您可以在代码中使用一些技术来检测内存泄漏。最常见和最简单的检测方法是，定义一个宏(比如DEBUG_NEW)，并使用它与预定义的宏(如__FILE__和__LINE__)一起定位代码中的内存泄漏。这些预定义的宏告诉您内存泄漏的文件号和行号。

DEBUG_NEW只是一个宏，通常定义为:

#define DEBUG_NEW new(__FILE__, __LINE__)
#define new DEBUG_NEW

因此，无论在哪里使用new，它都可以跟踪文件和行号，这可以用来定位程序中的内存泄漏。

而__FILE__， __LINE__是预定义的宏，它们分别计算你使用它们的文件名和行号!

阅读下面的文章，它解释了使用DEBUG_NEW和其他有趣的宏的技术，非常漂亮:

一个跨平台的内存泄漏检测器

---

从Wikpedia,

Debug_new refers to a technique in C++ to overload and/or redefine operator new and operator delete in order to intercept the memory allocation and deallocation calls, and thus debug a program for memory usage. It often involves defining a macro named DEBUG_NEW, and makes new become something like new(_FILE_, _LINE_) to record the file/line information on allocation. Microsoft Visual C++ uses this technique in its Microsoft Foundation Classes. There are some ways to extend this method to avoid using macro redefinition while still able to display the file/line information on some platforms. There are many inherent limitations to this method. It applies only to C++, and cannot catch memory leaks by C functions like malloc. However, it can be very simple to use and also very fast, when compared to some more complete memory debugger solutions.

在Windows上，你可以使用CRT调试堆。

是否有任何标准或程序可以确保程序中没有内存泄漏。

是的，不要使用手动内存管理(如果你曾经手动调用delete或delete[]，那么你做错了)。使用RAII和智能指针，将堆分配限制到绝对最小值(大多数时候，自动变量就足够了)。

如果使用gcc，则有gprof可用。

我想知道程序员如何发现内存泄漏

有些人使用工具，有些人做你做的事情，也可以通过同行代码审查

是否应该遵循某种标准或过程来确保程序中没有内存泄漏

对我来说:每当我创建动态分配对象时，我总是把释放代码放在后面，然后在中间填充代码。如果您确定之间的代码中不会出现异常，那么这样做是可以的。否则，我会使用try-finally(我不经常使用c++)。

Search your code for occurrences of new, and make sure that they all occur within a constructor with a matching delete in a destructor. Make sure that this is the only possibly throwing operation in that constructor. A simple way to do this is to wrap all pointers in std::auto_ptr, or boost::scoped_ptr (depending on whether or not you need move semantics). For all future code just ensure that every resource is owned by an object that cleans up the resource in its destructor. If you need move semantics then you can upgrade to a compiler that supports r-value references (VS2010 does I believe) and create move constructors. If you don't want to do that then you can use a variety of tricky techniques involving conscientious usage of swap, or try the Boost.Move library.

Download Debugging Tools for Windows. Use the gflags utility to turn on user-mode stack traces. Use UMDH to take multiple snapshots of your program's memory. Take a snapshot before memory gets allocated, and take a second snapshot after a point at which you believe that your program has leaked memory. You might want to add pauses or prompts in your program to give you a chance to run UMDH and take the snapshots. Run UMDH again, this time in its mode that does a diff between the two snapshots. It will then generate a report containing the call stacks of suspected memory leaks. Restore your previous gflags settings when you're done.

UMDH会给你比CRT调试堆更多的信息，因为它会监视整个进程的内存分配;它甚至可以告诉您第三方组件是否泄漏。

有一些著名的编程技术可以帮助您将内存泄漏的风险降至最低:

if you have to do your own dynamic memory allocation, write new and delete always pairwise, and make sure the allocation/deallocation code is called pairwise avoid dynamic memory allocation if you can. For example, use vector<T> t whereever possible instead of T* t = new T[size] use "smart pointers" like boost smart pointers (http://www.boost.org/doc/libs/1_46_1/libs/smart_ptr/smart_ptr.htm) my personal favorite: make sure you have understood the concept of ownership of a pointer, and make sure that everywhere where you use pointers, you know which code entity is the owner learn which constructors / assignment operators are automatically created by the C++ compiler, and what that means if you have class that owns a pointer (or what that means if you have a class that contains a pointer to an object it does not own).

在visual studio中，有一个内置的内存泄漏检测器，称为C运行时库。当主函数返回后程序退出时，CRT将检查应用程序的调试堆。如果在调试堆上仍然分配了任何块，那么就存在内存泄漏。 本论坛讨论了在C/ c++中避免内存泄漏的一些方法。

回答你问题的第二部分，

是否有任何标准或程序可以确保程序中没有内存泄漏。

是的，有。这是C和c++的主要区别之一。

在c++中，永远不要在用户代码中调用new或delete。RAII是一种非常常用的技术，它在很大程度上解决了资源管理问题。程序中的每一个资源(资源是任何需要获取，然后释放的东西:文件句柄，网络套接字，数据库连接，但也包括普通内存分配，在某些情况下，对API调用(BeginX()/EndX()， LockY()， UnlockY()))都应该包装在一个类中，其中:

构造函数获取资源(如果资源是内存分配，则调用new) 析构函数释放资源， 复制和赋值要么被阻止(通过将复制构造函数和赋值操作符设置为私有)，要么被实现为正确工作(例如通过克隆底层资源)

然后，该类在本地、堆栈上或作为类成员实例化，而不是通过调用new和存储指针来实例化。

You often don't need to define these classes yourself. The standard library containers behave in this way as well, so that any object stored into a std::vector gets freed when the vector is destroyed. So again, don't store a pointer into the container (which would require you to call new and delete), but rather the object itself (which gives you memory management for free). Likewise, smart pointer classes can be used to easily wrap objects that just have to be allocated with new, and control their lifetimes.

这意味着当对象超出作用域时，它将被自动销毁，并释放和清理它的资源。

如果在整个代码中始终这样做，就不会有任何内存泄漏。所有可能泄露的内容都绑定到析构函数，该析构函数保证在控件离开声明对象的作用域时被调用。

指令

你需要的东西

熟练使用c++ c++编译器 调试器和其他调查软件工具

1

理解操作符的基础知识。c++操作符new分配堆内存。delete操作符释放堆内存。对于每一个new，你应该使用delete来释放你分配的内存:

char* str = new char [30]; // Allocate 30 bytes to house a string.

delete [] str; // Clear those 30 bytes and make str point nowhere.

2

仅在删除时重新分配内存。在下面的代码中，str通过第二次分配获得了一个新地址。第一个地址将不可挽回地丢失，它所指向的30个字节也将丢失。现在他们不可能被释放，你有一个内存泄漏:

char* str = new char [30]; // Give str a memory address.

// delete [] str; // Remove the first comment marking in this line to correct.

str = new char [60]; /* Give str another memory address with
                                                    the first one gone forever.*/

delete [] str; // This deletes the 60 bytes, not just the first 30.

3

注意那些指针的赋值。每个动态变量(在堆上分配内存)都需要与一个指针相关联。当一个动态变量与其指针分离时，它就不可能被删除。同样，这会导致内存泄漏:

char* str1 = new char [30];

char* str2 = new char [40];

strcpy(str1, "Memory leak");

str2 = str1; // Bad! Now the 40 bytes are impossible to free.

delete [] str2; // This deletes the 30 bytes.

delete [] str1; // Possible access violation. What a disaster!

4

小心使用局部指针。在函数中声明的指针分配在堆栈上，但它所指向的动态变量分配在堆上。如果你不删除它，它将在程序退出函数后继续存在:

void Leak(int x){

char* p = new char [x];

// delete [] p; // Remove the first comment marking to correct.

}

5

注意“delete”后面的方括号。使用delete本身来释放单个对象。使用带方括号的delete[]来释放堆数组。不要做这样的事情:

char* one = new char;

delete [] one; // Wrong

char* many = new char [30];

delete many; // Wrong!

6

如果泄漏还允许-我通常寻求它与deleaker(检查这里:http://deleaker.com)。

Valgrind http://valgrind.org/

and

广东发展银行 http://www.gnu.org/software/gdb/

Visual Leak Detector (VLD)是一个免费的、健壮的、开源的Visual c++内存泄漏检测系统。

当您在Visual Studio调试器下运行程序时，Visual Leak Detector将在调试会话结束时输出内存泄漏报告。泄漏报告包括完整的调用堆栈，显示泄漏的内存块是如何分配的。双击调用堆栈中的一行，以跳转到编辑器窗口中的该文件和该行。

如果你只有崩溃转储，你可以使用Windbg !heap -l命令，它将检测泄漏的堆块。最好打开gflags选项:“创建用户模式堆栈跟踪数据库”，然后您将看到内存分配调用堆栈。

AddressSanitizer (ASan)是一种快速的内存错误检测器。 它可以发现C/ c++程序中的use-after-free和{heap,stack,global}-buffer溢出错误。它发现:

在free之后使用(悬空指针解引用) 堆缓冲区溢出 堆栈缓冲区溢出 全局缓冲区溢出 退货后使用 初始化顺序错误

这个工具很快。仪器程序的平均速度为~2倍。

MTuner是一个免费的多平台内存分析、泄漏检测和分析工具，支持MSVC、GCC和Clang编译器。功能包括:

基于时间轴的内存使用历史和活动内存块 强大的内存操作过滤基于堆，内存标签，时间范围等。 SDK手动仪表与完整的源代码 通过命令行使用支持持续集成 调用堆栈树和树映射导航 更多。

用户可以通过GCC或Clang cross配置任何软件定位平台 编译器。MTuner内置对Windows、PlayStation 4和PlayStation 3平台的支持。

运行“Valgrind”可以:

1)帮助识别内存泄漏-显示您有多少内存泄漏，并指出代码中泄漏内存分配的行。

2)指出错误的释放内存的尝试(例如不正确的delete调用)

“Valgrind”使用说明

1)在这里获得valgrind。

2)使用-g标志编译代码

3)在shell中运行:

valgrind --leak-check=yes myprog arg1 arg2

其中"myprog"是你编译的程序，arg1, arg2是你程序的参数。

4)结果是一个调用malloc/new的列表，没有后续调用free delete。

例如:

==4230==    at 0x1B977DD0: malloc (vg_replace_malloc.c:136)

==4230==    by 0x804990F: main (example.c:6)

告诉您在哪一行(未释放的)调用了malloc。

正如其他人指出的那样，确保对于每个新的/malloc调用，都有一个后续的delete/free调用。

除了其他答案中提供的工具和方法之外，静态代码分析工具还可以用于检测内存泄漏(以及其他问题)。 Cppcheck是一个免费的健壮的工具。但是还有很多其他可用的工具。Wikipedia有一个静态代码分析工具列表。

在应用程序代码中不应该使用“new”或“delete”。相反，应该创建一个使用管理器/工作人员习惯用法的新类型，其中管理器类分配和释放内存，并将所有其他操作转发给工作人员对象。

不幸的是，这比它应该做的要多，因为c++没有“operator .”的重载。如果存在多态，则工作量更大。

但是这样做是值得的，因为这样您就不必担心内存泄漏，这意味着您甚至不需要寻找它们。

您可以使用Valgrind工具来检测内存泄漏。

此外，要找到特定函数中的漏洞，请在函数末尾使用exit(0)，然后使用Valgrind运行它

`$` valgrind ./your_CPP_program 

自动内存泄漏检查器的概述

在这个回答中，我在一个简单易懂的内存泄漏示例中比较了几种不同的内存泄漏检查程序。

在做任何事情之前，请参阅ASan wiki中比较人类已知所有工具的巨大表格:https://github.com/google/sanitizers/wiki/AddressSanitizerComparisonOfMemoryTools/d06210f759fec97066888e5f27c7e722832b0924

分析的例子如下:

c

#include <stdlib.h>

void * my_malloc(size_t n) {
    return malloc(n);
}

void leaky(size_t n, int do_leak) {
    void *p = my_malloc(n);
    if (!do_leak) {
        free(p);
    }
}

int main(void) {
    leaky(0x10, 0);
    leaky(0x10, 1);
    leaky(0x100, 0);
    leaky(0x100, 1);
    leaky(0x1000, 0);
    leaky(0x1000, 1);
}

GitHub上游。

我们将尝试看看不同的工具如何清楚地向我们指出泄漏的调用。

从gperftools通过谷歌

https://github.com/gperftools/gperftools

Ubuntu 19.04的用法:

sudo apt-get install google-perftools
gcc -ggdb3 -o main.out main.c -ltcmalloc
PPROF_PATH=/usr/bin/google-pprof \
  HEAPCHECK=normal \
  HEAPPROFILE=ble \
  ./main.out \
;
google-pprof main.out ble.0001.heap --text

程序运行的输出包含内存泄漏分析:

WARNING: Perftools heap leak checker is active -- Performance may suffer
Starting tracking the heap
Dumping heap profile to ble.0001.heap (Exiting, 4 kB in use)
Have memory regions w/o callers: might report false leaks
Leak check _main_ detected leaks of 272 bytes in 2 objects
The 2 largest leaks:
Using local file ./main.out.
Leak of 256 bytes in 1 objects allocated from:
        @ 555bf6e5815d my_malloc
        @ 555bf6e5817a leaky
        @ 555bf6e581d3 main
        @ 7f71e88c9b6b __libc_start_main
        @ 555bf6e5808a _start
Leak of 16 bytes in 1 objects allocated from:
        @ 555bf6e5815d my_malloc
        @ 555bf6e5817a leaky
        @ 555bf6e581b5 main
        @ 7f71e88c9b6b __libc_start_main
        @ 555bf6e5808a _start


If the preceding stack traces are not enough to find the leaks, try running THIS shell command:

pprof ./main.out "/tmp/main.out.24744._main_-end.heap" --inuse_objects --lines --heapcheck  --edgefraction=1e-10 --nodefraction=1e-10 --gv

If you are still puzzled about why the leaks are there, try rerunning this program with HEAP_CHECK_TEST_POINTER_ALIGNMENT=1 and/or with HEAP_CHECK_MAX_POINTER_OFFSET=-1
If the leak report occurs in a small fraction of runs, try running with TCMALLOC_MAX_FREE_QUEUE_SIZE of few hundred MB or with TCMALLOC_RECLAIM_MEMORY=false, it might help find leaks more re
Exiting with error code (instead of crashing) because of whole-program memory leaks

google-pprof的输出包含堆使用分析:

Using local file main.out.
Using local file ble.0001.heap.
Total: 0.0 MB
     0.0 100.0% 100.0%      0.0 100.0% my_malloc
     0.0   0.0% 100.0%      0.0 100.0% __libc_start_main
     0.0   0.0% 100.0%      0.0 100.0% _start
     0.0   0.0% 100.0%      0.0 100.0% leaky
     0.0   0.0% 100.0%      0.0 100.0% main

输出为我们指出了三个泄漏中的两个:

Leak of 256 bytes in 1 objects allocated from:
        @ 555bf6e5815d my_malloc
        @ 555bf6e5817a leaky
        @ 555bf6e581d3 main
        @ 7f71e88c9b6b __libc_start_main
        @ 555bf6e5808a _start
Leak of 16 bytes in 1 objects allocated from:
        @ 555bf6e5815d my_malloc
        @ 555bf6e5817a leaky
        @ 555bf6e581b5 main
        @ 7f71e88c9b6b __libc_start_main
        @ 555bf6e5808a _start

我不知道为什么第三个没出现

在任何情况下，通常当某些东西泄漏时，它会发生很多次，当我在一个真实的项目中使用它时，我只是很容易就被指出泄漏函数。

正如输出本身所提到的，这会导致显著的执行速度放缓。

进一步文件载于:

https://gperftools.github.io/gperftools/heap_checker.html https://gperftools.github.io/gperftools/heapprofile.html

参见:如何使用TCMalloc?

在Ubuntu 19.04中测试，google-perftools 2.5-2。

地址消毒(ASan)也由谷歌

https://github.com/google/sanitizers

前面提到过:如何在c++代码/项目中找到内存泄漏?TODO vs tcmalloc。

这已经集成到GCC中，所以你可以这样做:

gcc -fsanitize=address -ggdb3 -o main.out main.c
./main.out 

和执行输出:

=================================================================
==27223==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 4096 byte(s) in 1 object(s) allocated from:
    #0 0x7fabbefc5448 in malloc (/usr/lib/x86_64-linux-gnu/libasan.so.5+0x10c448)
    #1 0x55bf86c5f17c in my_malloc /home/ciro/test/main.c:4
    #2 0x55bf86c5f199 in leaky /home/ciro/test/main.c:8
    #3 0x55bf86c5f210 in main /home/ciro/test/main.c:20
    #4 0x7fabbecf4b6a in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x26b6a)

Direct leak of 256 byte(s) in 1 object(s) allocated from:
    #0 0x7fabbefc5448 in malloc (/usr/lib/x86_64-linux-gnu/libasan.so.5+0x10c448)
    #1 0x55bf86c5f17c in my_malloc /home/ciro/test/main.c:4
    #2 0x55bf86c5f199 in leaky /home/ciro/test/main.c:8
    #3 0x55bf86c5f1f2 in main /home/ciro/test/main.c:18
    #4 0x7fabbecf4b6a in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x26b6a)

Direct leak of 16 byte(s) in 1 object(s) allocated from:
    #0 0x7fabbefc5448 in malloc (/usr/lib/x86_64-linux-gnu/libasan.so.5+0x10c448)
    #1 0x55bf86c5f17c in my_malloc /home/ciro/test/main.c:4
    #2 0x55bf86c5f199 in leaky /home/ciro/test/main.c:8
    #3 0x55bf86c5f1d4 in main /home/ciro/test/main.c:16
    #4 0x7fabbecf4b6a in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x26b6a)

SUMMARY: AddressSanitizer: 4368 byte(s) leaked in 3 allocation(s).

它清楚地识别所有泄漏。好了!

ASan还可以做其他很酷的检查，比如越界写入:检测到堆栈破坏

在Ubuntu 19.04, GCC 8.3.0中测试。

Valgrind

http://www.valgrind.org/

之前提到过:https://stackoverflow.com/a/37661630/895245

用法:

sudo apt-get install valgrind
gcc -ggdb3 -o main.out main.c
valgrind --leak-check=yes ./main.out

输出:

==32178== Memcheck, a memory error detector
==32178== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==32178== Using Valgrind-3.14.0 and LibVEX; rerun with -h for copyright info
==32178== Command: ./main.out
==32178== 
==32178== 
==32178== HEAP SUMMARY:
==32178==     in use at exit: 4,368 bytes in 3 blocks
==32178==   total heap usage: 6 allocs, 3 frees, 8,736 bytes allocated
==32178== 
==32178== 16 bytes in 1 blocks are definitely lost in loss record 1 of 3
==32178==    at 0x483874F: malloc (in /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)
==32178==    by 0x10915C: my_malloc (main.c:4)
==32178==    by 0x109179: leaky (main.c:8)
==32178==    by 0x1091B4: main (main.c:16)
==32178== 
==32178== 256 bytes in 1 blocks are definitely lost in loss record 2 of 3
==32178==    at 0x483874F: malloc (in /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)
==32178==    by 0x10915C: my_malloc (main.c:4)
==32178==    by 0x109179: leaky (main.c:8)
==32178==    by 0x1091D2: main (main.c:18)
==32178== 
==32178== 4,096 bytes in 1 blocks are definitely lost in loss record 3 of 3
==32178==    at 0x483874F: malloc (in /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)
==32178==    by 0x10915C: my_malloc (main.c:4)
==32178==    by 0x109179: leaky (main.c:8)
==32178==    by 0x1091F0: main (main.c:20)
==32178== 
==32178== LEAK SUMMARY:
==32178==    definitely lost: 4,368 bytes in 3 blocks
==32178==    indirectly lost: 0 bytes in 0 blocks
==32178==      possibly lost: 0 bytes in 0 blocks
==32178==    still reachable: 0 bytes in 0 blocks
==32178==         suppressed: 0 bytes in 0 blocks
==32178== 
==32178== For counts of detected and suppressed errors, rerun with: -v
==32178== ERROR SUMMARY: 3 errors from 3 contexts (suppressed: 0 from 0)

所以再一次，所有的泄漏都被检测到了。

请参见:如何使用valgrind查找内存泄漏?

在Ubuntu 19.04, valgrind 3.14.0中测试。

确保成功释放了所有堆内存。如果您从未在堆上分配内存，则不需要这样做。如果你这样做，计算你malloc内存的次数，并计算你释放内存的次数。