Teach stack limiter to handle start fn

src/stack_height/mod.rs

@@ -25,11 +25,12 @@
 //! Because stack height is increased prior the call few problems arises:
 //!
 //! - Stack height isn't increased upon an entry to the first function, i.e. exported function.
+//! - Start function is executed externally (similar to exported functions).
 //! - It is statically unknown what function will be invoked in an indirect call.
 //!
 //! The solution for this problems is to generate a intermediate functions, called 'thunks', which
 //! will increase before and decrease the stack height after the call to original function, and
-//! then make exported function and table entries to point to a corresponding thunks.
+//! then make exported function and table entries, start section to point to a corresponding thunks.
 //!
 //! # Stack cost
 //!

src/stack_height/thunk.rs

@@ -35,6 +35,8 @@ pub(crate) fn generate_thunks(
 			.elements_section()
 			.map(|es| es.entries())
 			.unwrap_or(&[]);
+		let start_func_idx = module
+			.start_section();
 
 		let exported_func_indicies = exports.iter().filter_map(|entry| match *entry.internal() {
 			Internal::Function(ref function_idx) => Some(*function_idx),
@@ -48,7 +50,7 @@ pub(crate) fn generate_thunks(
 		// Replacement map is at least export section size.
 		let mut replacement_map: Map<u32, Thunk> = Map::new();
 
-		for func_idx in exported_func_indicies.chain(table_func_indicies) {
+		for func_idx in exported_func_indicies.chain(table_func_indicies).chain(start_func_idx.into_iter()) {
 			let callee_stack_cost = ctx.stack_cost(func_idx).ok_or_else(|| {
 				Error(format!("function with idx {} isn't found", func_idx))
 			})?;
@@ -154,6 +156,9 @@ pub(crate) fn generate_thunks(
 					}
 				}
 			}
+			elements::Section::Start(ref mut start_idx) => {
+				fixup(start_idx)
+			}
 			_ => {}
 		}
 	}