Zig and Node.js N-API example #3000
Comments
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It seems like n-api requires that modules register themselves from constructors that run when their dll is opened. If you don't then node's
This issue will require a way to register a dynamic library constructor. The code I was playing with: // https://nodejs.org/api/n-api.html
const std = @import("std");
const napi = @cImport({
@cInclude("node_api.h");
});
fn NAPI_MODULE_X(modname: []const u8, regfunc: napi.napi_addon_register_func, priv: ?*c_void, flags: c_uint) void {
napi_module_register(&napi_module {
.nm_version = napi.NAPI_MODULE_VERSION,
.nm_flags = flags,
.nm_filename = null,
.nm_register_func = regfunc,
.nm_modname = modname,
.nm_priv = priv,
.reserved = c_void(null) ** 4,
});
}
fn NAPI_MODULE(modname: []const u8, regfunc: napi.napi_addon_register_func) void {
return NAPI_MODULE_X(modname, regfunc, null, 0);
}
extern fn myfunc(env: napi.napi_env, exports: napi.napi_value) napi.napi_value {
var answer: napi.napi_value = undefined;
var status: napi.napi_status = undefined;
status = napi.napi_create_int64(env, 42, &answer);
if (status != .napi_ok) return null;
status = napi.napi_set_named_property(env, exports, &"answer", answer);
if (status != .napi_ok) return null;
return exports;
}
comptime {
@export("napi_register_module_v1", myfunc, .Strong);
} |
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I have managed to do exactly that thanks to the help of the nice zig people in freenode by doing that on linux: export const init_array linksection(".init_array") = [_]extern fn () void {
myFunc
}; |
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@andrewrk this issue is a good example use case for why we need the ability to support constructors. The workaround found is linux and elf specific. |
SpexGuy
added
the
use case
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Since you need to link C code anyways for this use case, I think calling your constructor from C is a perfectly fine solution and avoids adding any language features to support this use case. The C file can be as simple as #include <node_api.h>
napi_value init(napi_env env, napi_value exports);
NAPI_MODULE(NODE_GYP_MODULE_NAME, init)Example repo here: /~https://github.com/ifreund/zig-napi-example |
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It turns out I wasn't actually satisfied with that solution. I'm not sure if this has changed since @daurnimator's initial investigation, but node no longer requires the constructor to be run if the module exports a function with the proper name: For example: const c = @cImport({
@cInclude("node_api.h");
});
export fn napi_register_module_v1(env: c.napi_env, exports: c.napi_value) c.napi_value {
var function: c.napi_value = undefined;
if (c.napi_create_function(env, null, 0, foo, null, &function) != .napi_ok) {
_ = c.napi_throw_error(env, null, "Failed to create function");
return null;
}
if (c.napi_set_named_property(env, exports, "foo", function) != .napi_ok) {
_ = c.napi_throw_error(env, null, "Failed to add function to exports");
return null;
}
return exports;
}
fn foo(env: c.napi_env, info: c.napi_callback_info) callconv(.C) c.napi_value {
var result: c.napi_value = undefined;
if (c.napi_create_int32(env, 42, &result) != .napi_ok) {
_ = c.napi_throw_error(env, null, "Failed to create return value");
return null;
}
return result;
}const example = require('./example.node');
console.log(example.foo());build with |
Looks like it might have, e.g. nodejs/node#26175 |
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Hi @ifreund - thanks for the example! I ran into some problems trying to get it to run zig 0.9.0-dev.1583+a7d215759:
I then ended up with the following code: const c = @cImport({
@cInclude("node_api.h");
});
export fn napi_register_module_v1(env: c.napi_env, exports: c.napi_value) c.napi_value {
var function: c.napi_value = undefined;
if (c.napi_create_function(env, null, 0, foo, null, &function) != 0) {
_ = c.napi_throw_error(env, null, "Failed to create function");
return null;
}
if (c.napi_set_named_property(env, exports, "foo", function) != 0) {
_ = c.napi_throw_error(env, null, "Failed to add function to exports");
return null;
}
return exports;
}
fn foo(env: c.napi_env, _: c.napi_callback_info) callconv(.C) c.napi_value {
var result: c.napi_value = undefined;
if (c.napi_create_int32(env, 42, &result) != 0) {
_ = c.napi_throw_error(env, null, "Failed to create return value");
return null;
}
return result;
}I tried running this on Debian Linux and it seems to work as expected (nice!): However, I was not successful in getting this to run on macOS 12.0.1: /~https://github.com/kristoff-it/zig-cuckoofilter/blob/master/c-abi-examples/node_example.js#L13-L17 seems to imply macOS might need a different approach, but I tried doing a |
This is the same error you'd traditionally get for C if you forgot to specify |
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Thanks! I tried the same command with |
We now respect both `-fallow-shlib-undefined` and `-Wl,"-undefined=dynamic_lookup"` flags. This is the first step towards solving issues #8180 and #3000. We currently do not expose any other ld64 equivalent flag for `-undefined` flag - we basically throw an error should the user specify a different flag. Support for those is conditional on closing #8180. As a result of this change, it is now possible to generate a valid native Node.js addon with Zig for macOS.
We now respect both `-fallow-shlib-undefined` and `-Wl,"-undefined=dynamic_lookup"` flags. This is the first step towards solving issues #8180 and #3000. We currently do not expose any other ld64 equivalent flag for `-undefined` flag - we basically throw an error should the user specify a different flag. Support for those is conditional on closing #8180. As a result of this change, it is now possible to generate a valid native Node.js addon with Zig for macOS.
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BTW, this repo implements a module with self-registration: /~https://github.com/staltz/zig-nodejs-example/blob/main/src/lib.zig#L6-L9 |
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Hey, it seems its not fixed on Windows, trying to compile with |
Me too, is there something we're missing? |
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I think maybe you're missing the import library which is required on windows, see for example /~https://github.com/scheibo/zigpkg/blob/main/build.zig#L57-L61. This can usually be found relative on the headers /~https://github.com/scheibo/zigpkg/blob/main/src/bin/install-zigpkg#L240-L268 |
Oh! That's right! I didn't download Thank you. On a side note: I found that the link can be obtained directly from |
Given Zig's promise of C header includes, it would be cool for the docs or blog to have an example of writing a "Hello Node.js" native addon for Node.js using N-API and Zig.
Node's N-API is fairly recent, and many existing native addons for Node written using Nan etc. are probably being ported. Now might be a great time for some of these native Node modules to consider using Zig instead of C/C++.
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