Dynamic library invocation static library example

Generate dynamic libraries: the required target files are generated using the -fPIC option.

The target files required for the static library can be used without the -fPIC option.

Ex. :

/////// static.h
void static_print();
///////static.cpp
#include <iostream>
#include "static.h"
void static_print() {
     std::cout<<"This is static_print function"<<std::endl;
}
////// shared.h
void shared_print();
////// shared.cpp
#include <iostream>
#include "shared.h"
#include "static.h"
void shared_print() {
       std::cout<<"This is shared_print function";
        static_print();
}
////////test.cpp
   #include "share.h"

int main()
{
       shared_print();
       return 0;
   }

Method 1:

The.o file for the static library is also generated with -fPIC. Add the static library to the dynamic library.

  loads only dynamic libraries when it generates applications

 g++ -c -fPIC static.cpp //  generate static.o
 ar -r libstatic.a static.o //  Generate static library libstatic.a
 g++ -c -fPIC shared.cpp //  generate shared.o
 g++ -shared shared.o -lstatic -o libshared.so   //  Generate dynamic library libshared.so  note : -shared is g++ The option to , with shared.o Has nothing to do . -lstatic The options libstatic.a Is added to the dynamic library .
 g++ test.cpp -lshared -o test.exe // link libshared.so  to test.exe In the .
 

Method 2:

  static library.o file is not generated by -fPIC.

Dynamic and static libraries are loaded when the application is generated.

 g++ -c static.cpp //  generate static.o
 ar -r libstatic.a static.o //  Generate static library libstatic.a
 g++ -c -fPIC shared.cpp //  generate shared.o
 g++ -shared shared.o -o libshared.so //  Generate dynamic library libshared.so  note : -shared is g++ The option to , with shared.o Has nothing to do .  So if I add -lstatic. error:relocation R_X86_64_32 against `a local symbol' can not be used when making a shared object; recompile with -fPIC
 g++ test.cpp -lshared -lstatic -o test.exe // link libshared.so  to test.exe In the .
 

The difference between the two methods is that the actual code for static_print is 1 in.so and 1 in the final test.exe file.