try build emscripten without flags

[davidhewitt]

Possible companion to rust-lang/rust#151704

[davidhewitt]

@hoodmane any idea what happened here? It looks like nightly rust no longer wants to build cdylib crates for wasm, the only recent changes I see to the target spec is your PR to set_output_kind...

[hoodmane]

Yeah must be caused by that pr then. I'll look into it, thanks for the ping.

[hoodmane]

The flags are no longer necessary but should be harmless. By the way, it should be possible to build with stable rust 1.93.0.

[hoodmane]

Okay I'm reproducing this locally. Will look into it and hopefully fix it.

[hoodmane]

Okay the problem is related to crt_static. I changed it to be true by default since it is for the Emscripten main module, but it should be false for a dynamic library.

[hoodmane]

Okay here's the fix:
rust-lang/rust#152134
Thanks for catching this @davidhewitt !

[hoodmane]

And I confirmed that the nox job successfully builds a while when building against the stage1 compiler with my change. (Didn't run the tests but presumably the wheel actually works too...)

[davidhewitt]

👍 super, thanks. No worries about the ping, help much appreciated!

[hoodmane]

It's very exciting that we'll finally be able to build with stable Rust and no custom RUSTFLAGS.

[hoodmane]

Okay that landed so it should be available in the next nightly. If you wanted to work around it you can always pass -Ctarget-feature=-crt-static in your RUSTFLAGS.

[davidhewitt]

Hmm, it looks like stable Rust is producing a symbol (under the v0 name mangling scheme I think?) which is not supported by emcc. Not clear to me whether that's because it's incorrectly exporting that symbol, or just because it's an invalid internal symbol name at all.

[hoodmane]

Related?
https://github.com/pyodide/pyodide/blob/main/emsdk/patches/0002-Don-t-check-exports-for-being-valid-C-C-identifiers-.patch