René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Windows Node 26 enable_thin_lto=true breaks MSVC native addon builds (lldltojobs / -flto=thin)","articleBody":"### Version\n\n- Node.js `v26.5.0` (Windows x64)\n- `process.config.variables`: `clang=1`, `enable_thin_lto=true`, `enable_lto=false`, `llvm_version=19.1.5`\n- node-gyp `12.4.0`\n- Visual Studio 2026 Insiders / MSVC (`cl` / `link.exe`)\n\n### What goes wrong\n\nBuilding a native addon with `node-gyp rebuild` on this Node binary injects **Clang/lld thin-LTO flags** into the MSVC project:\n\n- compiler: `-flto=thin` (MSVC warns `D9002` and ignores)\n- linker: `/opt:lldltojobs=2` → **`LINK : fatal error LNK1117: 选项“opt:lldltojobs=2”中的语法错误`**\n\nReproduced while installing `@stoprocent/bluetooth-hci-socket@2.2.6` (dependency of `@stoprocent/noble` / `@stoprocent/bleno`). The package `binding.gyp` does **not** set these flags; they come from Node’s `common.gypi` LTO conditions once `enable_thin_lto` is true in the generated `build/config.gypi`.\n\nGenerated addon `config.gypi` snippet from the failed build:\n\n```text\n\"clang\": 0,\n\"enable_lto\": \"false\",\n\"enable_thin_lto\": \"true\",\n\"lto_jobs\": \"2\",\n```\n\nSo the addon build is treated as **non-clang MSVC** (`clang: 0`) while still enabling thin LTO options that only make sense for lld.\n\n### Expected\n\nAddon builds on Windows with MSVC should not inherit `enable_thin_lto` / lld-only linker options from the Node binary’s process config when the toolchain is MSVC.\n\nEither:\n\n1. Official Windows Node builds that still use MSVC for addons should ship `enable_thin_lto=false` in the config that node-gyp copies, or\n2. `common.gypi` should gate `-flto=thin` / `/opt:lldltojobs=…` on `clang==1` (and/or an lld linker), not only on `enable_thin_lto`.\n\n### Impact (downstream)\n\n- Deno/`npm` installs of optional BLE stacks fail hard on Windows under Node 26.5.0.\n- `@steve02081504/fount-p2p` documents whitelisting only `node-datachannel` scripts under Deno to avoid pulling these optional builds.\n\nWhen fixed: re-test `npm rebuild @stoprocent/bluetooth-hci-socket` (and Deno `--allow-scripts` for noble/bleno) on Windows Node 26+.\n","author":{"url":"https://github.com/steve02081504","@type":"Person","name":"steve02081504"},"datePublished":"2026-07-22T11:33:24Z","url":"https://github.com/nodejs/node/issues/64674"}