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-api/src/trampoline/code_memory.rs

@@ -1,10 +1,10 @@
 //! Memory management for executable code.
 // Copy of wasmtime's wasmtime-jit/src/code_memory.rs
 
+use alloc::string::String;
+use alloc::vec::Vec;
 use core::{cmp, mem};
 use region;
-use std::string::String;
-use std::vec::Vec;
 use wasmtime_runtime::{Mmap, VMFunctionBody};
 
 /// Memory manager for executable code.

wasmtime-api/src/trampoline/create_handle.rs

@@ -7,10 +7,13 @@ use failure::Error;
 use wasmtime_environ::Module;
 use wasmtime_runtime::{Imports, InstanceHandle, VMFunctionBody};
 
-use std::any::Any;
-use std::cell::{RefCell, RefMut};
-use std::collections::{HashMap, HashSet};
-use std::rc::Rc;
+use crate::{HashMap, HashSet};
+use alloc::boxed::Box;
+use alloc::rc::Rc;
+use alloc::string::String;
+use alloc::vec::Vec;
+use core::any::Any;
+use core::cell::{RefCell, RefMut};
 
 use crate::runtime::Store;
 

wasmtime-api/src/trampoline/func.rs

@@ -14,8 +14,11 @@ use failure::Error;
 use wasmtime_environ::{Export, Module};
 use wasmtime_runtime::{InstanceHandle, VMContext, VMFunctionBody};
 
+use alloc::boxed::Box;
+use alloc::rc::Rc;
+use alloc::string::ToString;
+use alloc::vec::Vec;
 use core::cmp;
-use std::rc::Rc;
 
 use crate::{Callable, FuncType, Store, Trap, Val};
 

wasmtime-api/src/trampoline/global.rs

@@ -1,3 +1,4 @@
+use alloc::boxed::Box;
 use cranelift_entity::PrimaryMap;
 use failure::Error;
 use wasmtime_environ::Module;

wasmtime-api/src/trampoline/memory.rs

@@ -1,3 +1,5 @@
+use alloc::boxed::Box;
+use alloc::string::ToString;
 use cranelift_entity::PrimaryMap;
 use failure::Error;
 use wasmtime_environ::Module;
@@ -13,7 +15,7 @@ pub fn create_handle_with_memory(memory: &MemoryType) -> Result<InstanceHandle,
 
     let memory = cranelift_wasm::Memory {
         minimum: memory.limits().min(),
-        maximum: if memory.limits().max() == std::u32::MAX {
+        maximum: if memory.limits().max() == core::u32::MAX {
             None
         } else {
             Some(memory.limits().max())

wasmtime-api/src/trampoline/mod.rs

@@ -8,8 +8,8 @@ mod memory;
 mod table;
 
 use crate::r#ref::HostRef;
+use alloc::rc::Rc;
 use failure::Error;
-use std::rc::Rc;
 
 use self::func::create_handle_with_function;
 use self::global::create_global;

wasmtime-api/src/trampoline/table.rs

@@ -1,3 +1,5 @@
+use alloc::boxed::Box;
+use alloc::string::ToString;
 use cranelift_entity::PrimaryMap;
 use cranelift_wasm::TableElementType;
 use failure::Error;
@@ -12,7 +14,7 @@ pub fn create_handle_with_table(table: &TableType) -> Result<InstanceHandle, Err
 
     let table = cranelift_wasm::Table {
         minimum: table.limits().min(),
-        maximum: if table.limits().max() == std::u32::MAX {
+        maximum: if table.limits().max() == core::u32::MAX {
             None
         } else {
             Some(table.limits().max())