core: Start on a stack walker

src/libcore/stackwalk.rs

@@ -0,0 +1,54 @@
+import libc::uintptr_t;
+
+class frame {
+    let fp: uintptr_t;
+
+    new(fp: uintptr_t) {
+        self.fp = fp;
+    }
+}
+
+fn walk_stack(visit: fn(frame) -> bool) {
+    frame_address { |frame_pointer|
+        let frame_address = unsafe {
+            unsafe::reinterpret_cast(frame_pointer)
+        };
+        visit(frame(frame_address));
+    }
+}
+
+#[test]
+fn test() {
+    for walk_stack { |frame|
+        #debug("frame: %x", frame.fp);
+        // breakpoint();
+    }
+}
+
+fn breakpoint() {
+    rustrt::rust_dbg_breakpoint()
+}
+
+fn frame_address(f: fn(*u8)) {
+    rusti::frame_address(f)
+}
+
+native mod rustrt {
+    fn rust_dbg_breakpoint();
+}
+
+// FIXME: Unconditionalize after snapshot
+#[cfg(stage1)]
+#[cfg(stage2)]
+#[cfg(stage3)]
+#[abi = "rust-intrinsic"]
+native mod rusti {
+    fn frame_address(f: fn(*u8));
+}
+
+#[cfg(stage0)]
+mod rusti {
+    fn frame_address(_f: fn(*u8)) {
+        fail;
+    }
+}