fix no_std building

* Avoid temporary allocation when push locals during function invocation.

* Extend value stack for all locals at once.

.travis.yml

@@ -11,8 +11,6 @@ matrix:
   - rust: stable
   - rust: stable
     env: TARGET=armv7-unknown-linux-gnueabihf
-  allow_failures:
-  - rust: nightly
 
 install:
 - if [ "$TRAVIS_RUST_VERSION" == "nightly" ]; then rustup target add wasm32-unknown-unknown; fi
@@ -42,7 +40,17 @@ after_success: |
   ghp-import -n target/doc &&
   git push -fq https://${GH_TOKEN}@github.com/${TRAVIS_REPO_SLUG}.git gh-pages
 
-cache: cargo
+cache:
+  # Don't use `cache: cargo` since it adds the `target` directory and that can be huge.
+  # Saving and loading this directory dwarfes actual compilation and test times. But what is more
+  # important, is that travis timeouts the build since the job doesn't produce any output for more
+  # than 10 minutes.
+  #
+  # So we just cache ~/.cargo directory
+  directories:
+    - /home/travis/.cargo
 before_cache:
   # Travis can't cache files that are not readable by "others"
   - chmod -R a+r $HOME/.cargo
+  # According to the Travis CI docs for building Rust project this is done by,
+  - rm -rf /home/travis/.cargo/registry

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "wasmi"
-version = "0.5.0"
+version = "0.5.1"
 authors = ["Nikolay Volf <nikvolf@gmail.com>", "Svyatoslav Nikolsky <svyatonik@yandex.ru>", "Sergey Pepyakin <s.pepyakin@gmail.com>"]
 license = "MIT/Apache-2.0"
 readme = "README.md"
@@ -11,18 +11,17 @@ keywords = ["wasm", "webassembly", "bytecode", "interpreter"]
 exclude = [ "/res/*", "/tests/*", "/fuzz/*", "/benches/*" ]
 
 [dependencies]
-wasmi-validation = { version = "0.1", path = "validation", default-features = false }
+wasmi-validation = { version = "0.2", path = "validation", default-features = false }
-parity-wasm = { version = "0.31", default-features = false }
+parity-wasm = { version = "0.40.1", default-features = false }
 memory_units = "0.3.0"
 libm = { version = "0.1.2", optional = true }
-num-rational = "0.2.2"
+num-rational = { version = "0.2.2", default-features = false }
-num-traits = "0.2.8"
+num-traits = { version = "0.2.8", default-features = false }
-libc = "0.2.58"
 
 [dev-dependencies]
 assert_matches = "1.1"
 rand = "0.4.2"
-wabt = "0.6"
+wabt = "0.9"
 
 [features]
 default = ["std"]
@@ -31,10 +30,13 @@ std = [
     "parity-wasm/std",
     "wasmi-validation/std",
     "num-rational/std",
+    "num-rational/bigint-std",
     "num-traits/std"
 ]
 # Enable for no_std support
 core = [
+    # `core` doesn't support vec_memory
+    "vec_memory",
     "wasmi-validation/core",
     "libm"
 ]

README.md

@@ -26,8 +26,8 @@ This crate supports `no_std` environments.
 Enable the `core` feature and disable default features:
 ```toml
 [dependencies]
-parity-wasm = {
+wasmi = {
-	version = "0.31",
+	version = "*",
 	default-features = false,
 	features = "core"
 }

benches/Cargo.toml

@@ -6,7 +6,7 @@ authors = ["Sergey Pepyakin <s.pepyakin@gmail.com>"]
 [dependencies]
 wasmi = { path = ".." }
 assert_matches = "1.2"
-wabt = "0.6"
+wabt = "0.9"
 
 [profile.bench]
 debug = true

benches/src/lib.rs

@@ -13,7 +13,7 @@ use wasmi::{ImportsBuilder, Module, ModuleInstance, NopExternals, RuntimeValue};
 use test::Bencher;
 
 // Load a module from a file.
-fn load_from_file(filename: &str) -> Result<Module, Box<error::Error>> {
+fn load_from_file(filename: &str) -> Result<Module, Box<dyn error::Error>> {
 	use std::io::prelude::*;
 	let mut file = File::open(filename)?;
 	let mut buf = Vec::new();

benches/wasm-kernel/src/lib.rs

@@ -33,7 +33,7 @@ pub extern "C" fn prepare_tiny_keccak() -> *const TinyKeccakTestData {
 }
 
 #[no_mangle]
-pub extern "C" fn bench_tiny_keccak(test_data: *const TinyKeccakTestData) {
+pub extern "C" fn bench_tiny_keccak(test_data: *mut TinyKeccakTestData) {
 	unsafe {
 		let mut keccak = Keccak::new_keccak256();
 		keccak.update((*test_data).data);

fuzz/Cargo.toml

@@ -10,7 +10,7 @@ cargo-fuzz = true
 
 [dependencies]
 wasmi = { path = ".." }
-wabt = "0.6.0"
+wabt = "0.9"
 wasmparser = "0.14.1"
 tempdir = "0.3.6"
 

hfuzz/Cargo.toml

@@ -7,4 +7,4 @@ authors = ["Sergey Pepyakin <s.pepyakin@gmail.com>"]
 honggfuzz = "=0.5.9" # Strict equal since hfuzz requires dep and cmd versions to match.
 wasmi = { path = ".." }
 tempdir = "0.3.6"
-wabt = "0.6.0"
+wabt = "0.9"

src/func.rs

@@ -1,6 +1,8 @@
-#[allow(unused_imports)]
+use alloc::{
-use alloc::prelude::v1::*;
+    borrow::Cow,
-use alloc::rc::{Rc, Weak};
+    rc::{Rc, Weak},
+    vec::Vec,
+};
 use core::fmt;
 use host::Externals;
 use isa;
@@ -194,12 +196,13 @@ impl FuncInstance {
     /// [`resume_execution`]: struct.FuncInvocation.html#method.resume_execution
     pub fn invoke_resumable<'args>(
         func: &FuncRef,
-        args: &'args [RuntimeValue],
+        args: impl Into<Cow<'args, [RuntimeValue]>>,
     ) -> Result<FuncInvocation<'args>, Trap> {
+        let args = args.into();
         check_function_args(func.signature(), &args)?;
         match *func.as_internal() {
             FuncInstanceInternal::Internal { .. } => {
-                let interpreter = Interpreter::new(func, args, None)?;
+                let interpreter = Interpreter::new(func, &*args, None)?;
                 Ok(FuncInvocation {
                     kind: FuncInvocationKind::Internal(interpreter),
                 })
@@ -256,7 +259,7 @@ pub struct FuncInvocation<'args> {
 enum FuncInvocationKind<'args> {
     Internal(Interpreter),
     Host {
-        args: &'args [RuntimeValue],
+        args: Cow<'args, [RuntimeValue]>,
         host_func_index: usize,
         finished: bool,
     },
@@ -303,7 +306,7 @@ impl<'args> FuncInvocation<'args> {
                     return Err(ResumableError::AlreadyStarted);
                 }
                 *finished = true;
-                Ok(externals.invoke_index(*host_func_index, args.clone().into())?)
+                Ok(externals.invoke_index(*host_func_index, args.as_ref().into())?)
             }
         }
     }

src/host.rs

@@ -114,11 +114,11 @@ pub trait HostError: 'static + ::core::fmt::Display + ::core::fmt::Debug + Send
     }
 }
 
-impl HostError {
+impl dyn HostError {
     /// Attempt to downcast this `HostError` to a concrete type by reference.
     pub fn downcast_ref<T: HostError>(&self) -> Option<&T> {
         if self.__private_get_type_id__() == TypeId::of::<T>() {
-            unsafe { Some(&*(self as *const HostError as *const T)) }
+            unsafe { Some(&*(self as *const dyn HostError as *const T)) }
         } else {
             None
         }
@@ -128,7 +128,7 @@ impl HostError {
     /// reference.
     pub fn downcast_mut<T: HostError>(&mut self) -> Option<&mut T> {
         if self.__private_get_type_id__() == TypeId::of::<T>() {
-            unsafe { Some(&mut *(self as *mut HostError as *mut T)) }
+            unsafe { Some(&mut *(self as *mut dyn HostError as *mut T)) }
         } else {
             None
         }
@@ -257,5 +257,5 @@ mod tests {
     }
 
     // Tests that `HostError` trait is object safe.
-    fn _host_error_is_object_safe(_: &HostError) {}
+    fn _host_error_is_object_safe(_: &dyn HostError) {}
 }

src/imports.rs

@@ -1,7 +1,4 @@
-#[allow(unused_imports)]
+use alloc::{collections::BTreeMap, string::String};
-use alloc::prelude::v1::*;
-
-use alloc::collections::BTreeMap;
 
 use func::FuncRef;
 use global::GlobalRef;
@@ -103,7 +100,7 @@ pub trait ImportResolver {
 /// [`ImportResolver`]: trait.ImportResolver.html
 /// [`ModuleImportResolver`]: trait.ModuleImportResolver.html
 pub struct ImportsBuilder<'a> {
-    modules: BTreeMap<String, &'a ModuleImportResolver>,
+    modules: BTreeMap<String, &'a dyn ModuleImportResolver>,
 }
 
 impl<'a> Default for ImportsBuilder<'a> {
@@ -124,7 +121,7 @@ impl<'a> ImportsBuilder<'a> {
     pub fn with_resolver<N: Into<String>>(
         mut self,
         name: N,
-        resolver: &'a ModuleImportResolver,
+        resolver: &'a dyn ModuleImportResolver,
     ) -> Self {
         self.modules.insert(name.into(), resolver);
         self
@@ -133,11 +130,15 @@ impl<'a> ImportsBuilder<'a> {
     /// Register an resolver by a name.
     ///
     /// Mutable borrowed version.
-    pub fn push_resolver<N: Into<String>>(&mut self, name: N, resolver: &'a ModuleImportResolver) {
+    pub fn push_resolver<N: Into<String>>(
+        &mut self,
+        name: N,
+        resolver: &'a dyn ModuleImportResolver,
+    ) {
         self.modules.insert(name.into(), resolver);
     }
 
-    fn resolver(&self, name: &str) -> Option<&ModuleImportResolver> {
+    fn resolver(&self, name: &str) -> Option<&dyn ModuleImportResolver> {
         self.modules.get(name).cloned()
     }
 }

src/isa.rs

@@ -67,8 +67,7 @@
 //! - Reserved immediates are ignored for `call_indirect`, `current_memory`, `grow_memory`.
 //!
 
-#[allow(unused_imports)]
+use alloc::vec::Vec;
-use alloc::prelude::v1::*;
 
 /// Should we keep a value before "discarding" a stack frame?
 ///

src/lib.rs

@@ -96,8 +96,6 @@
 
 #![warn(missing_docs)]
 #![cfg_attr(not(feature = "std"), no_std)]
-//// alloc is required in no_std
-#![cfg_attr(not(feature = "std"), feature(alloc, alloc_prelude))]
 
 #[cfg(not(feature = "std"))]
 #[macro_use]
@@ -119,8 +117,11 @@ extern crate parity_wasm;
 
 extern crate wasmi_validation as validation;
 
-#[allow(unused_imports)]
+use alloc::{
-use alloc::prelude::v1::*;
+    boxed::Box,
+    string::{String, ToString},
+    vec::Vec,
+};
 use core::fmt;
 #[cfg(feature = "std")]
 use std::error;
@@ -239,7 +240,7 @@ pub enum TrapKind {
     /// Typically returned from an implementation of [`Externals`].
     ///
     /// [`Externals`]: trait.Externals.html
-    Host(Box<host::HostError>),
+    Host(Box<dyn host::HostError>),
 }
 
 impl TrapKind {
@@ -273,7 +274,7 @@ pub enum Error {
     /// Trap.
     Trap(Trap),
     /// Custom embedder error.
-    Host(Box<host::HostError>),
+    Host(Box<dyn host::HostError>),
 }
 
 impl Error {
@@ -285,7 +286,7 @@ impl Error {
     /// [`Host`]: enum.Error.html#variant.Host
     /// [`Trap`]: enum.Error.html#variant.Trap
     /// [`TrapKind::Host`]: enum.TrapKind.html#variant.Host
-    pub fn as_host_error(&self) -> Option<&host::HostError> {
+    pub fn as_host_error(&self) -> Option<&dyn host::HostError> {
         match *self {
             Error::Host(ref host_err) => Some(&**host_err),
             Error::Trap(ref trap) => match *trap.kind() {

src/memory/mod.rs

@@ -1,6 +1,4 @@
-#[allow(unused_imports)]
+use alloc::{rc::Rc, string::ToString, vec::Vec};
-use alloc::prelude::v1::*;
-use alloc::rc::Rc;
 use core::{
     cell::{Cell, RefCell},
     cmp, fmt,

src/memory/vec_bytebuf.rs

@@ -1,6 +1,6 @@
 //! An implementation of `ByteBuf` based on a plain `Vec`.
 
-use alloc::prelude::v1::*;
+use alloc::vec::Vec;
 
 pub struct ByteBuf {
     buf: Vec<u8>,

src/module.rs

@@ -1,6 +1,9 @@
-#[allow(unused_imports)]
+use alloc::{
-use alloc::prelude::v1::*;
+    borrow::ToOwned,
-use alloc::rc::Rc;
+    rc::Rc,
+    string::{String, ToString},
+    vec::Vec,
+};
 use core::cell::RefCell;
 use core::fmt;
 use Trap;
@@ -418,7 +421,11 @@ impl ModuleInstance {
             .map(|es| es.entries())
             .unwrap_or(&[])
         {
-            let offset_val = match eval_init_expr(element_segment.offset(), &module_ref) {
+            let offset = element_segment
+                .offset()
+                .as_ref()
+                .expect("passive segments are rejected due to validation");
+            let offset_val = match eval_init_expr(offset, &module_ref) {
                 RuntimeValue::I32(v) => v as u32,
                 _ => panic!("Due to validation elem segment offset should evaluate to i32"),
             };
@@ -447,7 +454,11 @@ impl ModuleInstance {
         }
 
         for data_segment in module.data_section().map(|ds| ds.entries()).unwrap_or(&[]) {
-            let offset_val = match eval_init_expr(data_segment.offset(), &module_ref) {
+            let offset = data_segment
+                .offset()
+                .as_ref()
+                .expect("passive segments are rejected due to validation");
+            let offset_val = match eval_init_expr(offset, &module_ref) {
                 RuntimeValue::I32(v) => v as u32,
                 _ => panic!("Due to validation data segment offset should evaluate to i32"),
             };

src/prepare/compile.rs

@@ -1,5 +1,4 @@
-#[allow(unused_imports)]
+use alloc::{string::String, vec::Vec};
-use alloc::prelude::v1::*;
 
 use parity_wasm::elements::{BlockType, FuncBody, Instruction};
 
@@ -252,13 +251,14 @@ impl Compiler {
                 );
                 self.sink.emit_br_nez(target);
             }
-            BrTable(ref table, default) => {
+            BrTable(ref br_table_data) => {
                 // At this point, the condition value is at the top of the stack.
                 // But at the point of actual jump the condition will already be
                 // popped off.
                 let value_stack_height = context.value_stack.len().saturating_sub(1);
 
-                let targets = table
+                let targets = br_table_data
+                    .table
                     .iter()
                     .map(|depth| {
                         require_target(
@@ -270,7 +270,7 @@ impl Compiler {
                     })
                     .collect::<Result<Vec<_>, _>>();
                 let default_target = require_target(
-                    default,
+                    br_table_data.default,
                     value_stack_height,
                     &context.frame_stack,
                     &self.label_stack,

src/prepare/mod.rs

@@ -1,5 +1,4 @@
-#[allow(unused_imports)]
+use alloc::vec::Vec;
-use alloc::prelude::v1::*;
 
 use crate::{
     isa,

src/runner.rs

@@ -1,5 +1,4 @@
-#[allow(unused_imports)]
+use alloc::{boxed::Box, vec::Vec};
-use alloc::prelude::v1::*;
 use core::fmt;
 use core::ops;
 use core::{u32, usize};
@@ -1290,14 +1289,8 @@ impl FunctionContext {
         debug_assert!(!self.is_initialized);
 
         let num_locals = locals.iter().map(|l| l.count() as usize).sum();
-        let locals = vec![Default::default(); num_locals];
 
-        // TODO: Replace with extend.
+        value_stack.extend(num_locals)?;
-        for local in locals {
-            value_stack
-                .push(local)
-                .map_err(|_| TrapKind::StackOverflow)?;
-        }
 
         self.is_initialized = true;
         Ok(())
@@ -1443,6 +1436,18 @@ impl ValueStack {
         Ok(())
     }
 
+    fn extend(&mut self, len: usize) -> Result<(), TrapKind> {
+        let cells = self
+            .buf
+            .get_mut(self.sp..self.sp + len)
+            .ok_or_else(|| TrapKind::StackOverflow)?;
+        for cell in cells {
+            *cell = Default::default();
+        }
+        self.sp += len;
+        Ok(())
+    }
+
     #[inline]
     fn len(&self) -> usize {
         self.sp

src/table.rs

@@ -1,6 +1,4 @@
-#[allow(unused_imports)]
+use alloc::{rc::Rc, vec::Vec};
-use alloc::prelude::v1::*;
-use alloc::rc::Rc;
 use core::cell::RefCell;
 use core::fmt;
 use core::u32;

src/tests/host.rs

@@ -285,7 +285,7 @@ fn resume_call_host_func() {
     let export = instance.export_by_name("test").unwrap();
     let func_instance = export.as_func().unwrap();
 
-    let mut invocation = FuncInstance::invoke_resumable(&func_instance, &[]).unwrap();
+    let mut invocation = FuncInstance::invoke_resumable(&func_instance, &[][..]).unwrap();
     let result = invocation.start_execution(&mut env);
     match result {
         Err(ResumableError::Trap(_)) => {}
@@ -330,7 +330,7 @@ fn resume_call_host_func_type_mismatch() {
         let export = instance.export_by_name("test").unwrap();
         let func_instance = export.as_func().unwrap();
 
-        let mut invocation = FuncInstance::invoke_resumable(&func_instance, &[]).unwrap();
+        let mut invocation = FuncInstance::invoke_resumable(&func_instance, &[][..]).unwrap();
         let result = invocation.start_execution(&mut env);
         match result {
             Err(ResumableError::Trap(_)) => {}

src/value.rs

@@ -368,6 +368,7 @@ impl WrapInto<F32> for F64 {
 macro_rules! impl_try_truncate_into {
     (@primitive $from: ident, $into: ident, $to_primitive:path) => {
         impl TryTruncateInto<$into, TrapKind> for $from {
+            #[cfg(feature = "std")]
             fn try_truncate_into(self) -> Result<$into, TrapKind> {
                 // Casting from a float to an integer will round the float towards zero
                 num_rational::BigRational::from_float(self)
@@ -375,6 +376,23 @@ macro_rules! impl_try_truncate_into {
                     .and_then(|val| $to_primitive(&val))
                     .ok_or(TrapKind::InvalidConversionToInt)
             }
+            #[cfg(not(feature = "std"))]
+            fn try_truncate_into(self) -> Result<$into, TrapKind> {
+                // Casting from a float to an integer will round the float towards zero
+                // NOTE: currently this will cause Undefined Behavior if the rounded value cannot be represented by the
+                // target integer type. This includes Inf and NaN. This is a bug and will be fixed.
+                if self.is_nan() || self.is_infinite() {
+                    return Err(TrapKind::InvalidConversionToInt);
+                }
+
+                // range check
+                let result = self as $into;
+                if result as $from != self.trunc() {
+                    return Err(TrapKind::InvalidConversionToInt);
+                }
+
+                Ok(self as $into)
+            }
         }
     };
     (@wrapped $from:ident, $intermediate:ident, $into:ident) => {
@@ -819,15 +837,6 @@ impl_integer!(u32);
 impl_integer!(i64);
 impl_integer!(u64);
 
-// Use std float functions in std environment.
-// And libm's implementation in no_std
-#[cfg(feature = "std")]
-macro_rules! call_math {
-    ($op:ident, $e:expr, $fXX:ident, $FXXExt:ident) => {
-        $fXX::$op($e)
-    };
-}
-#[cfg(not(feature = "std"))]
 macro_rules! call_math {
     ($op:ident, $e:expr, $fXX:ident, $FXXExt:ident) => {
         ::libm::$FXXExt::$op($e)

tests/spec/run.rs

@@ -18,6 +18,7 @@ fn spec_to_runtime_value(val: Value<u32, u64>) -> RuntimeValue {
         Value::I64(v) => RuntimeValue::I64(v),
         Value::F32(v) => RuntimeValue::F32(v.into()),
         Value::F64(v) => RuntimeValue::F64(v.into()),
+        Value::V128(_) => panic!("v128 is not supported"),
     }
 }
 

validation/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "wasmi-validation"
-version = "0.1.0"
+version = "0.2.0"
 authors = ["Parity Technologies <admin@parity.io>"]
 edition = "2018"
 license = "MIT/Apache-2.0"
@@ -8,7 +8,7 @@ repository = "https://github.com/paritytech/wasmi"
 description = "Wasm code validator"
 
 [dependencies]
-parity-wasm = { version = "0.31", default-features = false }
+parity-wasm = { version = "0.40.1", default-features = false }
 
 [dev-dependencies]
 assert_matches = "1.1"

validation/src/context.rs

@@ -1,6 +1,5 @@
 use crate::Error;
-#[allow(unused_imports)]
+use alloc::vec::Vec;
-use alloc::prelude::v1::*;
 use parity_wasm::elements::{
     BlockType, FunctionType, GlobalType, MemoryType, TableType, ValueType,
 };

validation/src/func.rs

@@ -1,6 +1,3 @@
-#[allow(unused_imports)]
-use alloc::prelude::v1::*;
-
 use crate::{
     context::ModuleContext, stack::StackWithLimit, util::Locals, Error, FuncValidator,
     DEFAULT_MEMORY_INDEX, DEFAULT_TABLE_INDEX,
@@ -269,8 +266,8 @@ impl<'a> FunctionValidationContext<'a> {
             BrIf(depth) => {
                 self.validate_br_if(depth)?;
             }
-            BrTable(ref table, default) => {
+            BrTable(ref br_table_data) => {
-                self.validate_br_table(table, default)?;
+                self.validate_br_table(&*br_table_data.table, br_table_data.default)?;
                 make_top_frame_polymorphic(&mut self.value_stack, &mut self.frame_stack);
             }
             Return => {

validation/src/lib.rs

@@ -2,8 +2,6 @@
 // #![warn(missing_docs)]
 
 #![cfg_attr(not(feature = "std"), no_std)]
-//// alloc is required in no_std
-#![cfg_attr(not(feature = "std"), feature(alloc, alloc_prelude))]
 
 #[cfg(not(feature = "std"))]
 #[macro_use]
@@ -21,8 +19,7 @@ pub const DEFAULT_TABLE_INDEX: u32 = 0;
 /// Maximal number of pages that a wasm instance supports.
 pub const LINEAR_MEMORY_MAX_PAGES: u32 = 65536;
 
-#[allow(unused_imports)]
+use alloc::{string::String, vec::Vec};
-use alloc::prelude::v1::*;
 use core::fmt;
 #[cfg(feature = "std")]
 use std::error;
@@ -322,7 +319,11 @@ pub fn validate_module<V: Validator>(module: &Module) -> Result<V::Output, Error
     if let Some(data_section) = module.data_section() {
         for data_segment in data_section.entries() {
             context.require_memory(data_segment.index())?;
-            let init_ty = expr_const_type(data_segment.offset(), context.globals())?;
+            let offset = data_segment
+                .offset()
+                .as_ref()
+                .ok_or_else(|| Error("passive memory segments are not supported".into()))?;
+            let init_ty = expr_const_type(&offset, context.globals())?;
             if init_ty != ValueType::I32 {
                 return Err(Error("segment offset should return I32".into()));
             }
@@ -333,8 +334,11 @@ pub fn validate_module<V: Validator>(module: &Module) -> Result<V::Output, Error
     if let Some(element_section) = module.elements_section() {
         for element_segment in element_section.entries() {
             context.require_table(element_segment.index())?;
-
+            let offset = element_segment
-            let init_ty = expr_const_type(element_segment.offset(), context.globals())?;
+                .offset()
+                .as_ref()
+                .ok_or_else(|| Error("passive element segments are not supported".into()))?;
+            let init_ty = expr_const_type(&offset, context.globals())?;
             if init_ty != ValueType::I32 {
                 return Err(Error("segment offset should return I32".into()));
             }

validation/src/stack.rs

@@ -1,5 +1,4 @@
-#[allow(unused_imports)]
+use alloc::{string::String, vec::Vec};
-use alloc::prelude::v1::*;
 
 use core::fmt;
 #[cfg(feature = "std")]

validation/src/util.rs

@@ -1,6 +1,5 @@
 use crate::Error;
-#[allow(unused_imports)]
+use alloc::string::String;
-use alloc::prelude::v1::*;
 use parity_wasm::elements::{Local, ValueType};
 
 #[cfg(test)]