fix(wasm): correct exported func index

xtuc · xtuc · commit 42379540f837 · 2018-05-07T09:49:14.000+02:00
diff --git a/lib/wasm/WebAssemblyGenerator.js b/lib/wasm/WebAssemblyGenerator.js
@@ -19,6 +19,8 @@ function compose(...fns) {
 
 // Utility functions
 const isGlobalImport = moduleImport => moduleImport.descr.type === "GlobalType";
+const isFuncImport = moduleImport =>
+	moduleImport.descr.type === "FuncImportDescr";
 const initFuncId = t.identifier("__webpack_init__");
 
 // TODO replace with @callback
@@ -50,8 +52,8 @@ function getStartFuncIndex(ast) {
 	let startAtFuncIndex;
 
 	t.traverse(ast, {
-		Start(path) {
-			startAtFuncIndex = path.node.index;
+		Start({ node }) {
+			startAtFuncIndex = node.index;
 		}
 	});
 
@@ -78,6 +80,20 @@ function getImportedGlobals(ast) {
 	return importedGlobals;
 }
 
+function getCountImportedFunc(ast) {
+	let count = 0;
+
+	t.traverse(ast, {
+		ModuleImport({ node }) {
+			if (isFuncImport(node) === true) {
+				count++;
+			}
+		}
+	});
+
+	return count;
+}
+
 /**
  * Get next type index
  *
@@ -97,17 +113,24 @@ function getNextTypeIndex(ast) {
 /**
  * Get next func index
  *
+ * The Func section metadata provide informations for implemented funcs
+ * in order to have the correct index we shift the index by number of external
+ * functions.
+ *
  * @param {Object} ast - Module's AST
+ * @param {Number} countImportedFunc - number of imported funcs
  * @returns {t.IndexLiteral} - index
  */
-function getNextFuncIndex(ast) {
+function getNextFuncIndex(ast, countImportedFunc) {
 	const funcSectionMetadata = t.getSectionMetadata(ast, "func");
 
 	if (typeof funcSectionMetadata === "undefined") {
-		return t.indexLiteral(0);
+		return t.indexLiteral(0 + countImportedFunc);
 	}
 
-	return t.indexLiteral(funcSectionMetadata.vectorOfSize.value);
+	const vectorOfSize = funcSectionMetadata.vectorOfSize.value;
+
+	return t.indexLiteral(vectorOfSize + countImportedFunc);
 }
 
 /**
@@ -191,14 +214,19 @@ const addInitFunction = ({
 
 	const funcResults = [];
 
+	// Code section
 	const func = t.func(initFuncId, funcParams, funcResults, funcBody);
 
+	// Type section
 	const functype = t.typeInstructionFunc(
 		func.signature.params,
 		func.signature.result
 	);
+
+	// Func section
 	const funcindex = t.indexInFuncSection(nextTypeIndex);
 
+	// Export section
 	const moduleExport = t.moduleExport(initFuncId.value, "Func", nextFuncIndex);
 
 	return add(bin, [func, moduleExport, funcindex, functype]);
@@ -217,8 +245,9 @@ class WebAssemblyGenerator extends Generator {
 
 		const importedGlobals = getImportedGlobals(ast);
 		const funcSectionMetadata = t.getSectionMetadata(ast, "func");
+		const countImportedFunc = getCountImportedFunc(ast);
 		const startAtFuncIndex = getStartFuncIndex(ast);
-		const nextFuncIndex = getNextFuncIndex(ast);
+		const nextFuncIndex = getNextFuncIndex(ast, countImportedFunc);
 		const nextTypeIndex = getNextTypeIndex(ast);
 
 		const transform = compose(
