Static variables are not exported when targeting wasm32-unknown-unknown

[Jake-Shadle]

It appears that #67453 has regressed in nightly, The last working nightly we used was rustc 1.56.0-nightly (0fa319039 2021-08-12), every nightly from rustc 1.56.0-nightly (5a19ffe1c 2021-08-13) to the present has failed.

I tried this code:

// lib.rs
#[no_mangle]
#[used]
pub static FOO: u64 = 4242;

I expected to see this happen:

cargo build --release --target wasm32-unknown-unknown && wasm2wat target/wasm32-unknown-unknown/release/missing_symbols.wasm

In rustc 1.54.0 (a178d0322 2021-07-26), this properly exports the FOO static.

(module
  (table (;0;) 1 1 funcref)
  (memory (;0;) 17)
  (global (;0;) (mut i32) (i32.const 1048576))
  (global (;1;) i32 (i32.const 1048576))
  (global (;2;) i32 (i32.const 1048584))
  (global (;3;) i32 (i32.const 1048584))
  (export "memory" (memory 0))
  (export "FOO" (global 1))
  (export "__data_end" (global 2))
  (export "__heap_base" (global 3))
  (data (;0;) (i32.const 1048576) "\92\10\00\00\00\00\00\00"))

Instead, this happened:

cargo +nightly build --release --target wasm32-unknown-unknown && wasm2wat target/wasm32-unknown-unknown/release/missing_symbols.wasm

In rustc 1.56.0-nightly (2d2bc94c8 2021-08-15), FOO is not exported.

(module
  (table (;0;) 1 1 funcref)
  (memory (;0;) 16)
  (global (;0;) (mut i32) (i32.const 1048576))
  (global (;1;) i32 (i32.const 1048576))
  (global (;2;) i32 (i32.const 1048576))
  (export "memory" (memory 0))
  (export "__data_end" (global 1))
  (export "__heap_base" (global 2)))

Note that unlike in the previous bug reported in #67453, using -C link-dead-code does not export FOO.

Meta

rustc --version --verbose:

rustc 1.56.0-nightly (2d2bc94c8 2021-08-15)
binary: rustc
commit-hash: 2d2bc94c8c3aa778e191f80261c726e4777439f1
commit-date: 2021-08-15
host: x86_64-unknown-linux-gnu
release: 1.56.0-nightly
LLVM version: 12.0.1

[lqd]

@Jake-Shadle I feel/hope #88032 will fix it. It should be in the next nightly, so please test it out and let us know :)

[Jake-Shadle]

Hah yes, indeed, rustc 1.56.0-nightly (0035d9dce 2021-08-16) made the build go green again, thanks!

I'll close this now, but I guess I am a bit concerned about how this regression could occur since the original PR #67975 included a test specifically for this case, which is still present https://github.com/rust-lang/rust/blob/master/src/test/run-make/wasm-export-all-symbols/verify.js

[lqd]

@Jake-Shadle wasm32-unknown-unknown is a tier 2 target, IIRC tests are not always run and if they fail, it doesn't stop a nightly from being released.

As anecdote, this issue was noticed not because of the wasm tests, but because of miri's tests: they are executed after PRs land (except during "no breaking the tools"-week before release) because a tool can similarly be temporarily broken, but people are notified when its tests fail.

[Jake-Shadle]

Ahh right, sorry, forgot wasm32 was still a tier 2, thanks for noticing this and linking the fix!