How can I add libdl to to a waf build?

Question

I'm trying to call the dlsym function from a program compiled with the waf build system, but am unable to link libdl using the wscript. This SEEMS like an extremely simple task but I've tried a million different things and have gotten nowhere.

Edit: It would be even better if there were a general way to add flags to the end of each build command. I've tried setting CXXFLAGS and other environment variables but they don't seem to change anything...

Answer 1

If you try to pass use=dl to the build command directly, waf will look in the config environment dict for "uselib variables" to tell it how to handle it.

A minimal wscript to build a simple test.c program with dl might look like this:

def options(opt):
    opt.load('compiler_c')

def configure(conf):
    conf.load('compiler_c')

    # Make sure the we're able to link against dl
    conf.check(lib='dl')

    # If someone passes LIB_DL, to the build command, link against system library dl
    conf.env.LIB_DL = 'dl'

def build(bld):
    bld(source='test.c',
        target='test_program',
        features='c cprogram',

        # Waf will look in LIB_DL, LIBPATH_DL, CXXFLAGS_DL, etc. for how to handle this
        use='DL')

Relevant documentation

Waf also provides a shorthand to avoid having to explicitly set LIB_DL:

def configure(conf):
    conf.load('compiler_c')
    conf.check(lib='dl', uselib_store='DL')     

This is somewhat documented here

For the sake of completeness, here's the test.c file I used to test:

#include <dlfcn.h>

int main(int argc, char** argv)
{
    dlopen("some/file", RTLD_LAZY);
    return 0;
}