C++ | Knight.Liao's Tale

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标签： C++

Pointer Bad Usage Example: Memory Leak!

三 30

When we use C++ pointer, we should save the pointer and the original pointer should not be thrown away in our program.

A bad usage example about C++ pointer is :

	int *a = new int;
	*a = 2;
	int b = *a;
	delete &b;

We have a pointer "a", we assign its value to object "b" and we throw away the pointer "a". And we delete object "b" when we want to release the memory what pointer "a" has allocated.

However, we will meet "Memory Leak" error when we want to release(delete) object "b",( we want to release pointer "a" , but this pointer is lost. We will release object "b" because pointer is assigned to object "b".)

Another wrong usage example is :

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我要发言 C++, Memory Leak, pointer 阅读全文

Name of "Struct" and "function" can be the same

一 6

C++

when I read the code ( From book "Beginning Linux Programming 4th Edition" )

int stat(const char *path, struct stat *buf);

I found that this function name "stat" is equal to the struct name "stat". First, I feel a little surprised. How the struct name can be equal to the name of function? Why the G++(GCC) compiler doesn't throw out complains?

Then I tried the following codes which are written by me:

struct statExample
{

};

void statExample(struct statExample *buf=NULL)
{
	printf("Nothing\n");
}

void main()
{
	struct statExample x;
	statExample(&x);
}

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我要发言 C++, equal, function name, same, struct name 阅读全文

关于栈、堆、静态存储区最大可分配大小的探讨

九 2

C++

中午看《编程之美》的第2.5节中有这么一小段程序：

float array[100 000 000];

这个1亿个float变量，这样就有8亿个字节，转化为二进制单位G，就是小于等于1G。这样大小的数组量只能用堆（动态申请内存变量）或者静态存储区（全局变量）来申请。

好了，转入今天要讲的正题。到底栈、堆、静态存储区能申请的最大分配大小是多少呢？

栈(stack)

栈大小与编译器有关。

默认情况下，visual studio 2010 的栈大小为1M。但在平时应用程序中，由于函数会使用栈结果，所以只能用略小于1M大小的栈。
对于64位和32位程序，结果都是一样的，因为VS2010已经设定好了默认的栈大小了。

	const int nStackSize = 249036; // 这是0.95M
	int b[nStackSize];

	for(int i=0;i< nStackSize;++i)
		b[i] =0;

	std::cout << b[nStackSize-1];

静态存储区(全局变量）

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3 条评论 C++, SuperLu, 全局变量, 内存, 堆, 大小, 栈, 编程之美 阅读全文

Strategy Design Pattern (C++)

七 15

Design Pattern

This is a C++ project that describe the usage of Strategy Pattern design
The aim is to implement one task which is in the page 25 of <Head First> ( Chinese version ).

creatd by Knight 2010.07.15
www.liaoqiqi.com/blog

Full Codes:

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我要发言 C++, Design Pattern, Strategy Pattern 阅读全文

Builder Design Pattern and Decorator Design Pattern (C++)

七 14

Design Pattern

This is a C++ project that describe the usage of Builder Pattern design and Decorator Pattern design.
The aim is to implement one task which is in the page 614 of <Head First> ( Chinese version ).

File List:

Vocation.h : Implement Decorator Pattern design
Vocation.cpp : Implement Decorator Pattern design
Builder.h : Implement Builder Pattern design
Builder.cpp : Implement Builder Pattern design
Test.cpp : a test driver

There are several important tips:
1. Java have memory garbage, but C++ don't have. So you should be careful when you use Decorator Pattern design.
The trick is that you should write destructor for every decorator class. ( ex, VocationHotel, VocationTicket )

creatd by Knight 2010.07.14
www.liaoqiqi.com/blog

UML Chart：

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我要发言 Builder Pattern, C++, Decorator Pattern, Design Pattern 阅读全文

Some bad C++ programming habits which may lead to Memory Leak Error

六 7

C++

There are some bad programming habits in my experience which can lead to Memory Leak:

Use inherit class structure. But you never writing virtual destructions method for your base class.
use "new" to create one object, but forgetting to write "delete" statement for this object. ( This bad codes can be detected by some tricks: http://www.liaoqiqi.com/blog/2010/06/01/how-to-make-memory-leak-detection-in-c/comment-page-1/#comment-218 )
create an array objects, but use "delete" instead of " delete []" to destory the array objects.

To be continued....

我要发言 C++, habit, Memory Leak, programming 阅读全文

Non-Memory Leak version Singleton pattern implementation with C++

六 3

Design Pattern

I wrote a single pattern with C++ implementation[1] article the day before yesterday. However, this version has one fatal problem: it has Memory Leak error! This is because you use "new" to malloc memory explicitly, but you never delete it manually. Although OS will help you free this heap, you program reallly exist memory leak problem.

It's well known that Java has garbage collector, so he never thinks of freeing the memory. But we are C++ programmers, we should free heap memory if we new/malloc them.

Ok, Now I'll introduce my C++ single pattern correct version:
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2 条评论 C++, Non-Memory Leak, Singleton pattern 阅读全文

Never call virtual functions during construction

六 2

C++

I read <Effective C++> at one time, and I know there is a criterion which is "Never call virtual functions during construction and destruction". But as we all know, genuine knowledge comes from practice. We will never have in-depth understanding of knowledge unless we touch them by ourselves.

Today I want to write a class with Factory patterns in C++.

class DemoModelClass
{
public :
    // common functions
    DemoModelClass()
    {
        CreateDemoModelResourceFactory();   // 1st problem!
        CreateOtherData();
    }    

private:
    virtual void CreateDemoModelResourceFactory()=0{};   // 2nd problem!
    void CreateOtherData(){.....};
}

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2 条评论 C++, Design Pattern, destruction, Factory, functions, virtual 阅读全文

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Knight.Liao's Tale

存档

Pointer Bad Usage Example: Memory Leak!

Name of "Struct" and "function" can be the same

关于栈、堆、静态存储区最大可分配大小的探讨

栈(stack)

静态存储区(全局变量）

Strategy Design Pattern (C++)

Full Codes:

Builder Design Pattern and Decorator Design Pattern (C++)

UML Chart：

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Some bad C++ programming habits which may lead to Memory Leak Error

Non-Memory Leak version Singleton pattern implementation with C++

Never call virtual functions during construction

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