Auto merge of #12725 - bholley:fix_leaks, r=emilio

stylo: fix leaks, and accept null in Servo_InheritComputedValues

This corresponds to changes in:

https://bugzilla.mozilla.org/show_bug.cgi?id=1291885
and
https://bugzilla.mozilla.org/show_bug.cgi?id=1291891

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components/style/properties/gecko.mako.rs

@@ -100,7 +100,30 @@ impl ComputedValues {
         ComputedValues::inherit_from(parent)
     }
 
-    pub fn initial_values() -> &'static Self { &*INITIAL_GECKO_VALUES }
+    pub fn initial_values() -> &'static Self {
+        unsafe {
+            debug_assert!(!INITIAL_GECKO_VALUES.is_null());
+            &*INITIAL_GECKO_VALUES
+        }
+    }
+
+    pub unsafe fn initialize() {
+        debug_assert!(INITIAL_GECKO_VALUES.is_null());
+        INITIAL_GECKO_VALUES = Box::into_raw(Box::new(ComputedValues {
+            % for style_struct in data.style_structs:
+               ${style_struct.ident}: style_structs::${style_struct.name}::initial(),
+            % endfor
+            custom_properties: None,
+            shareable: true,
+            writing_mode: WritingMode::empty(),
+            root_font_size: longhands::font_size::get_initial_value(),
+        }));
+    }
+
+    pub unsafe fn shutdown() {
+        debug_assert!(!INITIAL_GECKO_VALUES.is_null());
+        let _ = Box::from_raw(INITIAL_GECKO_VALUES);
+    }
 
     #[inline]
     pub fn do_cascade_property<F: FnOnce(&[CascadePropertyFn])>(f: F) {
@@ -236,7 +259,7 @@ def set_gecko_property(ffi_name, expr):
     // In the longer term, Gecko should store currentColor as a computed
     // value, so that we don't need to do this:
     // https://bugzilla.mozilla.org/show_bug.cgi?id=760345
-    unimplemented!();
+    warn!("stylo: mishandling currentColor");
     % endif
 </%def>
 
@@ -1338,17 +1361,7 @@ ${impl_style_struct(style_struct)}
 ${define_ffi_struct_accessor(style_struct)}
 % endfor
 
-lazy_static! {
-    pub static ref INITIAL_GECKO_VALUES: ComputedValues = ComputedValues {
-        % for style_struct in data.style_structs:
-           ${style_struct.ident}: style_structs::${style_struct.name}::initial(),
-        % endfor
-        custom_properties: None,
-        shareable: true,
-        writing_mode: WritingMode::empty(),
-        root_font_size: longhands::font_size::get_initial_value(),
-    };
-}
+static mut INITIAL_GECKO_VALUES: *mut ComputedValues = 0 as *mut ComputedValues;
 
 static CASCADE_PROPERTY: [CascadePropertyFn; ${len(data.longhands)}] = [
     % for property in data.longhands:

ports/geckolib/gecko_bindings/bindings.rs

@@ -375,6 +375,7 @@ extern "C" {
     pub fn Servo_AddRefComputedValues(arg1: *mut ServoComputedValues);
     pub fn Servo_ReleaseComputedValues(arg1: *mut ServoComputedValues);
     pub fn Servo_Initialize();
+    pub fn Servo_Shutdown();
     pub fn Servo_RestyleDocument(doc: *mut RawGeckoDocument,
                                  set: *mut RawServoStyleSet);
     pub fn Servo_RestyleSubtree(node: *mut RawGeckoNode,

ports/geckolib/glue.rs

@@ -76,6 +76,15 @@ pub extern "C" fn Servo_Initialize() -> () {
     //
     // See https://doc.rust-lang.org/log/env_logger/index.html for instructions.
     env_logger::init().unwrap();
+
+    // Allocate our default computed values.
+    unsafe { ComputedValues::initialize(); }
+}
+
+#[no_mangle]
+pub extern "C" fn Servo_Shutdown() -> () {
+    // Destroy our default computed values.
+    unsafe { ComputedValues::shutdown(); }
 }
 
 fn restyle_subtree(node: GeckoNode, raw_data: *mut RawServoStyleSet) {
@@ -355,10 +364,12 @@ pub extern "C" fn Servo_GetComputedValuesForPseudoElement(parent_style: *mut Ser
 pub extern "C" fn Servo_InheritComputedValues(parent_style: *mut ServoComputedValues)
      -> *mut ServoComputedValues {
     type Helpers = ArcHelpers<ServoComputedValues, ComputedValues>;
-    Helpers::with(parent_style, |parent| {
-        let style = ComputedValues::inherit_from(parent);
-        Helpers::from(style)
-    })
+    let style = if parent_style.is_null() {
+        Arc::new(ComputedValues::initial_values().clone())
+    } else {
+        Helpers::with(parent_style, ComputedValues::inherit_from)
+    };
+    Helpers::from(style)
 }
 
 #[no_mangle]

ports/geckolib/wrapper.rs

@@ -53,7 +53,8 @@ use style::selector_impl::ElementExt;
 use style::sink::Push;
 use url::Url;
 
-pub type NonOpaqueStyleData = *mut RefCell<PrivateStyleData>;
+pub type NonOpaqueStyleData = RefCell<PrivateStyleData>;
+pub type NonOpaqueStyleDataPtr = *mut NonOpaqueStyleData;
 
 // Important: We don't currently refcount the DOM, because the wrapper lifetime
 // magic guarantees that our LayoutFoo references won't outlive the root, and
@@ -78,16 +79,16 @@ impl<'ln> GeckoNode<'ln> {
         GeckoNode::from_raw(n as *const RawGeckoNode as *mut RawGeckoNode)
     }
 
-    fn get_node_data(&self) -> NonOpaqueStyleData {
+    fn get_node_data(&self) -> NonOpaqueStyleDataPtr {
         unsafe {
-            Gecko_GetNodeData(self.node) as NonOpaqueStyleData
+            Gecko_GetNodeData(self.node) as NonOpaqueStyleDataPtr
         }
     }
 
     pub fn initialize_data(self) {
         unsafe {
             if self.get_node_data().is_null() {
-                let ptr: NonOpaqueStyleData = Box::into_raw(Box::new(RefCell::new(PrivateStyleData::new())));
+                let ptr: NonOpaqueStyleDataPtr = Box::into_raw(Box::new(RefCell::new(PrivateStyleData::new())));
                 Gecko_SetNodeData(self.node, ptr as *mut ServoNodeData);
             }
         }