ship .idl files rather than .h files for windows SDK

[andrewrk]

This is a toolchain installation size optimization.

Many of the C header files Zig ships that come from mingw-w64 have this header:

/*** Autogenerated by WIDL 8.5 from include/xpsrassvc.idl - Do not edit ***/

If we compare total file sizes, it comes out to roughly 40 MiB reduced to 10 MiB:

[nix-shell:~/Downloads/mingw-w64/mingw-w64-headers]$ cat $(find -name "*.idl") | wc -c
10436832

[nix-shell:~/Downloads/mingw-w64/mingw-w64-headers]$ cat $(grep -RIl "Autogenerated by WIDL") | wc -c
41764448

In terms of tarball size it's roughly 2.4 MiB to 724 KB:

[nix-shell:~/Downloads/mingw-w64/mingw-w64-headers]$ cat $(find -name "*.idl") | xz | wc -c
740960

[nix-shell:~/Downloads/mingw-w64/mingw-w64-headers]$ cat $(grep -RIl "Autogenerated by WIDL") | xz | wc -c
2490188

A prerequisite for this issue would be a WIDL implementation in Zig. That could be a fun project for a contributor.

[odecaux]

Exposing such a parser to the user would enable generating bindings to the COM and WinRT APIs.

[nektro]

is this the same IDL that's https://webidl.spec.whatwg.org ?

edit: hmm there are similarities but I think its different
https://android.googlesource.com/toolchain/mingw/+/refs/heads/main/mingw-w64-v6.x/mingw-w64-headers/include/xpsrassvc.idl

[Paul-Dempsey]

Microsoft Windows IDL: https://learn.microsoft.com/en-us/uwp/midl-3/

[andrewrk]

Wine has an implementation you can look at. There's also one in mingw-w64 which may or may not just be the code ported from Wine.

[xinlifoobar]

Do you suggest using the wine implementation, e.g. zig with cpp bindings, or pure zig solution? I'm interested in the latter.

[andrewrk]

Pure zig solution, obviously :-)

[sno2]

Is the status of this issue changed by #16269 (comment)?

[NyuB]

I would be interested in having a look at this, could you clarify the intended outcome, what options are you considering for this widl integration ?

• No language change:
  • translate the distributed .idl files to .h files once at first usage, which will reduce the distributed tarball size but not the installed files
• A builtin command similar or within @cImport like @idlImport("stuff.idl"), and this could either
  • produce C header content from the IDL file on the fly then feed them to the existing @cImport mecanism
  • directly produce Zig's ast nodes from the IDL without the above indirection
• Something else ?