Including libtld from a native addon in nodejs

[betomoretti]

Hi all!

I'm playing around with this library trying to use it from a node addon but I couldn't do it. I don't have experience with C++ and I know that it sounds like weird. But I really want to make some experiments running this library from nodejs. To do it, I'm trying to implement an addon that brings some bindings between JavaScript and C++.

After introduce you, I would like to ask if it's possible to get some help from you. Right now, I'm being able to build my addon but when I run the code I get:

node: symbol lookup error:
async-addon/build/Release/async.node: undefined symbol: tld_domain_to_lowercase

This is the code where I'm trying to use it:

#include <napi.h>
#include <iostream>
#include <stdlib.h>
#include <stdio.h>
#include "include/libtld/include/libtld/tld.h"

using namespace std;

Napi::Boolean TestingTld(const Napi::CallbackInfo& info) {
  Napi::Env env = info.Env();
  std::string arg = info[0].As<Napi::String>();
  const char *uri = arg.c_str();
  char *uri_lowercase = tld_domain_to_lowercase(uri);
  struct tld_info tldinfo;
  enum tld_result r;
  r = tld(uri_lowercase, &tldinfo);
  if(r == TLD_RESULT_SUCCESS) {
    const char *s = uri_lowercase + tldinfo.f_offset - 1;
    while(s > uri_lowercase)
    {
        if(*s == '.')
        {
            ++s;
            break;
        }
        --s;
    }
    printf("Sub-domain(s): \"%.*s\"\n", (int)(s - uri_lowercase), uri_lowercase);
    printf("Domain: \"%.*s\"\n", (int)(tldinfo.f_tld - s), s);
    printf("TLD: \"%s\"\n", tldinfo.f_tld);
  }
  return Napi::Boolean::New(env, true);
}


Napi::Object init(Napi::Env env, Napi::Object exports) {
    exports.Set(Napi::String::New(env, "TestingTld"), Napi::Function::New(env, TestingTld));
    return exports;
};

NODE_API_MODULE(async, init);

Thanks!

[AlexisWilke]

tld_domain_to_lowercase is a function found in the libtld library. (in "src/tld_domain_to_lowercase.c")

Check out your linkage. In C/C++, linking to libraries is not done automatically (that is, cl, the Microsoft compiler, has the capability to automatically link, but most compilers don't.) More or less, there are two command line options that are important when linking:

• -L <path> — specify a path where libraries can be searched for
• -l<name> — specify a library to link against, <name> is the library name without the lib or extension parts. So with libtld it would look ilke -ltld.

On our end we use cmake which makes it easier to generate the necessary command lines. The following would be what you're trying to do in cmake code:

target_link_libraries(${PROJECT_NAME}
    tld
)

But in your case it may be as easy as adding:

g++ ... -L path/to/libtd.so/here -ltld ...

If you're using cmake, you can see the command used by setting VERBOSE as in:

VERBOSE=1 make -C ../BUILD

The VERBOSE variable is checked and if set to non-zero the make script reacts by printing out all the command lines. That will show you whether any -L/-l exist for the libtld library.