LP Devs Blog

Build static library cpp in Ubuntu

Posted on February 09, 2017

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Library is very important when you build some kind of big systems. Some advantages of library are:

• You have to write less code
• Easy to fix code
• Easy to share to others
• …

In this post, I am going to share one way to build static library in Ubuntu. First of all, you can get source files on Github.

Structure of project

• test
  • main.cc
  • Makefile
• lib.h
• lib.cc
• Makefile

Detail

• lib.h:

  #ifndef _LIB_H_
  #define _LIB_H_
    void sayHi();
  #endif
  

• lib.cc:

  #include "lib.h"
  #include <stdio.h>
  void sayHi()
  {
    printf("Hello from static library\n");
  }
  

• Makefile:

  CC = g++
  libmylib.a: lib.o
      ar rcs $@ $^
  lib.o: lib.cc lib.h
      $(CC) -c -o $@ $<
  clean:
      rm -f *.o *.a
  

  • Compiler: g++
  • Output: libmylib.a
  • $@: means target
  • $^: all dependencies
  • $<: first dependency
  • “ar rcs …” is to build static library.
• test/main.cc

  #include "../lib.h"
  #include <stdio.h>
  int main()
  {
    sayHi();
    return 0;
  }
  

• test/Makefile

  TARGET = prog
  CC = g++
  LDFLAGS = -L..
  LIBS = -static -lmylib
  $(TARGET): main.o 
    $(CC) $^ $(LDFLAGS) $(LIBS) -o $@
  main.o: main.cc 
    $(CC) -c $^ -o $@ 
  clean: rm -f *.o $(TARGET)
  

  • LDFLAGS: directory of library (libmylib.a) with option -L
  • LIBS: name of library (mylib) with option -l (without prefix “lib” and suffix “.a”)

Building static library

• Assuming that you are in /build-static-library-cpp-ubuntu directory.

  make
  

Testing static library

• Run:

  cd test
  make
  ./prog
  

• Result should be: Hello from static library

Thanks for reading. If you have some questions, feel free to ask me.
LP Devs

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Categories: Cpp | Ubuntu
Tags: Static library | Makefile