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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"ffi: setFloat32()/setFloat64() coerce their value and discard a pending exception","articleBody":"### Version\n\nmain (ad7a5b8302ae54b6e6dc77e03eabc5a3218dfb85)\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 { getRawPointer, setFloat64, getFloat64 } = require('node:ffi');\n\nconst ptr = getRawPointer(Buffer.alloc(8));\n\nfor (const value of ['1.5', true, {}, null]) {\n  setFloat64(ptr, 0, value);\n  console.log(`setFloat64(${String(value)}) ->`, getFloat64(ptr, 0));\n}\n\ntry {\n  setFloat64(ptr, 0, { valueOf() { throw new RangeError('boom'); } });\n} catch (err) {\n  console.log('valueOf threw ->', err.name, err.message);\n}\n```\n\n### How often does it reproduce? Is there a required condition?\n\nAlways. `setFloat32()` behaves the same way.\n\n### What is the expected behavior? Why is that the expected behavior?\n\n`setFloat32()` and `setFloat64()` should reject a value that is not a `number`, like every other setter in the module, and they should not replace an exception the value itself threw.\n\nThe same `double` is type-checked on the argument path, where `ToFFIArgument()` requires `IsNumber()` and throws `Argument %s must be a double`, and the documentation says the setters \"validate the supplied JavaScript value against the target native type before writing it into memory\".\n\n### What do you see instead?\n\n```text\nsetFloat64(1.5) -> 1.5\nsetFloat64(true) -> 1\nsetFloat64([object Object]) -> NaN\nsetFloat64(null) -> 0\nvalueOf threw -> TypeError Value must be a number\n```\n\nThe integer branches of `SetValue\u003cT>()` require `IsNumber()` before any range check, but the floating-point branch calls `ToNumber()` and casts the result. When `ToNumber()` itself fails, the `ERR_INVALID_ARG_VALUE` overwrites the exception it left pending, so the `RangeError` never reaches the caller. `DataView.prototype.setFloat64()` and `Buffer.prototype.writeDoubleLE()` both propagate it.\n\nhttps://github.com/nodejs/node/blob/ad7a5b8302ae54b6e6dc77e03eabc5a3218dfb85/src/ffi/data.cc#L402-L411\n\n### Additional information\n\nThe setters write straight into native memory, so a `'1,5'` typo from a config file stores `NaN` in a struct field with no error at the call site. `setInt32()` throws on the same mistake.\n\n`DataView` and `Buffer` coerce here too, but they coerce for integers as well (`dv.setInt8(0, 300)` writes `44`), while `node:ffi` rejects those.\n\nThe integer validation, the float coercion and the documentation sentence all landed together in d0fa608c079, the floating-point branch has not been modified since, and I found no review comment about the difference in the pull requests that touched it.\n\nRefs: https://github.com/nodejs/node/pull/62072\nRefs: https://github.com/nodejs/node/pull/62762\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":"2026-08-17T00:27:49Z","url":"https://github.com/nodejs/node/issues/65341"}