Node-ffi Bindings to An array of NULL terminated C strings, but got `Segmentation fault: 11`

Question

I am using Node-ffi to write a Node bindings for MITIE. But I got problem,

The argument of a function is char**: An array of NULL terminated C strings, like this:

int run (char** tokens)
{
    try
    {
        std::vector<std::string> words;
        for (unsigned long i = 0; tokens[i]; ++i)
            words.push_back(tokens[i]);

        return 1;
    }
    catch(...)
    {
        return 0;
    }
}

And this is what I did use ffi:

const ffi = require('ffi');
const ArrayType = require('ref-array');

const StringArray = ArrayType('string')

const test = ffi.Library('test', {
  'run': [ 'int', [StringArray] ]
});

test.run(['a', 'b']);

But I got: Segmentation fault: 11.

I uploaded the sample code to this repo.

And in this repo you also can see I have wrote a Python bindings by ctypes, It runs well.

Here is my operating environment:

• [email protected]
• [email protected]
• darwin x64 17.0.0
• MacBook Pro (13-inch, 2016, Four Thunderbolt 3 Ports)
• macOS 10.13

Answer 1

You have to explicitly terminate token array with NULL:

const ffi = require('ffi');
const ArrayType = require('ref-array');
const ref = require('ref');

const StringArray = ArrayType('string')

const test = ffi.Library('test', {
  'run': [ 'int', [StringArray] ]
});

console.log(test.run(['a', 'b', ref.NULL])); // -> 2