Rollup merge of #135948 - bjorn3:update_emscripten_std_tests, r=Mark-Simulacrum

Update emscripten std tests

This disables a bunch of emscripten tests that test things emscripten doesn't support and re-enables a whole bunch of tests which now work just fine on emscripten.

Tested with `EMCC_CFLAGS="-s MAXIMUM_MEMORY=2GB" ./x.py test library/ --target wasm32-unknown-emscripten`.

library/std/src/f64/tests.rs

@@ -112,7 +112,6 @@ fn test_neg_zero() {
     assert_eq!(Fp::Zero, neg_zero.classify());
 }
 
-#[cfg_attr(all(target_arch = "wasm32", target_os = "emscripten"), ignore)] // issue 42630
 #[test]
 fn test_one() {
     let one: f64 = 1.0f64;
@@ -165,7 +164,6 @@ fn test_is_finite() {
     assert!((-109.2f64).is_finite());
 }
 
-#[cfg_attr(all(target_arch = "wasm32", target_os = "emscripten"), ignore)] // issue 42630
 #[test]
 fn test_is_normal() {
     let nan: f64 = f64::NAN;
@@ -183,7 +181,6 @@ fn test_is_normal() {
     assert!(!1e-308f64.is_normal());
 }
 
-#[cfg_attr(all(target_arch = "wasm32", target_os = "emscripten"), ignore)] // issue 42630
 #[test]
 fn test_classify() {
     let nan: f64 = f64::NAN;

library/std/src/io/copy/tests.rs

@@ -126,6 +126,7 @@ mod io_benches {
     use crate::io::prelude::*;
 
     #[bench]
+    #[cfg_attr(target_os = "emscripten", ignore)] // no /dev
     fn bench_copy_buf_reader(b: &mut Bencher) {
         let mut file_in = File::open("/dev/zero").expect("opening /dev/zero failed");
         // use dyn to avoid specializations unrelated to readbuf

library/std/src/io/tests.rs

@@ -7,7 +7,6 @@ use crate::mem::MaybeUninit;
 use crate::ops::Deref;
 
 #[test]
-#[cfg_attr(target_os = "emscripten", ignore)]
 fn read_until() {
     let mut buf = Cursor::new(&b"12"[..]);
     let mut v = Vec::new();
@@ -359,7 +358,6 @@ fn chain_zero_length_read_is_not_eof() {
 }
 
 #[bench]
-#[cfg_attr(target_os = "emscripten", ignore)]
 #[cfg_attr(miri, ignore)] // Miri isn't fast...
 fn bench_read_to_end(b: &mut test::Bencher) {
     b.iter(|| {

library/std/src/sys/alloc/wasm.rs

@@ -1,6 +1,6 @@
 //! This is an implementation of a global allocator on wasm targets when
-//! emscripten is not in use. In that situation there's no actual runtime for us
-//! to lean on for allocation, so instead we provide our own!
+//! emscripten or wasi is not in use. In that situation there's no actual runtime
+//! for us to lean on for allocation, so instead we provide our own!
 //!
 //! The wasm instruction set has two instructions for getting the current
 //! amount of memory and growing the amount of memory. These instructions are the

library/std/src/sys/pal/wasi/mod.rs

@@ -1,8 +1,7 @@
 //! System bindings for the wasm/web platform
 //!
 //! This module contains the facade (aka platform-specific) implementations of
-//! OS level functionality for wasm. Note that this wasm is *not* the emscripten
-//! wasm, so we have no runtime here.
+//! OS level functionality for wasm.
 //!
 //! This is all super highly experimental and not actually intended for
 //! wide/production use yet, it's still all in the experimental category. This

library/std/src/sys/pal/wasm/mod.rs

@@ -2,7 +2,7 @@
 //!
 //! This module contains the facade (aka platform-specific) implementations of
 //! OS level functionality for wasm. Note that this wasm is *not* the emscripten
-//! wasm, so we have no runtime here.
+//! or wasi wasm, so we have no runtime here.
 //!
 //! This is all super highly experimental and not actually intended for
 //! wide/production use yet, it's still all in the experimental category. This