Use of static library and dynamic library

First, let's introduce the static library （ Static link library ）、 Dynamic library （ Dynamic link library ） The concept of , First of all, both are ways of code sharing .

Static library ： In the link step , The connector will get the required code from the library file , Copy to the generated executable file , This library is called a static library , Its characteristic is that the executable file contains a complete copy of the library code ; The disadvantage is that if it is used many times, there will be multiple redundant copies . That is, all the instructions in the static library are directly included in the final generated EXE It's in the document . stay vs Create a new project to generate a static library in , After successful compilation and generation , Only one .lib file

Dynamic library ： Dynamic link library is a library that contains code and data that can be used by multiple programs at the same time ,DLL It's not an executable file . Dynamic linking provides a way , Enables a process to call functions that are not part of its executable code . The executable code of the function is in a DLL in , The DLL Contains one or more compiled 、 Functions linked and stored separately from the processes that use them . stay vs Create a new project to generate dynamic library in , After successful compilation , Produce a .lib Documents and a .dll file , Creating a dynamic library requires

__declspec(dllexport) As a prefix to a function ：__declspec(dllexport) void test1();

Then the static library and the dynamic library lib What's the difference ？

In a static library lib： The LIB Contains the function code itself （ That is, including the index of the function , It also includes the implementation of ）, Add code directly to the program at compile time

In dynamic library lib： The LIB Contains the... Where the function is located DLL File and function location information in the file （ Indexes ）, The function implementation code is loaded in the process space by the runtime DLL Provide

All in all ,lib It's used when compiling ,dll It's used at runtime . If you want to compile the source code , It only needs lib; If you want to make the dynamic link program run , It only needs dll.

 

Call dynamic library ： Implicit linking

Implicit linking need .h file ,dll file ,lib file

（1） take dll Put it into the working directory of the project

（2） Set item properties --vc++ Catalog -- The library directory is lib Path

（3） take lib Add to project properties -- The linker -- Input -- Additional dependency （ Or add... Directly to the source code #pragma comment(lib, “**.lib”)）

（4） Add... To the source file .h The header file

Then call ordinary functions as usual 、 class 、 Variable

Use static libraries

need .h file ,lib file

（1） Set item properties --vc++ Catalog -- The library directory is lib Path

（2） take lib Add to project properties -- The linker -- Input -- Additional dependency （ Or add... Directly to the source code #pragma comment(lib, “**.lib”)）

（3） Add... To the source file .h The header file