src/main/java/de/hsrm/compiler/Klang/visitors/GenASM.java

@@ -71,7 +71,7 @@ public class GenASM implements Visitor<Void> {
   private int lCount = 0;
   private int currentFunctionStartLabel = 0;
   private long bytesToClearFromTheStack = 0;
-  private Parameter[] currentFunctionParams;
+  private FunctionDefinition currentFunctionDef;
 
   public GenASM(String mainName, Map<String, StructDefinition> structs) {
     this.mainName = mainName;
@@ -543,9 +543,23 @@ public class GenASM implements Visitor<Void> {
 
   @Override
   public Void visit(Block e) {
-    for (var statement : e.statementsOrFunctionCalls) {
-      statement.welcome(this);
+    for (var statementOrFunctionCall : e.statementsOrFunctionCalls) {
+      statementOrFunctionCall.welcome(this);
     }
+
+    // It's possible (and allowed -> void functions) that there is no return statement
+    // in the outermost block of a function body. In this case, no
+    // direct descendant of Block will be a return statement.
+    // This means we have to generate an implicit return, otherwise
+    // the code would fall through to the next function below :D
+    // We also have to clean up the stack which is the ReturnStatement's job.
+
+    // Check if we have to generate an implicit return
+    var lastStatementOrFunctionCall = e.statementsOrFunctionCalls[e.statementsOrFunctionCalls.length - 1];
+    if (currentFunctionDef.block == e && !(lastStatementOrFunctionCall instanceof ReturnStatement)) {
+      visit(new ReturnStatement());
+    }
+
     return null;
   }
 
@@ -558,9 +572,11 @@ public class GenASM implements Visitor<Void> {
       e.name = "main_by_user";
     }
 
+    // Remember the current function definition so everyone below us knows where they belong to.
+    currentFunctionDef = e;
+
     var lblStart = ++lCount;
     currentFunctionStartLabel = lblStart;
-    currentFunctionParams = e.parameters;
     asm.functionHead(e.name);
     asm.push("q", "%rbp");
     asm.mov("q", "%rsp", "%rbp");
@@ -675,10 +691,10 @@ public class GenASM implements Visitor<Void> {
 
       // push args into local var locations, last arg is on top of the stack
       for (int i = e.arguments.length - 1; i >= 0; i--) {
-        asm.pop("q", this.env.get(this.currentFunctionParams[i].name) + "(%rbp)");
+        asm.pop("q", env.get(currentFunctionDef.parameters[i].name) + "(%rbp)");
       }
 
-      asm.jmp(this.currentFunctionStartLabel);
+      asm.jmp(currentFunctionStartLabel);
       return null;
     }