我是Windows平台上的c++程序员。我使用的是Visual Studio 2008。

我通常会在代码中出现内存泄漏。

通常我通过检查代码来发现内存泄漏,但这很麻烦,而且并不总是一种好方法。

因为我买不起付费的内存泄漏检测工具,所以我想让你们建议避免内存泄漏的最佳方法。

我想知道如何程序员可以找到内存泄漏。 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?


当前回答

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).

其他回答

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。

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.

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。

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.

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)。