Postgres driver in NodeJS C++ Addon - c++

Question

I'm currently developing a C++ addon for NodeJS using the abstraction layer Nan. I would like to make a PostgreSQL request from this addon. But I get the following error:
module.js:597
return process.dlopen(module, path._makeLong(filename));
^
Error: ....cpp/build/Release/MyModule.node: undefined symbol: _ZTVN4pqxx14connect_directE
at Error (native)
at Object.Module._extensions..node (module.js:597:18)
at Module.load (module.js:487:32)
at tryModuleLoad (module.js:446:12)
at Function.Module._load (module.js:438:3)
at Module.require (module.js:497:17)
at require (internal/module.js:20:19)
at Object.<anonymous> (...cpp/test.js:1:77)
at Module._compile (module.js:570:32)
at Object.Module._extensions..js (module.js:579:10)
Here is my binding.gyp:
{
"targets": [
{
"target_name": "MyModule",
"sources": [ "Main.cpp"],
"include_dirs": [
"<!(node -e \"require('nan')\")"
],
"cflags": [
"-fexceptions",
"-lpq",
"-lpqxx"
],
"cflags_cc": [
"-fexceptions",
"-lpq",
"-lpqxx"
]
}
]
}
And my Main.cpp file
#include <nan.h>
#include <iostream>
#include <pqxx/pqxx>
using namespace Nan;
using namespace v8;
using namespace std;
using namespace pqxx;
NAN_METHOD(MyModule) {
// Database connection
connection C(
"dbname = ... \
user = ... \
password = ... \
hostaddr = 127.0.0.1 \
port = 5432");
}
NAN_MODULE_INIT(Init) {
Nan::Set(target, New<String>("MyModule").ToLocalChecked(),
GetFunction(New<FunctionTemplate>(MyModule)).ToLocalChecked());
}
NODE_MODULE(parser, Init)
I'm stuck with this error and I didn't find any solution on the web. I would be nice if someone could help!

Answer 1

dlopen tries to load a shared library. However, this library misses a symbol, _ZTVN4pqxx14connect_directE. To decode it:
$ c++filt _ZTVN4pqxx14connect_directE`
vtable for pqxx::connect_direct
Therefore, you need to link a library to your library (addon), which has this symbol. (The postgres driver?)
Make sure your build system doesn't delay the linking, and the lib appears when your run ldd your_addon. If the driver is installed to a non-standard directory, you can experiment with setting LD_LIBRARY_PATH, as a temporary solution.