libcore: Implement a box annihilator, not called yet

Author: pcwalton

src/libcore/cleanup.rs

@@ -0,0 +1,152 @@
+use libc::{c_char, c_void, intptr_t, uintptr_t};
+use ptr::{mut_null, null, to_unsafe_ptr};
+use repr::BoxRepr;
+use rt::rt_free;
+use sys::TypeDesc;
+use unsafe::transmute;
+
+/**
+ * Runtime structures
+ *
+ * NB: These must match the representation in the C++ runtime.
+ */
+
+type DropGlue = fn(**TypeDesc, *c_void);
+type FreeGlue = fn(**TypeDesc, *c_void);
+
+type TaskID = uintptr_t;
+
+struct StackSegment { priv opaque: () }
+struct Scheduler { priv opaque: () }
+struct SchedulerLoop { priv opaque: () }
+struct Kernel { priv opaque: () }
+struct Env { priv opaque: () }
+struct AllocHeader { priv opaque: () }
+struct MemoryRegion { priv opaque: () }
+
+// XXX: i386
+struct Registers {
+    data: [u64 * 22]
+}
+
+struct Context {
+    regs: Registers,
+    next: *Context,
+    pad: u64
+}
+
+struct BoxedRegion {
+    env: *Env,
+    backing_region: *MemoryRegion,
+    live_allocs: *BoxRepr
+}
+
+struct Task {
+    // Public fields
+    refcount: intptr_t,
+    id: TaskID,
+    ctx: Context,
+    stack_segment: *StackSegment,
+    runtime_sp: uintptr_t,
+    scheduler: *Scheduler,
+    scheduler_loop: *SchedulerLoop,
+
+    // Fields known only to the runtime
+    kernel: *Kernel,
+    name: *c_char,
+    list_index: *i32,
+    rendezvous_ptr: *uintptr_t,
+    boxed_region: BoxedRegion
+}
+
+/*
+ * Box annihilation
+ *
+ * This runs at task death to free all boxes.
+ */
+
+/// Destroys all managed memory (i.e. @ boxes) held by the current task.
+pub unsafe fn annihilate() {
+    let task: *Task = transmute(rustrt::rust_get_task());
+
+    // Pass 1: Make all boxes immortal.
+    let box = (*task).boxed_region.live_allocs;
+    let mut box: *mut BoxRepr = transmute(copy box);
+    assert (*box).prev == null();
+    while box != mut_null() {
+        debug!("making box immortal: %x", box as uint);
+        (*box).ref_count = 0x77777777;
+        box = transmute(copy (*box).next);
+    }
+
+    // Pass 2: Drop all boxes.
+    let box = (*task).boxed_region.live_allocs;
+    let mut box: *mut BoxRepr = transmute(copy box);
+    assert (*box).prev == null();
+    while box != mut_null() {
+        debug!("calling drop glue for box: %x", box as uint);
+        let tydesc: *TypeDesc = transmute(copy (*box).type_desc);
+        let drop_glue: DropGlue = transmute(((*tydesc).drop_glue, 0));
+        drop_glue(to_unsafe_ptr(&tydesc), transmute(&(*box).data));
+
+        box = transmute(copy (*box).next);
+    }
+
+    // Pass 3: Free all boxes.
+    loop {
+        let box = (*task).boxed_region.live_allocs;
+        if box == null() { break; }
+        let mut box: *mut BoxRepr = transmute(copy box);
+        assert (*box).prev == null();
+
+        debug!("freeing box: %x", box as uint);
+        rt_free(transmute(box));
+    }
+}
+
+/// Bindings to the runtime
+extern mod rustrt {
+    #[rust_stack]
+    /*priv*/ fn rust_get_task() -> *c_void;
+}
+
+/*
+ * Tests
+ */
+
+#[cfg(test)]
+mod tests {
+    /*struct Knot {
+        mut a: Option<@Knot>
+    }
+
+    struct Blah {
+        x: int,
+        drop { io::println("Blah!"); }
+    }
+
+    #[test]
+    fn test_box_annihilation() {
+        let knot = @Knot { a: None };
+        knot.a = Some(knot);
+
+        let x = @~"foo";
+
+        let blah = @Blah { x: 3 };
+
+        let f_ref = @mut None;
+        let f = || { util::ignore(f_ref); };
+        *f_ref = Some(f);
+
+        unsafe { annihilate(); }
+
+        unsafe {
+            unsafe::forget(knot);
+            unsafe::forget(x);
+            unsafe::forget(blah);
+            unsafe::forget(f_ref);
+            unsafe::forget(f);
+        }
+    }*/
+}
+

src/libcore/core.rc

@@ -244,6 +244,7 @@ mod unicode;
 mod private;
 mod cmath;
 mod stackwalk;
+mod cleanup;
 
 // Local Variables:
 // mode: rust;

src/libcore/ptr.rs

@@ -9,6 +9,7 @@ export offset;
 export const_offset;
 export mut_offset;
 export null;
+export mut_null;
 export is_null;
 export is_not_null;
 export memcpy;
@@ -98,6 +99,10 @@ unsafe fn position<T>(buf: *T, f: fn(T) -> bool) -> uint {
 #[inline(always)]
 pure fn null<T>() -> *T { unsafe { unsafe::reinterpret_cast(&0u) } }
 
+/// Create an unsafe mutable null pointer
+#[inline(always)]
+pure fn mut_null<T>() -> *mut T { unsafe { unsafe::reinterpret_cast(&0u) } }
+
 /// Returns true if the pointer is equal to the null pointer.
 pure fn is_null<T>(ptr: *const T) -> bool { ptr == null() }