Make GC work.

src/patches/README

@@ -0,0 +1,7 @@
+Patches live here for submodules that should remain as pristine as possible.
+This will allow us to unconditionally update them, then apply necessary
+patches as needed.
+
+* mozjs-stack-bounds.diff:
+    add a public API to overwrite the engine's computed stack bounds for
+    GC scanning.

src/patches/mozjs-stack-bounds.diff

@@ -0,0 +1,72 @@
+diff --git a/js/src/jsapi.cpp b/js/src/jsapi.cpp
+index 5571fc0..df2fabd 100644
+--- a/js/src/jsapi.cpp
++++ b/js/src/jsapi.cpp
+@@ -735,6 +735,7 @@ JSRuntime::JSRuntime()
+ #endif
+     selfHostedGlobal_(NULL),
+     nativeStackBase(0),
++    nativeStackEnd(0),
+     nativeStackQuota(0),
+     interpreterFrames(NULL),
+     cxCallback(NULL),
+@@ -7084,6 +7085,13 @@ JS_SetRuntimeThread(JSRuntime *rt)
+ #endif
+ }
+ 
++extern JS_PUBLIC_API(void)
++JS_SetNativeStackBounds(JSRuntime *rt, uintptr_t stackBase, uintptr_t stackEnd)
++{
++    rt->nativeStackBase = stackBase;
++    rt->nativeStackEnd = stackEnd;
++}
++
+ extern JS_NEVER_INLINE JS_PUBLIC_API(void)
+ JS_AbortIfWrongThread(JSRuntime *rt)
+ {
+diff --git a/js/src/jsapi.h b/js/src/jsapi.h
+index c8ab0f0..0edb722 100644
+--- a/js/src/jsapi.h
++++ b/js/src/jsapi.h
+@@ -6248,6 +6248,9 @@ JS_ClearRuntimeThread(JSRuntime *rt);
+ extern JS_PUBLIC_API(void)
+ JS_SetRuntimeThread(JSRuntime *rt);
+ 
++extern JS_PUBLIC_API(void)
++JS_SetNativeStackBounds(JSRuntime *rt, uintptr_t stackBase, uintptr_t stackEnd);
++
+ #ifdef __cplusplus
+ JS_END_EXTERN_C
+ 
+diff --git a/js/src/jscntxt.h b/js/src/jscntxt.h
+index 0bb6d1c..32e016e 100644
+--- a/js/src/jscntxt.h
++++ b/js/src/jscntxt.h
+@@ -439,6 +439,9 @@ struct JSRuntime : js::RuntimeFriendFields
+     /* Base address of the native stack for the current thread. */
+     uintptr_t           nativeStackBase;
+ 
++    /* Base address of the native stack for the current thread. */
++    uintptr_t           nativeStackEnd;
++
+     /* The native stack size limit that runtime should not exceed. */
+     size_t              nativeStackQuota;
+ 
+diff --git a/js/src/jsgc.cpp b/js/src/jsgc.cpp
+index f5cbc62..eae29da 100644
+--- a/js/src/jsgc.cpp
++++ b/js/src/jsgc.cpp
+@@ -1177,9 +1177,11 @@ MarkConservativeStackRoots(JSTracer *trc, bool useSavedRoots)
+     uintptr_t *stackMin, *stackEnd;
+ #if JS_STACK_GROWTH_DIRECTION > 0
+     stackMin = rt->nativeStackBase;
+-    stackEnd = cgcd->nativeStackTop;
++    stackEnd = rt->nativeStackEnd ? reinterpret_cast<uintptr_t*>(rt->nativeStackEnd)
++                                 : cgcd->nativeStackTop;
+ #else
+-    stackMin = cgcd->nativeStackTop + 1;
++    stackMin = rt->nativeStackEnd ? reinterpret_cast<uintptr_t*>(rt->nativeStackEnd)
++                                 : cgcd->nativeStackTop + 1;
+     stackEnd = reinterpret_cast<uintptr_t *>(rt->nativeStackBase);
+ #endif
+ 

src/servo/dom/bindings/element.rs

@@ -32,10 +32,10 @@ extern fn finalize(_fop: *JSFreeOp, obj: *JSObject) {
     }
 }
 
-pub extern fn trace(tracer: *JSTracer, obj: *JSObject) {
+pub extern fn trace(tracer: *mut JSTracer, obj: *JSObject) {
     let node = unsafe { unwrap(obj) };
 
-    fn trace_node(tracer: *JSTracer, node: Option<AbstractNode>, name: &str) {
+    fn trace_node(tracer: *mut JSTracer, node: Option<AbstractNode>, name: &str) {
         if node.is_none() {
             return;
         }
@@ -45,7 +45,12 @@ pub extern fn trace(tracer: *JSTracer, obj: *JSObject) {
         let wrapper = cache.get_wrapper();
         assert!(wrapper.is_not_null());
         unsafe {
-            JS_CallTracer(tracer, wrapper, JSTRACE_OBJECT as u32);
+            (*tracer).debugPrinter = ptr::null();
+            (*tracer).debugPrintIndex = -1;
+            do str::as_c_str(name) |name| {
+                (*tracer).debugPrintArg = name as *libc::c_void;
+                JS_CallTracer(cast::transmute(tracer), wrapper, JSTRACE_OBJECT as u32);
+            }
         }
     }
     error!("tracing %?:", obj as uint);

src/servo/dom/bindings/utils.rs

@@ -290,10 +290,8 @@ static DOM_PROXY_OBJECT_SLOT: uint = js::JSSLOT_PROXY_PRIVATE as uint;
 // changes.
 static DOM_PROTO_INSTANCE_CLASS_SLOT: u32 = 0;
 
-// All DOM globals must have a slot at DOM_PROTOTYPE_SLOT. We have to
-// start at 1 past JSCLASS_GLOBAL_SLOT_COUNT because XPConnect uses
-// that one.
-pub static DOM_PROTOTYPE_SLOT: u32 = js::JSCLASS_GLOBAL_SLOT_COUNT + 1;
+// All DOM globals must have a slot at DOM_PROTOTYPE_SLOT.
+pub static DOM_PROTOTYPE_SLOT: u32 = js::JSCLASS_GLOBAL_SLOT_COUNT;
 
 // NOTE: This is baked into the Ion JIT as 0 in codegen for LGetDOMProperty and
 // LSetDOMProperty. Those constants need to be changed accordingly if this value
@@ -580,6 +578,10 @@ pub impl WrapperCache {
         self.wrapper = wrapper;
     }
 
+    fn get_rootable(&self) -> **JSObject {
+        return ptr::addr_of(&self.wrapper);
+    }
+
     fn new() -> WrapperCache {
         WrapperCache {
             wrapper: ptr::null()

src/servo/dom/bindings/window.rs

@@ -16,7 +16,7 @@ use js::crust::{JS_PropertyStub, JS_StrictPropertyStub};
 use js::global::jsval_to_rust_str;
 use js::glue::bindgen::*;
 use js::glue::bindgen::RUST_JSVAL_TO_INT;
-use js::jsapi::bindgen::{JS_DefineFunctions};
+use js::jsapi::bindgen::{JS_DefineFunctions, JS_GC, JS_GetRuntime};
 use js::jsapi::bindgen::{JS_GetReservedSlot, JS_SetReservedSlot};
 use js::jsapi::bindgen::{JS_ValueToString};
 use js::jsapi::{JSContext, JSVal, JSObject, JSBool, JSFreeOp, JSFunctionSpec};
@@ -31,12 +31,15 @@ extern fn alert(cx: *JSContext, argc: c_uint, vp: *JSVal) -> JSBool {
     assert!(argc == 1);
     // Abstract this pattern and use it in debug, too?
     let jsstr = JS_ValueToString(cx, *ptr::offset(argv, 0));
+    if jsstr.is_null() {
+        return 0;
+    }
     
     (*unwrap(JS_THIS_OBJECT(cx, vp))).payload.alert(jsval_to_rust_str(cx, jsstr));
 
     JS_SET_RVAL(cx, vp, JSVAL_NULL);
+    return 1;
   }
-  1_i32
 }
 
 extern fn setTimeout(cx: *JSContext, argc: c_uint, vp: *JSVal) -> JSBool {
@@ -63,6 +66,14 @@ extern fn close(cx: *JSContext, _argc: c_uint, vp: *JSVal) -> JSBool {
     }
 }
 
+extern fn gc(cx: *JSContext, _argc: c_uint, _vp: *JSVal) -> JSBool {
+    unsafe {
+        let runtime = JS_GetRuntime(cx);
+        JS_GC(runtime);
+        return 1;
+    }
+}
+
 unsafe fn unwrap(obj: *JSObject) -> *rust_box<Window> {
     let val = JS_GetReservedSlot(obj, 0);
     cast::reinterpret_cast(&RUST_JSVAL_TO_PRIVATE(val))
@@ -99,7 +110,14 @@ pub fn init(compartment: @mut Compartment) {
         JSFunctionSpec {
             name: compartment.add_name(~"close"),
             call: JSNativeWrapper { op: close, info: null() },
-            nargs: 2,
+            nargs: 0,
+            flags: 0,
+            selfHostedName: null()
+        },
+        JSFunctionSpec {
+            name: compartment.add_name(~"_trigger_gc"),
+            call: JSNativeWrapper { op: gc, info: null() },
+            nargs: 0,
             flags: 0,
             selfHostedName: null()
         },

src/servo/dom/document.rs

@@ -27,9 +27,9 @@ pub fn Document(root: AbstractNode,
     };
     let compartment = global_content().compartment.get();
     do root.with_imm_node |node| {
-        let wrapper = node.wrapper.get_wrapper();
-        assert!(wrapper.is_not_null());
-        unsafe { JS_AddObjectRoot(compartment.cx.ptr, ptr::addr_of(&wrapper)); }
+        assert!(node.wrapper.get_wrapper().is_not_null());
+        let rootable = node.wrapper.get_rootable();
+        unsafe { JS_AddObjectRoot(compartment.cx.ptr, rootable); }
     }
     document::create(compartment, doc);
     doc
@@ -40,9 +40,9 @@ impl Drop for Document {
     fn finalize(&self) {
         let compartment = global_content().compartment.get();
         do self.root.with_imm_node |node| {
-            let wrapper = node.wrapper.get_wrapper();
-            assert!(wrapper.is_not_null());
-            unsafe { JS_RemoveObjectRoot(compartment.cx.ptr, ptr::addr_of(&wrapper)); }
+            assert!(node.wrapper.get_wrapper().is_not_null());
+            let rootable = node.wrapper.get_rootable();
+            unsafe { JS_RemoveObjectRoot(compartment.cx.ptr, rootable); }
         }
     }
 }

src/servo/dom/element.rs

@@ -20,13 +20,6 @@ pub struct Element {
     attrs: ~[Attr],
 }
 
-#[unsafe_destructor]
-impl Drop for Element {
-    fn finalize(&self) {
-        fail!(~"uh oh");
-    }
-}
-
 #[deriving(Eq)]
 pub enum ElementTypeId {
     HTMLAnchorElementTypeId,

src/test/test_hammer_layout.css

@@ -1,3 +1,3 @@
-div #styled {
+#styled {
   color: red;
 }

src/test/test_hammer_layout.html

@@ -4,6 +4,6 @@
 <script src="test_hammer_layout.js"></script>
 </head>
 <body>
-<div id="styled">This text is unstyled.</div>
+<div id="">This text is unstyled.</div>
 </body>
 </html>

src/test/test_hammer_layout.js

@@ -1,17 +1,6 @@
-window.setTimeout(function() {
-  //var divs = document.getElementsByTagName("div");
-//  divs[0].setAttribute('id', 'styled');
-  function print_tree(n) {
-    window.alert(n.nodeType);
-    //window.alert(n.tagName);
-    n = n.firstChild;
-    while (n) {
-      print_tree(n);
-      n = n.nextSibling;
-    }
-  }
-  print_tree(document.documentElement);
-//window.alert(document.documentElement.tagName);
-//window.alert(document.documentElement.firstChild.nodeType);
-//window.alert(document.documentElement.firstChild.firstChild.nodeType);
-}, 200);
+var divs = document.getElementsByTagName("div");
+var div = divs[0];
+for (var i = 0; i < 1000000; i++) {
+  div.setAttribute('id', 'styled');
+}
+