Support for cross-platform executable generation

[HayDegha0917]

We have been using pkg for crating SEAs. One of the great features of pkg is its support for generating SEAs for a variety of target OSes (for example, create a Linux executable from a Windows workstation). It does not seem that NodeJS's SEA capability supports this. Is it possible to add as a feature?

[james-pre]

It should be possible to download Node.js executables for other platforms. You could instead download the target executable from the Node.js CDN instead of copying the installed node (step 4):

4. Create a copy of the node executable and name it according to your needs:

On systems other than Windows:

cp $(command -v node) hello

On Windows:

node -e "require('fs').copyFileSync(process.execPath, 'hello.exe')" 

From docs: Single executable applications

[HayDegha0917]

According to the documentation, "The version of the Node.js binary used to produce the blob must be the same as the one to which the blob will be injected." (see https://nodejs.org/api/single-executable-applications.html#generating-single-executable-preparation-blobs). Consequently, I don't think this approach will work.

[james-pre]

If you look at the structure of the blob:

struct SeaResource {
  SeaFlags flags = SeaFlags::kDefault;
  std::string_view code_path;
  std::string_view main_code_or_snapshot;
  std::optional<std::string_view> code_cache;
  std::unordered_map<std::string_view, std::string_view> assets;

  bool use_snapshot() const;
  bool use_code_cache() const;

  static constexpr size_t kHeaderSize = sizeof(kMagic) + sizeof(SeaFlags);
};

node/src/node_sea.h

There is nothing platform-dependent, so the same blob will be generated regardless of the platform (except maybe with endianness, though all modern kernels use little endian)

[HayDegha0917]

@james-pre OK I see that. But then why that admonition in the docs? The whole SEA thing is still very much work-in-progress, so maybe it's best to wait and see...?

[james-pre]

I believe they are referring to the Node version, not platform, since the struct can change between node versions (e.g. 18 and 20).

[james-pre]

I've implemented a CLI for generating cross-platform SEAs, called xsea (npm).

[DouglasAR01]

I tested it and worked flawlessly. Nice job!