Make more code work with no_std. (#407)

* Make more code work with no_std.

no_std support is still incomplete, but this patch takes care of the
bulk of the straightforward parts.

wasmtime-runtime/src/imports.rs

@@ -1,8 +1,8 @@
 use crate::instance::InstanceHandle;
 use crate::vmcontext::{VMFunctionImport, VMGlobalImport, VMMemoryImport, VMTableImport};
+use crate::HashSet;
 use cranelift_entity::{BoxedSlice, PrimaryMap};
 use cranelift_wasm::{FuncIndex, GlobalIndex, MemoryIndex, TableIndex};
-use std::collections::HashSet;
 
 /// Resolved import pointers.
 #[derive(Clone)]

wasmtime-runtime/src/instance.rs

@@ -15,9 +15,15 @@ use crate::vmcontext::{
     VMGlobalDefinition, VMGlobalImport, VMMemoryDefinition, VMMemoryImport, VMSharedSignatureIndex,
     VMTableDefinition, VMTableImport,
 };
+use crate::{HashMap, HashSet};
+use alloc::borrow::ToOwned;
+use alloc::boxed::Box;
+use alloc::rc::Rc;
+use alloc::string::{String, ToString};
 use core::any::Any;
 use core::borrow::Borrow;
 use core::cell::RefCell;
+use core::convert::TryFrom;
 use core::slice;
 use core::{mem, ptr};
 use cranelift_entity::EntityRef;
@@ -27,12 +33,6 @@ use cranelift_wasm::{
     GlobalIndex, GlobalInit, MemoryIndex, SignatureIndex, TableIndex,
 };
 use indexmap;
-use std::borrow::ToOwned;
-use std::boxed::Box;
-use std::collections::{HashMap, HashSet};
-use std::convert::TryFrom;
-use std::rc::Rc;
-use std::string::{String, ToString};
 use wasmtime_environ::{DataInitializer, Module, TableElements, VMOffsets};
 
 fn signature_id(
@@ -613,9 +613,9 @@ impl Instance {
     }
 
     pub(crate) fn lookup_global_export(&self, field: &str) -> Option<Export> {
-        let cell: &RefCell<HashMap<std::string::String, core::option::Option<Export>>> =
+        let cell: &RefCell<HashMap<alloc::string::String, core::option::Option<Export>>> =
             self.global_exports.borrow();
-        let map: &mut HashMap<std::string::String, core::option::Option<Export>> =
+        let map: &mut HashMap<alloc::string::String, core::option::Option<Export>> =
             &mut cell.borrow_mut();
         if let Some(Some(export)) = map.get(field) {
             return Some(export.clone());
@@ -790,10 +790,10 @@ impl InstanceHandle {
 
         // Collect the exports for the global export map.
         for (field, decl) in &instance.module.exports {
-            use std::collections::hash_map::Entry::*;
-            let cell: &RefCell<HashMap<std::string::String, core::option::Option<Export>>> =
+            use crate::hash_map::Entry::*;
+            let cell: &RefCell<HashMap<alloc::string::String, core::option::Option<Export>>> =
                 instance.global_exports.borrow();
-            let map: &mut HashMap<std::string::String, core::option::Option<Export>> =
+            let map: &mut HashMap<alloc::string::String, core::option::Option<Export>> =
                 &mut cell.borrow_mut();
             match map.entry(field.to_string()) {
                 Vacant(entry) => {

wasmtime-runtime/src/jit_int.rs

@@ -2,8 +2,9 @@
 //! the __jit_debug_register_code() and __jit_debug_descriptor to register
 //! or unregister generated object images with debuggers.
 
-use std::boxed::Box;
-use std::ptr;
+use alloc::boxed::Box;
+use alloc::vec::Vec;
+use core::ptr;
 
 #[repr(C)]
 struct JITCodeEntry {
@@ -40,7 +41,7 @@ extern "C" fn __jit_debug_register_code() {
     // Hack to not allow inlining even when Rust wants to do it in release mode.
     let x = 3;
     unsafe {
-        std::ptr::read_volatile(&x);
+        core::ptr::read_volatile(&x);
     }
 }
 

wasmtime-runtime/src/lib.rs

@@ -21,6 +21,7 @@
         clippy::use_self
     )
 )]
+#![cfg_attr(not(feature = "std"), no_std)]
 
 #[macro_use]
 extern crate lazy_static;
@@ -28,6 +29,7 @@ extern crate lazy_static;
 extern crate memoffset;
 #[macro_use]
 extern crate failure_derive;
+extern crate alloc;
 
 mod export;
 mod imports;
@@ -59,5 +61,15 @@ 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");

wasmtime-runtime/src/memory.rs

@@ -4,8 +4,8 @@
 
 use crate::mmap::Mmap;
 use crate::vmcontext::VMMemoryDefinition;
-use std::convert::TryFrom;
-use std::string::String;
+use alloc::string::String;
+use core::convert::TryFrom;
 use wasmtime_environ::{MemoryPlan, MemoryStyle, WASM_MAX_PAGES, WASM_PAGE_SIZE};
 
 /// A linear memory instance.

wasmtime-runtime/src/mmap.rs

@@ -1,14 +1,14 @@
 //! Low-level abstraction for allocating and managing zero-filled pages
 //! of memory.
 
+use alloc::string::{String, ToString};
+use alloc::vec::Vec;
 use core::ptr;
 use core::slice;
 use errno;
 #[cfg(not(target_os = "windows"))]
 use libc;
 use region;
-use std::string::{String, ToString};
-use std::vec::Vec;
 
 /// Round `size` up to the nearest multiple of `page_size`.
 fn round_up_to_page_size(size: usize, page_size: usize) -> usize {

wasmtime-runtime/src/sig_registry.rs

@@ -2,9 +2,9 @@
 //! signature checking.
 
 use crate::vmcontext::VMSharedSignatureIndex;
+use crate::{hash_map, HashMap};
+use core::convert::TryFrom;
 use cranelift_codegen::ir;
-use std::collections::{hash_map, HashMap};
-use std::convert::TryFrom;
 
 /// WebAssembly requires that the caller and callee signatures in an indirect
 /// call must match. To implement this efficiently, keep a registry of all
@@ -29,11 +29,11 @@ impl SignatureRegistry {
         match self.signature_hash.entry(sig.clone()) {
             hash_map::Entry::Occupied(entry) => *entry.get(),
             hash_map::Entry::Vacant(entry) => {
-                // Keep `signature_hash` len under 2**32 -- VMSharedSignatureIndex::new(std::u32::MAX)
+                // Keep `signature_hash` len under 2**32 -- VMSharedSignatureIndex::new(core::u32::MAX)
                 // is reserved for VMSharedSignatureIndex::default().
                 debug_assert!(
-                    len < std::u32::MAX as usize,
-                    "Invariant check: signature_hash.len() < std::u32::MAX"
+                    len < core::u32::MAX as usize,
+                    "Invariant check: signature_hash.len() < core::u32::MAX"
                 );
                 let sig_id = VMSharedSignatureIndex::new(u32::try_from(len).unwrap());
                 entry.insert(sig_id);

wasmtime-runtime/src/signalhandlers.rs

@@ -5,9 +5,9 @@
 #![allow(non_snake_case)]
 
 use crate::vmcontext::VMContext;
+use crate::RwLock;
 use core::borrow::{Borrow, BorrowMut};
 use core::cell::Cell;
-use std::sync::RwLock;
 
 #[derive(Default)]
 struct TrapContext {

wasmtime-runtime/src/table.rs

@@ -3,9 +3,9 @@
 //! `Table` is to WebAssembly tables what `LinearMemory` is to WebAssembly linear memories.
 
 use crate::vmcontext::{VMCallerCheckedAnyfunc, VMTableDefinition};
+use alloc::vec::Vec;
+use core::convert::{TryFrom, TryInto};
 use cranelift_wasm::TableElementType;
-use std::convert::{TryFrom, TryInto};
-use std::vec::Vec;
 use wasmtime_environ::{TablePlan, TableStyle};
 
 /// A table instance.
@@ -25,7 +25,7 @@ impl Table {
             }
         };
         assert!(
-            plan.table.minimum <= std::u32::MAX,
+            plan.table.minimum <= core::u32::MAX,
             "Invariant check: vec.len() <= u32::MAX"
         );
         match plan.style {
@@ -60,7 +60,7 @@ impl Table {
             }
         };
         assert!(
-            new_len <= std::u32::MAX,
+            new_len <= core::u32::MAX,
             "Invariant check: vec.len() <= u32::MAX"
         );
         self.vec.resize(

wasmtime-runtime/src/trap_registry.rs

@@ -1,7 +1,7 @@
+use crate::HashMap;
+use crate::{RwLock, RwLockReadGuard, RwLockWriteGuard};
 use cranelift_codegen::ir;
 use lazy_static::lazy_static;
-use std::collections::HashMap;
-use std::sync::{RwLock, RwLockReadGuard, RwLockWriteGuard};
 
 lazy_static! {
     static ref REGISTRY: RwLock<TrapRegistry> = RwLock::new(TrapRegistry::default());

wasmtime-runtime/src/traphandlers.rs

@@ -4,10 +4,10 @@
 use crate::trap_registry::get_trap_registry;
 use crate::trap_registry::TrapDescription;
 use crate::vmcontext::{VMContext, VMFunctionBody};
+use alloc::string::{String, ToString};
 use core::cell::Cell;
 use core::ptr;
 use cranelift_codegen::ir;
-use std::string::String;
 
 extern "C" {
     fn WasmtimeCallTrampoline(