Auto merge of #18549 - nnethercote:fix-enclosing-crash, r=heycam

Fix a panic in Stylo memory reporting.

`MallocSizeOfOps::enclosing_size_of_op` is an `Option<>` type, and the panic in
question is caused by not providing a value in a case where it's needed for
measuring a HashSet.

HashMaps and HashSets are common enough that it makes sense to make
`enclosing_size_of_op` non-optional, which this patch does.

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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [ ] These changes fix #__ (github issue number if applicable).

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- [ ] There are tests for these changes OR
- [X] These changes do not require tests because tests are on the Gecko side.

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components/malloc_size_of/lib.rs

@@ -82,9 +82,8 @@ pub struct MallocSizeOfOps {
     /// A function that returns the size of a heap allocation.
     size_of_op: VoidPtrToSizeFn,
 
-    /// Like `size_of_op`, but can take an interior pointer. Optional, because
-    /// many places don't need it.
-    enclosing_size_of_op: Option<VoidPtrToSizeFn>,
+    /// Like `size_of_op`, but can take an interior pointer.
+    enclosing_size_of_op: VoidPtrToSizeFn,
 
     /// Check if a pointer has been seen before, and remember it for next time.
     /// Useful when measuring `Rc`s and `Arc`s. Optional, because many places
@@ -93,8 +92,7 @@ pub struct MallocSizeOfOps {
 }
 
 impl MallocSizeOfOps {
-    pub fn new(size_of: VoidPtrToSizeFn,
-               malloc_enclosing_size_of: Option<VoidPtrToSizeFn>,
+    pub fn new(size_of: VoidPtrToSizeFn, malloc_enclosing_size_of: VoidPtrToSizeFn,
                have_seen_ptr: Option<Box<VoidPtrToBoolFnMut>>) -> Self {
         MallocSizeOfOps {
             size_of_op: size_of,
@@ -129,8 +127,7 @@ impl MallocSizeOfOps {
     /// Call `enclosing_size_of_op` on `ptr`, which must not be empty.
     pub unsafe fn malloc_enclosing_size_of<T>(&self, ptr: *const T) -> usize {
         assert!(!MallocSizeOfOps::is_empty(ptr));
-        let enclosing_size_of_op = self.enclosing_size_of_op.expect("missing enclosing_size_of_op");
-        enclosing_size_of_op(ptr as *const c_void)
+        (self.enclosing_size_of_op)(ptr as *const c_void)
     }
 
     /// Call `have_seen_ptr_op` on `ptr`.

components/style/gecko/generated/bindings.rs

@@ -1898,7 +1898,10 @@ extern "C" {
     pub fn Servo_Element_ClearData(node: RawGeckoElementBorrowed);
 }
 extern "C" {
-    pub fn Servo_Element_SizeOfExcludingThisAndCVs(arg1: MallocSizeOf,
+    pub fn Servo_Element_SizeOfExcludingThisAndCVs(malloc_size_of:
+                                                       MallocSizeOf,
+                                                   malloc_enclosing_size_of:
+                                                       MallocSizeOf,
                                                    seen_ptrs: *mut SeenPtrs,
                                                    node:
                                                        RawGeckoElementBorrowed)
@@ -1964,6 +1967,8 @@ extern "C" {
 }
 extern "C" {
     pub fn Servo_StyleSheet_SizeOfIncludingThis(malloc_size_of: MallocSizeOf,
+                                                malloc_enclosing_size_of:
+                                                    MallocSizeOf,
                                                 sheet:
                                                     RawServoStyleSheetContentsBorrowed)
      -> usize;