ffi: JavaScript wrappers make non-constructible native functions constructible

[trivikr]

Version

main

Platform

macOS 26.6.0

Subsystem

ffi

What steps will reproduce the bug?

repro.c

#include <stdint.h>
#include <stdio.h>

int32_t add_i32(int32_t a, int32_t b) {
 fprintf(stderr, "native add_i32 invoked: %d + %d\n", a, b);
 return a + b;
}

double multiply_f64(double a, double b) {
 return a * b;
}

repro.js

import { dlopen, suffix } from 'node:ffi';

const { functions } = dlopen(`./repro.${suffix}`, {
 add_i32: {
 arguments: ['i32', 'i32'],
 return: 'i32',
 },
 multiply_f64: {
 arguments: ['f64', 'f64'],
 return: 'f64',
 },
});

const { add_i32, multiply_f64 } = functions;

console.log(
 'add_i32 has own prototype:',
 Object.hasOwn(add_i32, 'prototype'),
);

try {
 Reflect.construct(add_i32, [20, 22]);
 console.log('Reflect.construct(add_i32): succeeded');
} catch (error) {
 console.log(
 'Reflect.construct(add_i32):',
 `${error.name}: ${error.message}`,
 );
}

console.log(
 'multiply_f64 has own prototype:',
 Object.hasOwn(multiply_f64, 'prototype'),
);

try {
 Reflect.construct(multiply_f64, [6, 7]);
 console.log('Reflect.construct(multiply_f64): succeeded');
} catch (error) {
 console.log(
 'Reflect.construct(multiply_f64):',
 `${error.name}: ${error.message}`,
 );
}

Commands to run:

$ cc -dynamiclib -o repro.dylib repro.c

$ node --no-warnings --experimental-ffi repro.js

How often does it reproduce? Is there a required condition?

Always

What is the expected behavior? Why is that the expected behavior?

Wrapped functions should preserve the native function’s non-constructible behavior: no own .prototype, and Reflect.construct() should throw a TypeError without invoking native code.

What do you see instead?

add_i32 has own prototype: true
native add_i32 invoked: 20 + 22
Reflect.construct(add_i32): succeeded
multiply_f64 has own prototype: false
Reflect.construct(multiply_f64): TypeError: function multiply_f64() { [native code] } is not a constructor

Wrapped native functions such as add_i32 gain an own .prototype, and Reflect.construct(add_i32, [20, 22]) succeeds and invokes native code.

Additional information

No response