CODEWITHSUNDEEP
c++g++dynamic-linkingld
lazlow
lazlow

Reputation: 73

Why doesn't g++ link with the dynamic library I create?

I've been trying to make some applications which all rely on the same library, and dynamic libraries were my first thought: So I began writing the "Library":

/* ThinFS.h */

class FileSystem {
public:
    static void create_container(string file_name); //Creates a new container 
};

/* ThinFS.cpp */
#include "ThinFS.h"
void FileSystem::create_container(string file_name) {
     cout<<"Seems like I am going to create a new file called "<<file_name.c_str()<<endl;
}

I then compile the "Library"

g++ -shared -fPIC FileSystem.cpp -o ThinFS.o

I then quickly wrote a file that uses the Library:

#include "ThinFS.h"
int main() {
    FileSystem::create_container("foo");
    return (42);
}

I then tried to compile that with

g++ main.cpp -L. -lThinFS

But it won't compile with the following error:

/usr/bin/ld: cannot find -lThinFS
collect2: ld returned 1 exit status

I think I'm missing something very obvious, please help me :)

Upvotes: 7

Views: 26312

Answers (5)

jernkuan
jernkuan

Reputation: 630

You can use 

g++ main.cpp -L. -l:ThinFS

The use of "colon" will use the library name as it is, rather requiring a prefix of "lib"

Upvotes: 6

Hardy
Hardy

Reputation: 222

Check out this article.

http://www.yolinux.com/TUTORIALS/LibraryArchives-StaticAndDynamic.html

A good resource on how to build different types of libraries. It also describes how and where to use them.

Upvotes: 0

Chris Dodd
Chris Dodd

Reputation: 2960

-lfoo looks for a library called libfoo.a (static) or libfoo.so (shared) in the current library path, so to create the library, you need to use g++ -shared -fPIC FileSystem.cpp -o libThinFS.so

Upvotes: 13

Luk&#225;š Lalinsk&#253;
Luk&#225;š Lalinsk&#253;

Reputation: 41316

The result of g++ -shared -fPIC FileSystem.cpp is not an object file, so it should not end with .o. Also, shared libraries should be named libXXX.so. Rename the library and it will work.

Upvotes: 2

anon
anon

Reputation:

the name of the output file should be libThinFS.so, e.g.

g++ -shared -fPIC FileSystem.cpp -o libThinFS.so

Upvotes: 3

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