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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/debug/src/lib.rs
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@@ -2,16 +2,10 @@
#![allow(clippy::cast_ptr_alignment)]
use alloc::string::String;
use alloc::vec::Vec;
use anyhow::Error;
use cranelift_codegen::isa::TargetFrontendConfig;
use faerie::{Artifact, Decl};
#[cfg(not(feature = "std"))]
use hashbrown::{hash_map, HashMap, HashSet};
use more_asserts::assert_gt;
#[cfg(feature = "std")]
use std::collections::{hash_map, HashMap, HashSet};
use target_lexicon::{BinaryFormat, Triple};
use wasmtime_environ::{ModuleAddressMap, ModuleVmctxInfo, ValueLabelsRanges};
@@ -24,8 +18,6 @@ mod read_debuginfo;
mod transform;
mod write_debuginfo;
extern crate alloc;
struct FunctionRelocResolver {}
impl SymbolResolver for FunctionRelocResolver {
fn resolve_symbol(&self, symbol: usize, addend: i64) -> ResolvedSymbol {
@@ -80,12 +72,12 @@ pub fn emit_debugsections_image(
assert_gt!(funcs.len(), 0);
let mut segment_body: (usize, usize) = (!0, 0);
for (body_ptr, body_len) in funcs {
segment_body.0 = ::core::cmp::min(segment_body.0, *body_ptr as usize);
segment_body.1 = ::core::cmp::max(segment_body.1, *body_ptr as usize + body_len);
segment_body.0 = std::cmp::min(segment_body.0, *body_ptr as usize);
segment_body.1 = std::cmp::max(segment_body.1, *body_ptr as usize + body_len);
}
let segment_body = (segment_body.0 as *const u8, segment_body.1 - segment_body.0);
let body = unsafe { ::core::slice::from_raw_parts(segment_body.0, segment_body.1) };
let body = unsafe { std::slice::from_raw_parts(segment_body.0, segment_body.1) };
obj.declare_with("all", Decl::function(), body.to_vec())?;
emit_dwarf(&mut obj, dwarf, &resolver)?;