René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"ffi: optimized fast pointer BigInts bypass range validation","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__attribute__((visibility(\"default\")))\nvoid* identity_pointer(void* ptr) {\n  return ptr;\n}\n```\n\n`repro.js`\n```js\nimport { dlopen } from 'node:ffi';\n\nconst { lib, functions } = dlopen('./repro.dylib', {\n  identity_pointer: { arguments: ['pointer'], return: 'pointer' },\n});\n\nconst identityPointer = functions.identity_pointer;\n\nfunction show(label, fn) {\n  try {\n    console.log(`${label}:`, String(fn()));\n  } catch (err) {\n    console.log(`${label}:`, err.code || err.name);\n  }\n}\n\nshow('cold -1n', () => identityPointer(-1n));\n\n%PrepareFunctionForOptimization(identityPointer);\nidentityPointer(0n);\nidentityPointer(0n);\n%OptimizeFunctionOnNextCall(identityPointer);\nidentityPointer(0n);\n\nshow('optimized -1n', () => identityPointer(-1n));\nshow('optimized 2^64+5', () => identityPointer((1n \u003c\u003c 64n) + 5n));\n\nlib.close();\n```\n\nRun\n```console\n$ cc -dynamiclib -o repro.dylib repro.c\n\n$ node --no-warnings --experimental-ffi --allow-natives-syntax 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\n```console\ncold -1n: ERR_INVALID_ARG_VALUE\noptimized -1n: ERR_INVALID_ARG_VALUE\noptimized 2^64+5: ERR_INVALID_ARG_VALUE\n```\n\nOptimized fast calls to match generic and shared-buffer validation and throw `ERR_INVALID_ARG_VALUE`.\n\n### What do you see instead?\n\n```console\ncold -1n: ERR_INVALID_ARG_VALUE\noptimized -1n: 18446744073709551615\noptimized 2^64+5: 5\n```\n\ncold `-1n` throws, but after optimizing the FFI wrapper `-1n` is passed as `2^64 - 1` and `2^64 + 5` is passed as `5`\n\n### Additional information\n\n_No response_","author":{"url":"https://github.com/trivikr","@type":"Person","name":"trivikr"},"datePublished":"2026-08-05T01:59:00Z","url":"https://github.com/nodejs/node/issues/65031"}