Building wgpu client with trace enabled for wasm fails

[blakej11]

Description
I have a project based on current wgpu (commit e27fbb8). When building it for wasm, I compile it with RUSTFLAGS=--cfg=web_sys_unstable_apis cargo build --no-default-features --target wasm32-unknown-unknown. When I try to build it with the "trace" feature enabled in its wgpu dependency, it fails while trying to build libloading 0.7.0; the errors are of the form:

error[E0433]: failed to resolve: use of undeclared crate or module `imp`
  --> /Users/blakej/.cargo/registry/src/github.com-1ecc6299db9ec823/libloading-0.7.0/src/lib.rs:63:20
   |
63 | pub struct Library(imp::Library);
   |                    ^^^ use of undeclared crate or module `imp`

The problem is presumably that libloading is being compiled at all, which doesn't seem to make sense for a wasm target.

I wasn't able to figure out exactly what was inducing it to be compiled, but I noticed that if I removed the "wgc/trace" entry in the trace feature in wgpu/wgpu/Cargo.toml (in a local copy of wgpu), it stopped trying to pull in that dependency.

Platform
macOS 11.4, wgpu snapshot listed above.

[kvark]

Hmm, nothing obvious here:

wgpu/wgpu-core/Cargo.toml

Line 17 in e27fbb8

trace = ["ron", "serde", "wgt/trace", "arrayvec/serde", "naga/serialize"]

At the same time, trace feature isn't usable in wasm at all, so this isn't a blocker for anyone.

[RodogInfinite]

I got the same issue when trying to run the examples on the web with a local copy of this repo. It looks like this might be solved with libloading 0.7.2 according to Fails to build to wasm32-unknown-unknown target #91 . I'm not sure where exactly the solution should be implemented though since I'm just getting started by running examples.

[kvark]

we could just require libloading 0.7.2 in the dependencies (instead of 0.7)

[teoxoy]

There has recently been some work improving which features get enabled depending on platform.

@blakej11 @RodogInfinite is this still an issue on current master (try forcing libloading 0.7.0)?