René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"ffi: memory helpers return undefined instead of throwing when a required argument is omitted","articleBody":"### Version\n\nmain (a48e33fb6f8e48be856da69692a17bc19a39317a)\n\n### Platform\n\n```text\nDarwin 25.5.0 Darwin Kernel Version 25.5.0: Tue Jun  9 22:28:34 PDT 2026; root:xnu-12377.121.10~1/RELEASE_ARM64_T6041 arm64\n```\n\n### Subsystem\n\nffi\n\n### What steps will reproduce the bug?\n\n```js\n// node --experimental-ffi repro.js\nconst ffi = require('node:ffi');\n\nconsole.log(ffi.getUint8());    // pointer omitted\nconsole.log(ffi.setUint8());    // pointer omitted\nconsole.log(ffi.toBuffer(1n));  // length omitted\n\n// The same arguments, passed explicitly.\ntry { ffi.getUint8(undefined); } catch (err) { console.log(err.message); }\ntry { ffi.toBuffer(1n, undefined); } catch (err) { console.log(err.message); }\n```\n\n### How often does it reproduce? Is there a required condition?\n\nAlways. All 22 helpers behave the same way: the ten getters, the ten setters, `toBuffer()` and `toArrayBuffer()`.\n\n### What is the expected behavior? Why is that the expected behavior?\n\nOmitting a required argument should throw, like passing it explicitly as `undefined` already does.\n\nThe documented signatures are `ffi.getInt8(pointer[, offset])`, `ffi.setInt8(pointer, offset, value)` and `ffi.toBuffer(pointer, length[, copy])`, and the getters are documented to return a `number` or a `bigint`. The helpers are inconsistent among themselves too: `setUint8(ptr)` throws `Expected an offset argument`, so only a missing first argument goes unreported.\n\n### What do you see instead?\n\n```text\nundefined\nundefined\nundefined\nThe pointer must be a bigint\nThe length must be a number\n```\n\n`GetValidatedPointerAddress()` and `GetValidatedSize()` already reject `undefined`. The `args.Length()` test in front of them short-circuits the call and returns `Nothing` without scheduling an exception:\n\nhttps://github.com/nodejs/node/blob/a48e33fb6f8e48be856da69692a17bc19a39317a/src/ffi/data.cc#L163-L169\n\nThe same shape guards the setters (`L207`), the length of `ToBuffer()` (`L559`) and of `ToArrayBuffer()` (`L621`), and both arguments of `ExportBytes()` (`L697`, `L703`).\n\n### Additional information\n\nThese are raw memory helpers, so the silent `undefined` is easy to miss: `if (ffi.getUint8(ptr))` written with the pointer left out is falsy exactly like a zero byte, and `ffi.setUint8()` reports success for a write that never happened.\n\nThe tests do not look deliberate. `FunctionCallbackInfo::operator[]` returns `Undefined` for an out-of-range index, which is exactly the value these validators reject, and these six are the only tests in `src/` where `args.Length()` can skip a call that throws (the only other `Length()` tests that guard a call at all guard `Buffer::HasInstance()`, which cannot throw). They arrived with the module in d0fa608c079 and survived fe41105dddc (#62858), which reworked the surrounding error handling; I found no mention of argument count in the reviews of #62072, #62762 or #62858.\n\nRefs: https://github.com/nodejs/node/pull/62072\nRefs: https://github.com/nodejs/node/pull/62858\nRefs: https://github.com/nodejs/node/pull/65342\n","author":{"url":"https://github.com/soulee-dev","@type":"Person","name":"soulee-dev"},"datePublished":"2026-08-23T07:19:23Z","url":"https://github.com/nodejs/node/issues/65499"}