René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"ffi: JavaScript wrappers make non-constructible native functions constructible","articleBody":"### Version\n\nmain\n\n### Platform\n\n```text\nmacOS 26.6.0\n```\n\n### Subsystem\n\nffi\n\n### What steps will reproduce the bug?\n\n`repro.c`\n```c\n#include \u003cstdint.h>\n#include \u003cstdio.h>\n\nint32_t add_i32(int32_t a, int32_t b) {\n  fprintf(stderr, \"native add_i32 invoked: %d + %d\\n\", a, b);\n  return a + b;\n}\n\ndouble multiply_f64(double a, double b) {\n  return a * b;\n}\n```\n\n`repro.js`\n```js\nimport { dlopen, suffix } from 'node:ffi';\n\nconst { functions } = dlopen(`./repro.${suffix}`, {\n  add_i32: {\n    arguments: ['i32', 'i32'],\n    return: 'i32',\n  },\n  multiply_f64: {\n    arguments: ['f64', 'f64'],\n    return: 'f64',\n  },\n});\n\nconst { add_i32, multiply_f64 } = functions;\n\nconsole.log(\n  'add_i32 has own prototype:',\n  Object.hasOwn(add_i32, 'prototype'),\n);\n\ntry {\n  Reflect.construct(add_i32, [20, 22]);\n  console.log('Reflect.construct(add_i32): succeeded');\n} catch (error) {\n  console.log(\n    'Reflect.construct(add_i32):',\n    `${error.name}: ${error.message}`,\n  );\n}\n\nconsole.log(\n  'multiply_f64 has own prototype:',\n  Object.hasOwn(multiply_f64, 'prototype'),\n);\n\ntry {\n  Reflect.construct(multiply_f64, [6, 7]);\n  console.log('Reflect.construct(multiply_f64): succeeded');\n} catch (error) {\n  console.log(\n    'Reflect.construct(multiply_f64):',\n    `${error.name}: ${error.message}`,\n  );\n}\n```\n\nCommands to run:\n```sh\n$ cc -dynamiclib -o repro.dylib repro.c\n\n$ node --no-warnings --experimental-ffi repro.js\n```\n\n### How often does it reproduce? Is there a required condition?\n\nAlways\n\n### What is the expected behavior? Why is that the expected behavior?\n\nWrapped functions should preserve the native function’s non-constructible behavior: no own `.prototype`, and `Reflect.construct()` should throw a `TypeError` without invoking native code.\n\n### What do you see instead?\n\n```console\nadd_i32 has own prototype: true\nnative add_i32 invoked: 20 + 22\nReflect.construct(add_i32): succeeded\nmultiply_f64 has own prototype: false\nReflect.construct(multiply_f64): TypeError: function multiply_f64() { [native code] } is not a constructor\n```\n\nWrapped native functions such as `add_i32` gain an own `.prototype`, and `Reflect.construct(add_i32, [20, 22])` succeeds and invokes native code.\n\n### Additional information\n\n_No response_","author":{"url":"https://github.com/trivikr","@type":"Person","name":"trivikr"},"datePublished":"2026-08-10T05:41:53Z","url":"https://github.com/nodejs/node/issues/65183"}