Helpers to manage start section

res/cases/v1/start_mut.wast

@@ -0,0 +1,24 @@
+(module
+ (type $0 (func (param i32) (result i32)))
+ (type $1 (func (result i32)))
+ (type $2 (func))
+ (import "env" "memoryBase" (global $gimport$0 i32))
+ (import "env" "memory" (memory $0 256))
+ (import "env" "table" (table 0 anyfunc))
+ (import "env" "tableBase" (global $gimport$4 i32))
+ (import "env" "_puts" (func $fimport$1 (param i32) (result i32)))
+ (global $global$0 (mut i32) (i32.const 0))
+ (global $global$1 (mut i32) (i32.const 0))
+ (global $global$2 i32 (i32.const 0))
+ (data (i32.const 13) "hello, world!")
+ (export "_main" (func $0))
+ (start $0)
+ (func $0 (type $2)
+  (drop
+   (call $fimport$1
+    (get_global $gimport$0)
+   )
+  )
+ )
+)
+

src/elements/module.rs

@@ -241,6 +241,32 @@ impl Module {
 		None
 	}
 
+	/// Changes the module's start section.
+	pub fn set_start_section(&mut self, new_start : u32) {
+		for section in self.sections_mut() {
+			if let &mut Section::Start(_sect) = section {
+                *section = Section::Start(new_start);
+                return
+            }
+		}
+        self.sections_mut().push(Section::Start(new_start));
+	}
+
+    /// Removes the module's start section.
+    pub fn clear_start_section(&mut self) {
+        let sections = self.sections_mut();
+        let mut rmidx = sections.len();
+        for (index, section) in sections.iter_mut().enumerate() {
+            if let Section::Start(_sect) = section {
+                rmidx = index;
+                break;
+            }
+        }
+        if rmidx < sections.len() {
+            sections.remove(rmidx);
+        }
+    }
+
 	/// Functions signatures section reference, if any.
 	/// NOTE: name section is not parsed by default so `names_section` could return None even if name section exists.
 	/// Call `parse_names` to parse name section
@@ -713,4 +739,14 @@ mod integration_tests {
 		let module = deserialize_file("./res/cases/v1/two-mems.wasm").expect("failed to deserialize");
 		assert_eq!(module.memory_space(), 2);
 	}
+
+    #[test]
+    fn mut_start() {
+        let mut module = deserialize_file("./res/cases/v1/start_mut.wasm").expect("failed to deserialize");
+        assert_eq!(module.start_section().expect("Did not find any start section"), 1);
+        module.set_start_section(0);
+        assert_eq!(module.start_section().expect("Did not find any start section"), 0);
+        module.clear_start_section();
+        assert_eq!(None, module.start_section());
+    }
 }