GNU ld cannot find library which is there

Question

The packages I'm toying with here are rather unknown, but nevertheless the problem is rather generic. Basically, I'm trying to compile Python module (called rql) with C++ extension. The extension uses external framework called gecode, which contains several libraries. I compiled gecode and installed locally. Now, let the output speak for itself:

red@devel:~/build/rql-0.23.3$ echo $LD_LIBRARY_PATH
/home/red/usr/lib
red@devel:~/build/rql-0.23.3$ ls $LD_LIBRARY_PATH | grep libgecodeint 
libgecodeint.so
libgecodeint.so.22
libgecodeint.so.22.0
red@devel:~/build/rql-0.23.3$ python setup.py build
running build
running build.py
package init file './test/__init__.py' not found (or not a regular file)
running build_ext
building 'rql_solve' extension
g++ -pthread -shared build/temp.linux-i686-2.5/gecode-solver.o -lgecodeint -lgecodekernel -lgecodesearch -o build/lib.linux-i686-2.5/rql_solve.so
/usr/bin/ld: cannot find -lgecodeint
collect2: ld returned 1 exit status
error: command 'g++' failed with exit status 1

Gainsborough

Is LD_LIBRARY_PATH exported in your environment? – Subvert

Is the libgecodeint.so that is in your LD_LIBRARY_PATH for the right architecture (e.g. 32-bit or 64-bit as appropriate)? – Slumlord

Answer 1

LD_LIBRARY_PATH is for runtime linker/loader (same effect could be achieved with ldconfig ). What you need is the -L flag:

-L/home/red/usr/lib

on the compiler command line.

Edit:

And - thanks to @bjg for reminding me - you can use LIBRARY_PATH if you don't want to mess with compiler options.

Sabrina

Yes, I would mark his comment as answer if I could :) It's kinda strange that ld doesn't look in it's runtime search path anyway, but the problem is solved now, so big thanks to you and others here! – Gainsborough

Answer 2

You've apparently modified LD_LIBRARY_PATH to point to a non-standard location in your home directory. Do you know if LD_LIBRARY_PATH in the environment used to call g++ in setup.py matches your shell's environment?

See if you can pass arguments to setup.py to modify the library path or simply pass -L/home/red/usr/lib to g++.

Devout

g++ will use LIBRARY_PATH if present so you could try LIBRARY_PATH=/red/usr/lib python setup.py build – Subvert