CODEWITHSUNDEEP
c++linker
lknfdhu
lknfdhu

Reputation: 489

How can I add a (.a) static library to a C++ program?

How can I use a static library in a C++ program that I have created?

For example, lets say I preform the following actions:

1. First I create file: foo.h, and add the following code:

  int foo(int a);

2. In turn I create foo.cpp, and I add the following:


  #include foo.h

  int foo(int a)
  {
    return a+1;
  }

3. Then I use GNU's C++ compiler GCC (except I use the G++ version) which looks something like the following:

3a.   g++ foo.cpp
3b.   ar rc libfoo.a foo.o


4. I create my program's main file, main.cpp

File: "main.cpp"

#include "foo.h"

int main()
{ 
    int i = foo(2);
    return i;
}

Here is where I am getting an error. How can I compile my .a static library with main.cpp?

What I am attempting to do is the following:

g++ -L. -lfoo prog.cpp

but get an error because the function foo would not be found

Upvotes: 17

Views: 31961

Answers (1)

user2100815
user2100815

Reputation:

You want:

g++ -L.  prog.cpp -lfoo

Unfortunately, the ld linker is sensitive to the order of libraries. When trying to satisfy undefined symbols in prog.cpp, it will only look at libraries that appear AFTER prog.cpp on the command line.

You can also just specify the library (with a path if necessary) on the command line, and forget about the -L flag:

g++ prog.cpp libfoo.a

Upvotes: 21

Related Questions