Update no_std support.

This `no_std` support isn't complete though, as some dependencies
don't support it.

lib/runtime/src/instance.rs

@@ -13,16 +13,17 @@ use crate::vmcontext::{
     VMGlobalImport, VMMemoryDefinition, VMMemoryImport, VMSharedSignatureIndex, VMTableDefinition,
     VMTableImport,
 };
+use core::slice;
+use core::{mem, ptr};
 use cranelift_entity::EntityRef;
 use cranelift_entity::{BoxedSlice, PrimaryMap};
 use cranelift_wasm::{
     DefinedFuncIndex, DefinedGlobalIndex, DefinedMemoryIndex, DefinedTableIndex, FuncIndex,
     GlobalIndex, GlobalInit, MemoryIndex, SignatureIndex, TableIndex,
 };
+use std::borrow::ToOwned;
 use std::rc::Rc;
-use std::slice;
 use std::string::String;
-use std::{mem, ptr};
 use wasmtime_environ::{DataInitializer, Module, TableElements, VMOffsets};
 
 fn signature_id(

lib/runtime/src/lib.rs

@@ -21,15 +21,24 @@
         clippy::use_self
     )
 )]
-#![cfg_attr(not(feature = "std"), no_std)]
+#![no_std]
 #![cfg_attr(not(feature = "std"), feature(alloc))]
 
+#[cfg(not(feature = "std"))]
+#[macro_use]
+extern crate alloc as std;
+#[cfg(feature = "std")]
+#[macro_use]
+extern crate std;
+
+#[cfg(not(feature = "std"))]
+use hashmap_core::{map as hash_map, HashMap};
+#[cfg(feature = "std")]
+use std::collections::{hash_map, HashMap};
+
 use errno;
 use region;
 
-#[cfg(not(feature = "std"))]
-#[macro_use]
-extern crate alloc;
 #[macro_use]
 extern crate lazy_static;
 use libc;
@@ -66,10 +75,3 @@ pub use crate::vmcontext::{
     VMContext, VMFunctionBody, VMFunctionImport, VMGlobalDefinition, VMGlobalImport,
     VMMemoryDefinition, VMMemoryImport, VMSharedSignatureIndex, VMTableDefinition, VMTableImport,
 };
-
-#[cfg(not(feature = "std"))]
-mod std {
-    pub use alloc::{string, vec};
-    pub use core::*;
-    pub use core::{i32, str, u32};
-}

lib/runtime/src/mmap.rs

@@ -1,12 +1,13 @@
 //! Low-level abstraction for allocating and managing zero-filled pages
 //! of memory.
 
+use core::ptr;
+use core::slice;
 use errno;
 use libc;
 use region;
-use std::ptr;
-use std::slice;
-use std::string::String;
+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 {

lib/runtime/src/sig_registry.rs

@@ -1,10 +1,10 @@
 //! Implement a registry of function signatures, for fast indirect call
 //! signature checking.
 
+use super::{hash_map, HashMap};
 use crate::vmcontext::VMSharedSignatureIndex;
 use cast;
 use cranelift_codegen::ir;
-use std::collections::{hash_map, HashMap};
 
 /// WebAssembly requires that the caller and callee signatures in an indirect
 /// call must match. To implement this efficiently, keep a registry of all

lib/runtime/src/signalhandlers.rs

@@ -5,8 +5,8 @@
 #![allow(non_snake_case)]
 
 use crate::vmcontext::VMContext;
-use std::borrow::{Borrow, BorrowMut};
-use std::cell::RefCell;
+use core::borrow::{Borrow, BorrowMut};
+use core::cell::RefCell;
 use std::sync::RwLock;
 
 include!(concat!(env!("OUT_DIR"), "/signalhandlers.rs"));

lib/runtime/src/table.rs

@@ -4,6 +4,7 @@
 
 use crate::vmcontext::{VMCallerCheckedAnyfunc, VMTableDefinition};
 use cranelift_wasm::TableElementType;
+use std::vec::Vec;
 use wasmtime_environ::{TablePlan, TableStyle};
 
 /// A table instance.

lib/runtime/src/traphandlers.rs

@@ -3,11 +3,12 @@
 
 use crate::signalhandlers::jmp_buf;
 use crate::vmcontext::{VMContext, VMFunctionBody};
+use core::cell::{Cell, RefCell};
+use core::mem;
+use core::ptr;
 use libc::c_int;
-use std::cell::{Cell, RefCell};
-use std::mem;
-use std::ptr;
 use std::string::String;
+use std::vec::Vec;
 
 // Currently we uset setjmp/longjmp to unwind out of a signal handler
 // and back to the point where WebAssembly was called (via `call_wasm`).

lib/runtime/src/vmcontext.rs

@@ -2,7 +2,7 @@
 //! fields that compiled wasm code accesses directly.
 
 use crate::instance::InstanceContents;
-use std::{ptr, u32};
+use core::{ptr, u32};
 
 /// An imported function.
 #[derive(Debug, Copy, Clone)]
@@ -18,7 +18,7 @@ pub struct VMFunctionImport {
 #[cfg(test)]
 mod test_vmfunction_import {
     use super::VMFunctionImport;
-    use std::mem::size_of;
+    use core::mem::size_of;
     use wasmtime_environ::{Module, VMOffsets};
 
     #[test]
@@ -50,7 +50,7 @@ pub struct VMFunctionBody(u8);
 #[cfg(test)]
 mod test_vmfunction_body {
     use super::VMFunctionBody;
-    use std::mem::size_of;
+    use core::mem::size_of;
 
     #[test]
     fn check_vmfunction_body_offsets() {
@@ -73,7 +73,7 @@ pub struct VMTableImport {
 #[cfg(test)]
 mod test_vmtable_import {
     use super::VMTableImport;
-    use std::mem::size_of;
+    use core::mem::size_of;
     use wasmtime_environ::{Module, VMOffsets};
 
     #[test]
@@ -110,7 +110,7 @@ pub struct VMMemoryImport {
 #[cfg(test)]
 mod test_vmmemory_import {
     use super::VMMemoryImport;
-    use std::mem::size_of;
+    use core::mem::size_of;
     use wasmtime_environ::{Module, VMOffsets};
 
     #[test]
@@ -144,7 +144,7 @@ pub struct VMGlobalImport {
 #[cfg(test)]
 mod test_vmglobal_import {
     use super::VMGlobalImport;
-    use std::mem::size_of;
+    use core::mem::size_of;
     use wasmtime_environ::{Module, VMOffsets};
 
     #[test]
@@ -178,7 +178,7 @@ pub struct VMMemoryDefinition {
 #[cfg(test)]
 mod test_vmmemory_definition {
     use super::VMMemoryDefinition;
-    use std::mem::size_of;
+    use core::mem::size_of;
     use wasmtime_environ::{Module, VMOffsets};
 
     #[test]
@@ -221,7 +221,7 @@ pub struct VMTableDefinition {
 #[cfg(test)]
 mod test_vmtable_definition {
     use super::VMTableDefinition;
-    use std::mem::size_of;
+    use core::mem::size_of;
     use wasmtime_environ::{Module, VMOffsets};
 
     #[test]
@@ -257,7 +257,7 @@ pub struct VMGlobalDefinition {
 #[cfg(test)]
 mod test_vmglobal_definition {
     use super::VMGlobalDefinition;
-    use std::mem::{align_of, size_of};
+    use core::mem::{align_of, size_of};
     use wasmtime_environ::{Module, VMOffsets};
 
     #[test]
@@ -391,7 +391,7 @@ pub struct VMSharedSignatureIndex(u32);
 #[cfg(test)]
 mod test_vmshared_signature_index {
     use super::VMSharedSignatureIndex;
-    use std::mem::size_of;
+    use core::mem::size_of;
     use wasmtime_environ::{Module, VMOffsets};
 
     #[test]
@@ -427,7 +427,7 @@ pub struct VMCallerCheckedAnyfunc {
 #[cfg(test)]
 mod test_vmcaller_checked_anyfunc {
     use super::VMCallerCheckedAnyfunc;
-    use std::mem::size_of;
+    use core::mem::size_of;
     use wasmtime_environ::{Module, VMOffsets};
 
     #[test]