- How to create makefile for c program in linux install#
- How to create makefile for c program in linux driver#
- How to create makefile for c program in linux software#
- How to create makefile for c program in linux code#
$ export LD_LIBRARY_PATH=/home/username/foo:$LD_LIBRARY_PATH The loader and our test program did not inherit the changes we made. In Linux, if you do not export the changes to an environment variable, they will not be inherited by the child processes. What happened? Our directory is in LD_LIBRARY_PATH, but we did not export it. $ LD_LIBRARY_PATH=/home/username/foo:$LD_LIBRARY_PATH Let us fix that by prepending our working directory to the existing LD_LIBRARY_PATH: Let us take a look first at LD_LIBRARY_PATH: Using LD_LIBRARY_PATH We have a couple of options: we can use the environment variable LD_LIBRARY_PATH for this, or rpath.
How to create makefile for c program in linux install#
3 We did not install it in a standard location, so we need to give the loader a little help. Oh no! The loader cannot find the shared library. test: error while loading shared libraries: libfoo.so: cannot open shared object file: No such file or directory Step 4: Making the library available at runtime $ gcc -L/home/username/foo -Wall -o test main.c -lfoo In this example, we will use the current directory, /home/username/foo: 2 We need to tell GCC where to find libfoo.so. GCC has a list of places it looks by default, but our directory is not in that list. Uh-oh! The linker does not know where to find libfoo. Telling GCC where to find the shared library a is for archive, or statically linked libraries). a (.so is for shared object or shared libraries, and. GCC assumes that all libraries start with lib and end with. Note that the -lfoo option is not looking for foo.o, but libfoo.so. Let us compile our main.c and link it with libfoo. We will call it libfoo.so:Īs you can see, that was actually pretty easy. Now we need to actually turn this object file into a shared library. Step 2: Creating a shared library from an object file
How to create makefile for c program in linux code#
We need to compile our library source code into position-independent code (PIC): 1
How to create makefile for c program in linux driver#
foo.c contains the implementation of that function, and main.c is a driver program that uses our library.įor the purposes of this example, everything will happen in /home/username/foo Step 1: Compiling with Position Independent Code Puts("This is a shared library test.") įoo.h defines the interface to our library, a single function, foo(). Steps 3 and 4 are where the magic (and confusion) happens with shared libraries. Any references found are resolved and the libraries are mapped into your program. Your program is scanned for references to shared libraries.
How to create makefile for c program in linux software#
Most larger software projects will contain several components, some of which you may find use for later on in some other project, or that you just want to separate out for organizational purposes. They often provide generic functionality, like linked lists or binary trees that can hold any data, or specific functionality like an interface to a database server such as MySQL. They are pre-existing code that is compiled and ready for you to use. Libraries are an indispensable tool for any programmer.