ,          ,

                           ,          ,

                           ,          ,

                           ,          ,

                           ,          ,

                           ,          ,

 100.00% (,800B) (page allocation syscalls) mmap/mremap/brk, --alloc-fns, etc.

 ->98.00% (,704B) 0xFFFFFFFFFFFFFFFF: ???

 |

 ->02.00% (,096B) 0x4000C2F: ??? (in /lib/x86_64-linux-gnu/ld-2.23.so)

 --------------------------------------------------------------------------------

   n        time(i)         total(B)   useful-heap(B) extra-heap(B)    stacks(B)

 --------------------------------------------------------------------------------

                          ,          ,

 100.00% (,800B) (page allocation syscalls) mmap/mremap/brk, --alloc-fns, etc.

 ->98.00% (,704B) 0xFFFFFFFFFFFFFFFF: ???

 |

 ->02.00% (,096B) 0x4000C2F: ??? (in /lib/x86_64-linux-gnu/ld-2.23.so)

 --------------------------------------------------------------------------------

   n        time(i)         total(B)   useful-heap(B) extra-heap(B)    stacks(B)

 --------------------------------------------------------------------------------

                          ,          ,

                          ,          ,

            ,        ,,        ,,

            ,        ,,        ,,

           ,        ,,        ,,

           ,        ,,        ,,

           ,        ,,        ,,

           ,        ,,        ,,

           ,        ,,        ,,

           ,        ,,        ,,

 100.00% (,,528B) (page allocation syscalls) mmap/mremap/brk, --alloc-fns, etc.

 ->96.88% (,,824B) 0x401B4B9: mmap (mmap.c:)

 | ->94.64% (,,464B) 0x40068CB: _dl_map_object_from_fd (dl-map-segments.h:)

 | | ->94.64% (,,464B) 0x4008C25: _dl_map_object (dl-load.c:)

 | |   ->61.86% (,,120B) 0x400DBA0: openaux (dl-deps.c:)

 | |   | ->61.86% (,,120B) 0x4010562: _dl_catch_error (dl-error.c:)

 | |   |   ->61.86% (,,120B) 0x400E1E0: _dl_map_object_deps (dl-deps.c:)

 | |   |     ->61.86% (,,120B) 0x4003A27: dl_main (rtld.c:)

 | |   |       ->61.86% (,,120B) 0x4019630: _dl_sysdep_start (dl-sysdep.c:)

 | |   |         ->61.86% (,,120B) 0x4001C28: _dl_start (rtld.c:)

 | |   |           ->61.86% (,,120B) 0x4000C36: ??? (in /lib/x86_64-linux-gnu/ld-2.23.so)

 | |   |

 | |   ->32.78% (,,344B) 0x4000EB3: map_doit (rtld.c:)

 | |     ->32.78% (,,344B) 0x4010562: _dl_catch_error (dl-error.c:)

 | |       ->32.78% (,,344B) 0x40020D4: handle_ld_preload (rtld.c:)

 | |         ->32.78% (,,344B) 0x40039AD: dl_main (rtld.c:)

 | |           ->32.78% (,,344B) 0x4019630: _dl_sysdep_start (dl-sysdep.c:)

 | |             ->32.78% (,,344B) 0x4001C28: _dl_start (rtld.c:)

 | |               ->32.78% (,,344B) 0x4000C36: ??? (in /lib/x86_64-linux-gnu/ld-2.23.so)

 | |

 | ->01.34% (,016B) 0x4011773: _dl_sysdep_read_whole_file (dl-misc.c:)

 | | ->01.34% (,016B) 0x4018506: _dl_load_cache_lookup (dl-cache.c:)

 | |   ->01.34% (,016B) 0x4009167: _dl_map_object (dl-load.c:)

 | |     ->01.34% (,016B) 0x400DBA0: openaux (dl-deps.c:)

 | |       ->01.34% (,016B) 0x4010562: _dl_catch_error (dl-error.c:)

 | |         ->01.34% (,016B) 0x400E1E0: _dl_map_object_deps (dl-deps.c:)

 | |           ->01.34% (,016B) 0x4003A27: dl_main (rtld.c:)

 | |             ->01.34% (,016B) 0x4019630: _dl_sysdep_start (dl-sysdep.c:)

 | |               ->01.34% (,016B) 0x4001C28: _dl_start (rtld.c:)

 | |                 ->01.34% (,016B) 0x4000C36: ??? (in /lib/x86_64-linux-gnu/ld-2.23.so)

 | |

 | ->00.89% (,344B) in + places, all below ms_print's threshold (01.00%)

 |

 ->03.12% (,704B) 0xFFFFFFFFFFFFFFFF: ???

 |

 ->00.00% (0B) in + places, all below ms_print's threshold (01.00%)

 --------------------------------------------------------------------------------

   n        time(i)         total(B)   useful-heap(B) extra-heap(B)    stacks(B)

 --------------------------------------------------------------------------------

           ,        ,,        ,,

 100.00% (,,608B) (page allocation syscalls) mmap/mremap/brk, --alloc-fns, etc.

 ->96.83% (,,904B) 0x401B4B9: mmap (mmap.c:)

 | ->95.87% (,,464B) 0x40068CB: _dl_map_object_from_fd (dl-map-segments.h:)

 | | ->95.87% (,,464B) 0x4008C25: _dl_map_object (dl-load.c:)

 | |   ->62.66% (,,120B) 0x400DBA0: openaux (dl-deps.c:)

 | |   | ->62.66% (,,120B) 0x4010562: _dl_catch_error (dl-error.c:)

 | |   |   ->62.66% (,,120B) 0x400E1E0: _dl_map_object_deps (dl-deps.c:)

 | |   |     ->62.66% (,,120B) 0x4003A27: dl_main (rtld.c:)

 | |   |       ->62.66% (,,120B) 0x4019630: _dl_sysdep_start (dl-sysdep.c:)

 | |   |         ->62.66% (,,120B) 0x4001C28: _dl_start (rtld.c:)

 | |   |           ->62.66% (,,120B) 0x4000C36: ??? (in /lib/x86_64-linux-gnu/ld-2.23.so)

 | |   |

 | |   ->33.20% (,,344B) 0x4000EB3: map_doit (rtld.c:)

 | |     ->33.20% (,,344B) 0x4010562: _dl_catch_error (dl-error.c:)

 | |       ->33.20% (,,344B) 0x40020D4: handle_ld_preload (rtld.c:)

 | |         ->33.20% (,,344B) 0x40039AD: dl_main (rtld.c:)

 | |           ->33.20% (,,344B) 0x4019630: _dl_sysdep_start (dl-sysdep.c:)

 | |             ->33.20% (,,344B) 0x4001C28: _dl_start (rtld.c:)

 | |               ->33.20% (,,344B) 0x4000C36: ??? (in /lib/x86_64-linux-gnu/ld-2.23.so)

 | |

 | ->00.97% (,440B) in + places, all below ms_print's threshold (01.00%)

 |

 ->03.17% (,704B) 0xFFFFFFFFFFFFFFFF: ???

 |

 ->00.00% (0B) in + places, all below ms_print's threshold (01.00%)

 --------------------------------------------------------------------------------

   n        time(i)         total(B)   useful-heap(B) extra-heap(B)    stacks(B)

 --------------------------------------------------------------------------------

           ,        ,,        ,,

          ,        ,,        ,,

参考链接：

https://youtu.be/kjkrpgWr9G4

https://blog.csdn.net/kesalin/article/details/2593958

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