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Migrate back to std:: stylistically (#554)

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* Migrate back to `std::` stylistically

This commit moves away from idioms such as `alloc::` and `core::` as
imports of standard data structures and types. Instead it migrates all
crates to uniformly use `std::` for importing standard data structures
and types. This also removes the `std` and `core` features from all
crates to and removes any conditional checking for `feature = "std"`

All of this support was previously added in #407 in an effort to make
wasmtime/cranelift "`no_std` compatible". Unfortunately though this
change comes at a cost:

* The usage of `alloc` and `core` isn't idiomatic. Especially trying to
  dual between types like `HashMap` from `std` as well as from
  `hashbrown` causes imports to be surprising in some cases.
* Unfortunately there was no CI check that crates were `no_std`, so none
  of them actually were. Many crates still imported from `std` or
  depended on crates that used `std`.

It's important to note, however, that **this does not mean that wasmtime
will not run in embedded environments**. The style of the code today and
idioms aren't ready in Rust to support this degree of multiplexing and
makes it somewhat difficult to keep up with the style of `wasmtime`.
Instead it's intended that embedded runtime support will be added as
necessary. Currently only `std` is necessary to build `wasmtime`, and
platforms that natively need to execute `wasmtime` will need to use a
Rust target that supports `std`. Note though that not all of `std` needs
to be supported, but instead much of it could be configured off to
return errors, and `wasmtime` would be configured to gracefully handle
errors.

The goal of this PR is to move `wasmtime` back to idiomatic usage of
features/`std`/imports/etc and help development in the short-term.
Long-term when platform concerns arise (if any) they can be addressed by
moving back to `no_std` crates (but fixing the issues mentioned above)
or ensuring that the target in Rust has `std` available.

* Start filling out platform support doc
This commit is contained in:
Alex Crichton
2019-11-19 00:04:06 -06:00
committed by Dan Gohman
parent c423a1c2f0
commit 39e57e3e9a
99 changed files with 271 additions and 444 deletions
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14
crates/runtime/src/lib.rs
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@@ -3,7 +3,6 @@
#![allow(improper_ctypes)]
#![deny(missing_docs, trivial_numeric_casts, unused_extern_crates)]
#![warn(unused_import_braces)]
#![cfg_attr(feature = "std", deny(unstable_features))]
#![cfg_attr(feature = "clippy", plugin(clippy(conf_file = "../../clippy.toml")))]
#![cfg_attr(
feature = "cargo-clippy",
@@ -22,9 +21,6 @@
clippy::use_self
)
)]
#![cfg_attr(not(feature = "std"), no_std)]
extern crate alloc;
mod export;
mod imports;
@@ -56,15 +52,5 @@ pub use crate::vmcontext::{
VMTableDefinition, VMTableImport,
};
#[cfg(not(feature = "std"))]
use hashbrown::{hash_map, HashMap, HashSet};
#[cfg(feature = "std")]
use std::collections::{hash_map, HashMap, HashSet};
#[cfg(not(feature = "std"))]
use spin::{RwLock, RwLockReadGuard, RwLockWriteGuard};
#[cfg(feature = "std")]
use std::sync::{RwLock, RwLockReadGuard, RwLockWriteGuard};
/// Version number of this crate.
pub const VERSION: &str = env!("CARGO_PKG_VERSION");