Throw error if allocating non-positive length for array/slice/buffere…

…d channel

src/tests/test.ts

@@ -2073,7 +2073,7 @@ go func() {
 go func() {
     s.Down();
     x = x + 1;
-    fmt.Println("x in Thread 2 is " + x); // this should be 2 because goroutine in T1 sleeps
+    fmt.Println("x in Thread 2 is " + x); // this should be 2
 }();
 
 go func() {

src/vm/oogavm-compiler.ts

@@ -1041,14 +1041,6 @@ function compile(component, ce) {
     return compileComp[component.tag](component, ce);
 }
 
-// FIXME: The problem with the current impl is that our PC does not start
-//        at the first line, but really the main function (and the init function)
-//        So we need a way for the machine to know where it must start
-//        The termination condition for the program should also be when main ends
-//        So, we should compile the entire thing, find where main ends and put DONE there.
-//        To handle the main function entry point, perhaps the first line of the bytecode
-//        can be reserved to indicating the start location for the PC.
-//        But this seems like a band-aid fix.
 export function compile_program(program) {
     initializeBuiltinTable();
     wc = 0;

src/vm/oogavm-heap.ts

@@ -550,6 +550,9 @@ function isString(address: number): boolean {
 // ********************************
 
 export function allocateArray(numValues: number): number {
+    if (numValues <= 0) {
+        throw new RuntimeError('Cannot allocate array with non-positive length!');
+    }
     return allocate(Tag.ARRAY, numValues + headerSize);
 }
 
@@ -598,6 +601,9 @@ export function getArrayValueAtIndex(arrayAddress: number, idx: number): any {
 // A slice is a resizable array.
 // 3rd word is for current number of elements inside.
 export function allocateSlice(len: number, initialCapacity: number): number {
+    if (len <= 0) {
+        throw new RuntimeError('Cannot allocate slice with non-positive length!');
+    }
     if (len > initialCapacity) {
         throw new RuntimeError('Cannot allocate slice with len more than capacity');
     }
@@ -718,6 +724,9 @@ export function getSliceLength(address: number): number {
 // then have to worry about node pointer manipulation at the moment
 
 export function allocateBufferedChannel(capacity: number): number {
+    if (capacity <= 0) {
+        throw new RuntimeError('Cannot allocate buffered channel with non-positive capacity!');
+    }
     const address = allocate(Tag.BUFFERED, capacity + headerSize + 1);
     // starts with 0 size
     heap.setUint32((address + headerSize) * wordSize, 0);