Validate descriptor max on creating new table or memory (#186)

lib/runtime-core/src/error.rs

@@ -266,6 +266,7 @@ impl std::fmt::Display for CallError {
 pub enum CreationError {
     UnableToCreateMemory,
     UnableToCreateTable,
+    InvalidDescriptor(String),
 }
 
 impl PartialEq for CreationError {
@@ -279,6 +280,11 @@ impl std::fmt::Display for CreationError {
         match self {
             CreationError::UnableToCreateMemory => write!(f, "Unable to Create Memory"),
             CreationError::UnableToCreateTable => write!(f, "Unable to Create Table"),
+            CreationError::InvalidDescriptor(msg) => write!(
+                f,
+                "Unable to create because the supplied descriptor is invalid: \"{}\"",
+                msg
+            ),
         }
     }
 }

lib/runtime-core/src/memory/mod.rs

@@ -63,6 +63,15 @@ impl Memory {
     /// # }
     /// ```
     pub fn new(desc: MemoryDescriptor) -> Result<Self, CreationError> {
+        if let Some(max) = desc.maximum {
+            if max < desc.minimum {
+                return Err(CreationError::InvalidDescriptor(
+                    "Max number of memory pages is less than the minimum number of pages"
+                        .to_string(),
+                ));
+            }
+        }
+
         let variant = if !desc.shared {
             MemoryVariant::Unshared(UnsharedMemory::new(desc)?)
         } else {

lib/runtime-core/src/table/mod.rs

@@ -50,6 +50,14 @@ impl Table {
     /// # }
     /// ```
     pub fn new(desc: TableDescriptor) -> Result<Self, CreationError> {
+        if let Some(max) = desc.maximum {
+            if max < desc.minimum {
+                return Err(CreationError::InvalidDescriptor(
+                    "Max table size is less than the minimum size".to_string(),
+                ));
+            }
+        }
+
         let mut local = vm::LocalTable {
             base: ptr::null_mut(),
             count: 0,