Why LD_LIBRARY_PATH is BAD and the correct way to load dynamic libraries

Question

So, I have a program that runs with OpenBlas and I want to compile it. The linking process looks like this:

gcc -o prog prog.o -O3 -I/opt/OpenBLAS/include -L/opt         


        

Answer 1

On linux, it is also possible to use $ORIGIN in rpath to mean the directory path to the application and build a relative rpath from there. You would then move the library to a known relative path to the binary.

gcc -o prog prog.o -O3 -I/opt/OpenBLAS/include -Wl,-rpath=\$ORIGIN/lib -L/opt/OpenBLAS/lib -lopenblas

You can also use the full path to the libary, and it will be linked in:

gcc -o prog prog.o -O3 -I/opt/OpenBLAS/include /opt/OpenBLAS/lib/libopenblas.so

If you run "ldd" on the executable, you should see the full path encoded.

Answer 2

Add the path to the runtime library search path.

gcc -Wl,-rpath=/opt/OpenBlas/lib ...

What the -L option does at link time, the -rpath option does at run time.