c/c++：回调函数

1. 函数是一种function-to-pointer方式, 其会自动转换成指针的类型, &fun是该函数的地址, 为指针类型, fun是一个函数, 会转换成其指针类型, 而对于*fun, 由于fun已经变成了指针类型,

http://blog.csdn.net/callmeback/article/details/4242260/

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#include <stdio.h>
#include<iostream>
void printWelcome(int len)
{
	printf("欢迎欢迎 -- %d/n", len);
}

void printGoodbye(int len)
{
	printf("送客送客 -- %d/n", len);
}

void callback(int times, void(*print)(int))
{
	int i;
	for (i = 0; i < times; ++i)
	{
		print(i);
	}
	printf("/n我不知道你是迎客还是送客!/n/n");
}
void main(void)
{
	callback(10, printWelcome);


	std::cout << std::endl<< "--------------------------------------------------------------------------------------------" << std::endl;




	callback(10, printGoodbye);
	std::cout << std::endl << "--------------------------------------------------------------------------------------------" << std::endl;
	printWelcome(5);
}

1. 注册回调函数
   https://blog.csdn.net/mrailence/article/details/52251201

2. 回调函数demo

3. 回调函数demo2

4. 关于回调函数

名词解释

• LSB
  英文： Least Significant Bit
  中文： 最低有效位
  介绍： 对于一个给定的数据串（整数），如二进制的1001或者十进制351，其最低有效位就是拥有最小单位数值的那一位。比如二进制1001的最右一位，拥有数值1，在该整数中代表最低位，该位的值可以决定整数是奇数（为1）还是偶数（为0），十进制数同理。

一般LSB就是一个整数的最右一位，所以似乎该概念有些多余，==但是凡事都有例外，某些数据传输或是处理器恰恰相反，最左一位是LSB==，所以在计算领域就定义了这个最低有效位以明确说明数据格式。
注：相应的也有MSB - 最高有效位。

operator用法

示例:

• main.cpp

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  #include<iostream> #include"operator_test.h" using namespace std; MyInt::MyInt(int a, int b) { m_a = a; m_b=b; } void MyInt::operator -() { m_a = -m_a; m_b = -m_b; } void MyInt::print() { cout << "m_a=" << m_a << endl; cout << "m_b=" << m_b << endl; } int main() { MyInt F(14, -25); cout << "取负前:" << endl; F.print(); -F; //相当于: F.operator-(); cout << "取负后:" << endl; F.print(); }

• operator_test.h

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  class MyInt { private: int m_a; int m_b; public: MyInt(int a, int b); void operator - (); void print(); };

函数重载与定义

1. 函数重载示例

• mian.cpp

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  #include <stdio.h> #include<iostream> #include"overload.h" using namespace std; Tdate::Tdate() { month = 6; day = 20; year = 2002; cout << month << "/" << day << "/" << year << endl; } Tdate::Tdate(int m, int d) { month = m; day = d; year = 1979; cout << month << "/" << day << "/" << year << endl; } Tdate::Tdate(int m, int d, int y) { month = m; day = d; year = y; cout << month << "/" << day << "/" << year << endl; } void main() { Tdate adate; Tdate bdate(7, 2); Tdate cdate(4, 20, 2006); }

• overload.h

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  class Tdate { private: int month; int day; int year; public: Tdate(); Tdate(int m, int d); Tdate(int m, int d, int y); };

2. 函数再定义

• RefinitionFunction.h

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  #include<iostream> using namespace std; class Student { public: void display() { cout << "Student::display()" << endl; } }; class MiddleStudent :public Student { public: void display() { cout << "MiddleStudent::display()" << endl; } }; class GraduateStudent :public MiddleStudent { public: void display() { cout << "GraduateStudent::displayu()" << endl;} };

• main.cpp

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  #include <stdio.h> #include<iostream> #include"RefinitionFunction.h" using namespace std; void main() { Student s; MiddleStudent ms; GraduateStudent gs; s.display(); ms.display(); gs.display(); cout << "------------------------------" << endl; Student *ps; ps = &s; ps->display(); ps = &ms; ps->display(); ps = &gs; ps->display(); cout << "------------------------------" << endl; MiddleStudent *take; take = &ms; take->display(); }

【OutPut】

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Student::display()
MiddleStudent::display()
GraduateStudent::displayu()
------------------------------
Student::display()
Student::display()
Student::display()
------------------------------
MiddleStudent::display()
Press any key to continue . . .

ADO编程实用宝典
ADO技术简介(完全攻略)

1. This function or variable may be unsafe
   vs2015报错:

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   Severity Code Description Project File Line Suppression State Error C4996 'sprintf': This function or variable may be unsafe. Consider using sprintf_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details. DLL_ZBLCommunication d:\gx_2017\2017-07\0\dll_zblcommunication\dll_zblcommunication\zblcommunication.cpp 156 Severity Code Description Project File Line Suppression State Error C4996 'fopen': This function or variable may be unsafe. Consider using fopen_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details. DLL_ZBLCommunication d:\gx_2017\2017-07\0\dll_zblcommunication\dll_zblcommunication\zblcommunication.cpp 504 Severity Code Description Project File Line Suppression State Error C4996 'fopen': This function or variable may be unsafe. Consider using fopen_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details. DLL_ZBLCommunication d:\gx_2017\2017-07\0\dll_zblcommunication\dll_zblcommunication\zblcommunication.cpp 531

解决:

1. 工程属性添加预处理命令
   在属性页面中找到“C/C++”——”预处理器“，按下图操作单击箭头指向处的按钮

在下面的编辑窗口中添加一句命令：_CRT_SECURE_NO_WARNINGS
添加完成后应用并退出

2. 我在代码开头添加

   1	#define _CRT_SECURE_NO_WARNINGS

2. unexpected token(s) preceding;'、type 'int' unexpected、this declaration has no storage class or type specifer

解决:在出错代码前加

1

#include<Windows.h>

3. ‘<<’没有找到std::string重装数

   1	Error 1 error C2679: binary '<<' : no operator found which takes a right-hand operand of type 'std::string' (or there is no acceptable conversion) g:\vs_project\vs_2013\consolewein32_vs2013\consolewein32_vs2013\vs2013_main.cpp 20 1 consolewein32_VS2013

   解决办法:
   加上头文件#include<string>

4. ntelliSense: no default constructor exists for class “Base”

报错代码:
C++

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 #include <iostream>
using namespace std;

class Base
{
private:
	int n;

public:
	Base(int m) :n(m){ cout << "constructor is called\n"; }
	~Base(){}
};

class Derive :public Base
{
private:
	int n;

public:
	Derive(int m) :n(m)
	{
		Base(3);
	}
	~Derive(){}
};

int main()
{
	Derive* a = new Derive(10); return 0;
}

解决：

1. 两个类有继关系,父类没有显示声明无参构造数,但声明了有参数构函数，必须用参数列列表初始化;
   参照文章:C++中必须用参数列表初始化的4种情况

2. 在基类里添加无参数构造函数;

• 在xp+vs2005使用 Winbase.h头文件报错:

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  CGxmisCommunication.cpp c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(226) : error C2146: syntax error : missing ';' before identifier 'Internal' c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(226) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(226) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(227) : error C2146: syntax error : missing ';' before identifier 'InternalHigh' c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(227) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(227) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(230) : error C2146: syntax error : missing ';' before identifier 'Offset' c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(230) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(230) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(231) : error C2146: syntax error : missing ';' before identifier 'OffsetHigh' c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(231) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(231) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(234) : error C2146: syntax error : missing ';' before identifier 'Pointer' c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(234) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(234) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(237) : error C2146: syntax error : missing ';' before identifier 'hEvent' c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(237) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(237) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(241) : error C2146: syntax error : missing ';' before identifier 'nLength' c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(241) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(241) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(242) : error C2146: syntax error : missing ';' before identifier 'lpSecurityDescriptor' c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(242) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(242) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(243) : error C2146: syntax error : missing ';' before identifier 'bInheritHandle' c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(243) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(243) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(247) : error C2146: syntax error : missing ';' before identifier 'hProcess' c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(247) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(247) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(248) : error C2146: syntax error : missing ';' before identifier 'hThread' c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(248) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(248) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(249) : error C2146: syntax error : missing ';' before identifier 'dwProcessId' c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(249) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(249) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(250) : error C2146: syntax error : missing ';' before identifier 'dwThreadId' c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(250) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(250) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(261) : error C2146: syntax error : missing ';' before identifier 'dwLowDateTime' c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(261) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(261) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(262) : error C2146: syntax error : missing ';' before identifier 'dwHighDateTime' c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(262) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(262) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(272) : error C2146: syntax error : missing ';' before identifier 'wYear' c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(272) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(272) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(273) : error C2146: syntax error : missing ';' before identifier 'wMonth' c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(273) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(273) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(274) : error C2146: syntax error : missing ';' before identifier 'wDayOfWeek' c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(274) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(274) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(275) : error C2146: syntax error : missing ';' before identifier 'wDay' c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(275) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(275) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(276) : error C2146: syntax error : missing ';' before identifier 'wHour' c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(276) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(276) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(277) : error C2146: syntax error : missing ';' before identifier 'wMinute' c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(277) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(277) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(278) : error C2146: syntax error : missing ';' before identifier 'wSecond' c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(278) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(278) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(279) : error C2146: syntax error : missing ';' before identifier 'wMilliseconds' c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(279) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(279) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(283) : error C2065: 'WINAPI' : undeclared identifier c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(283) : error C2065: 'PTHREAD_START_ROUTINE' : undeclared identifier c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(283) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 8\vc\platformsdk\include\winbase.h(283) : fatal error C1903: unable to recover from previous error(s); stopping compilation Generating Code... Compiling... Serial.cpp

  解决:
  不能直接使用#include <Winbase.h>

应该改为#include <Windows.h>

• Error C1083 Cannot open include file: ‘windows.h’: No such file or directory
  出错环境 win10+vs2015+Berkeley DB XML 6.0.18

实际解决:

把工程属性中VC++ Directories中选项:Library Directories、Include Diretories设置Berkeley DB XML 6.0.18相应路径

• C1073: Internal error involving incremental compilation

Severity Code Description Project File Line Suppression State
Error C1073 Internal error involving incremental compilation(compiler file ‘f:\dd\vctools\compiler\cxxfe\sl\p1\c\p0io.c’, line 997) UnitTest d:\github\crcpp\inc\crc.h 1

解决:
工程属性—> Configuration Properties——>C/C++——–>Code Generation—–>Enable Minimal Rebuild :No(/Gm-)

• error LNK2005: _DllMain@12 already defined

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  LINK : warning LNK4076: invalid incremental status file 'C:\DLL_TVM_ZZ14A\TVM_Driver_ZZ14A\Debug\ZZ14AGeneralControlTVM.ilk'; linking nonincrementally mfcs80ud.lib(dllmodul.obj) : error LNK2005: _DllMain@12 already defined in ZZ14AGeneralControlTVM.obj Creating library C:\DLL_TVM_ZZ14A\TVM_Driver_ZZ14A\Debug\ZZ14AGeneralControlTVM.lib and object C:\DLL_TVM_ZZ14A\TVM_Driver_ZZ14A\Debug\ZZ14AGeneralControlTVM.exp C:\DLL_TVM_ZZ14A\TVM_Driver_ZZ14A\Debug\ZZ14AGeneralControlTVM.dll : fatal error LNK1169: one or more multiply defined symbols found

  解决办法:
  创建MFC的DLL工程时，预处理器使用了_USRDLL选项，其意思是说：在DLL连接MFC库的时候使用静态连接的方式。而本身MFC的库中带有_DllMain函数的定义，造成重定义。

Configuration Properties—>C/C++—–>Preprocessor:—->Preprocessor Definitions:去掉_USRDLL 选项

• Compiler Error C2065

如果在源码文件里有声明了变量，但是却总是报错 ‘identifier’:undeclared identifier,首先检查文件编码格式问题

Compiler Error C2065

vs2005使用Berkeley DB XML 2.3.10编程的时候报连接错误

在使用C++编程的时候连接问题

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main.obj : error LNK2019: unresolved external symbol "public: __thiscall Dbt::~Dbt(void)" (??1Dbt@@QAE@XZ) referenced in function _main
main.obj : error LNK2019: unresolved external symbol "public: __thiscall Dbt::Dbt(void)" (??0Dbt@@QAE@XZ) referenced in function _main

工程属性设置：
Configuration Properties—>C/C++填上:
C:\Program Files\Oracle\Berkeley DB XML 2.3.10\include

Configuration Properties—>Linker—> Input 填上: libdb45d.lib

参考文章
http://www.91linux.com/Berkeley_DB/2014/0131/5719.html

2. 找不到“kernel32.lib”

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   警告 1 warning MSB8003: Could not find WindowsSDKDir variable from the registry. TargetFrameworkVersion or PlatformToolset may be set to an invalid version number. C:\Program Files\MSBuild\Microsoft.Cpp\v4.0\V120\Microsoft.CppBuild.targets 355 5 test 错误 2 error LNK1104: 无法打开文件“kernel32.lib” c:\Users\vm_win7x86\documents\visual studio 2013\Projects\test\test\LINK test

   更改项目属性为 XP

boost配置报错

1. LNK1104

   1	1>LINK : fatal error LNK1104: cannot open file 'libboost_thread-vc100-mt-gd-1_57.lib

原因:
boost库编译时用的link=shared runtime-link=shared threading=multi，所以生成的是 boost_thread-vc100-mt-gd-1_57.dll和导出库 boost_thread-vc100-mt-gd-1_57.lib。

解决办法:
project –> Property—-> Configuration Properties—>C/C++—->Preprocessor–(右边选项卡)——>Preprocessor Definitions—(添加)—->BOOST_ALL_DYN_LINK

参考[C/C++]使用boost时无法连接到正确的库，提示fatal error LNK1104

2. boost程序运行报错找不到动态库

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The code execution cannot proceed because boost_thread-vc100-mt-gd-1_57.dll was not found.Reinstalling the  program may fix this  problem.

同样报错的还有：
+ boost_date_time-vc100-mt-gd-1_57.dll

+ boost_system-vc100-mt-gd-1_57.dll

解决:
把缺失的dll， 放入程序运行目录下即可解决