Building an NPAPI browser plugin on Linux x86 and x86_64, how do I ensure that it loads the correct version of its dependent libraries?

Question

I'm attempting to build a Linux browser plugin using Firebreath that runs on 32bit and 64bit Linux.

In my X11/projectDef.cmake I have

target_link_libraries(${PROJECT_NAME}
    ${PLUGIN_INTERNAL_DEPS}
    "${CMAKE_CURRENT_SOURCE_DIR}/lib/libOIS-1.4.0_32.so"
    )

Currently I'm just manually changing that line switching 32 to 64 when I want to do a different build, so that's probably wrong. But my issue is that even when I build with the 32bit library and it compiles successfully, I get the following error when trying to load the plugin in Firefox:

$ firefox
LoadPlugin: failed to initialize shared library /home/daniel/.mozilla/plugins/npBoomstickJavaScriptJoystickSupport.so [libOIS-1.4.0.so: wrong ELF class: ELFCLASS64]

How do I set up my cmake to automatically include the correct library depending on the architecture? Is there a way to build both x86 and x86_64 simultaneously on the same machine? How do I get the plugin to load correctly or is there a way to further debug this problem?

Answer 1

As far as I know the only way to do a build for 32 bit on a 64 bit machine is to use cross compiling: http://www.vtk.org/Wiki/CMake_Cross_Compiling

I've never actually tried this, but inside CMake you can probably use the CMAKE_SIZEOF_VOID_P which will be 4 in 32 bit mode, 8 in 64 bit. You could add an if to your cmake script to set the correct binaries depending on the size of that.