Fix GC interface and collect automatically (AssemblyScript#848)

Author: dcodeIO

std/assembly/gc.ts

@@ -0,0 +1,13 @@
+/// <reference path="./rt/index.d.ts" />
+
+/** Garbage collector interface. */
+export namespace gc {
+
+  /** Can be set to `false` to disable automatic collection. Defaults to `true`. */
+  export var auto: bool = true;
+
+  /** Performs a full garbage collection cycle. */
+  export function collect(): void {
+    __collect();
+  }
+}

std/assembly/index.d.ts

@@ -1032,16 +1032,12 @@ declare namespace memory {
   export function compare(vl: usize, vr: usize, n: usize): i32;
 }
 
-/** Garbage collector operations. */
+/** Garbage collector interface. */
 declare namespace gc {
-  /** Whether the garbage collector interface is implemented. */
-  export const implemented: bool;
+  /** Can be set to `false` to disable automatic collection. Defaults to `true`. */
+  export var auto: bool;
   /** Performs a full garbage collection cycle. */
   export function collect(): void;
-  /** Retains a reference, making sure that it doesn't become collected. */
-  export function retain(ref: usize): void;
-  /** Releases a reference, allowing it to become collected. */
-  export function release(ref: usize): void;
 }
 
 /** Table operations. */

std/assembly/rt/tlsf.ts

@@ -477,14 +477,31 @@ export function initializeRoot(): void {
   ROOT = root;
 }
 
+// @ts-ignore: decorator
+@lazy
+var collectLock: bool = false;
+
 /** Allocates a block of the specified size. */
 export function allocateBlock(root: Root, size: usize): Block {
+  if (DEBUG) assert(!collectLock); // must not allocate while collecting
   var payloadSize = prepareSize(size);
   var block = searchBlock(root, payloadSize);
   if (!block) {
-    growMemory(root, payloadSize);
-    block = <Block>searchBlock(root, payloadSize);
-    if (DEBUG) assert(block); // must be found now
+    if (gc.auto) {
+      if (DEBUG) collectLock = true;
+      __collect();
+      if (DEBUG) collectLock = false;
+      block = searchBlock(root, payloadSize);
+      if (!block) {
+        growMemory(root, payloadSize);
+        block = <Block>searchBlock(root, payloadSize);
+        if (DEBUG) assert(block); // must be found now
+      }
+    } else {
+      growMemory(root, payloadSize);
+      block = <Block>searchBlock(root, payloadSize);
+      if (DEBUG) assert(block); // must be found now
+    }
   }
   if (DEBUG) assert((block.mmInfo & ~TAGS_MASK) >= payloadSize); // must fit
   block.gcInfo = 0; // RC=0