fix no_std building

Cargo.toml

@@ -15,9 +15,8 @@ wasmi-validation = { version = "0.2", path = "validation", default-features = fa
 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-traits = "0.2.8"
-libc = "0.2.58"
+num-rational = { version = "0.2.2", default-features = false }
+num-traits = { version = "0.2.8", default-features = false }
 
 [dev-dependencies]
 assert_matches = "1.1"
@@ -31,6 +30,7 @@ std = [
     "parity-wasm/std",
     "wasmi-validation/std",
     "num-rational/std",
+    "num-rational/bigint-std",
     "num-traits/std"
 ]
 # Enable for no_std support

src/nan_preserving_float.rs

@@ -1,5 +1,8 @@
 #![allow(missing_docs)]
 
+#[cfg(not(feature = "std"))]
+use libm::{F32Ext, F64Ext};
+
 use core::cmp::{Ordering, PartialEq, PartialOrd};
 use core::ops::{Add, Div, Mul, Neg, Rem, Sub};
 

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)