use offset_of! macro from field_offset

Cargo.toml

@@ -21,6 +21,7 @@ ast = {path = "src/ast"}
 utils = {path = "src/utils"}
 gc = {path = "src/gc"}
 
+field-offset = "0.1.1"
 libloading = "0.3"
 lazy_static = "0.1.15"
 log = "0.3.5"

src/gc/Cargo.toml

@@ -23,4 +23,5 @@ log = "0.3.5"
 simple_logger = "0.4.0"
 aligned_alloc = "0.1.2"
 crossbeam = "0.2.8"
-rustc-serialize = "*"
\ No newline at end of file
+rustc-serialize = "*"
+field-offset = "0.1.1"
\ No newline at end of file

src/gc/src/heap/immix/immix_mutator.rs

@@ -26,7 +26,6 @@ lazy_static! {
 const TRACE_ALLOC_FASTPATH : bool = true;
 
 #[repr(C)]
-// do not change the layout (unless change the offset of fields correspondingly)
 pub struct ImmixMutatorLocal {
     id        : usize,
     
@@ -53,12 +52,8 @@ pub struct ImmixMutatorLocal {
 }
 
 lazy_static! {
-    pub static ref CURSOR_OFFSET : usize = mem::size_of::<usize>()
-                + mem::size_of::<*mut u8>() * 2
-                + mem::size_of::<Address>();
-                
-    pub static ref LIMIT_OFFSET : usize = *CURSOR_OFFSET
-                + mem::size_of::<Address>();
+    pub static ref CURSOR_OFFSET : usize = offset_of!(ImmixMutatorLocal=>cursor).get_byte_offset();
+    pub static ref LIMIT_OFFSET  : usize = offset_of!(ImmixMutatorLocal=>limit).get_byte_offset();
 }
 
 pub struct ImmixMutatorGlobal {

src/gc/src/lib.rs

@@ -7,6 +7,8 @@ extern crate simple_logger;
 extern crate aligned_alloc;
 extern crate crossbeam;
 extern crate rustc_serialize;
+#[macro_use]
+extern crate field_offset;
 
 use std::sync::atomic::Ordering;
 

src/lib.rs

@@ -6,6 +6,8 @@ extern crate rustc_serialize;
 extern crate stderrlog;
 #[macro_use]
 extern crate maplit;
+#[macro_use]
+extern crate field_offset;
 
 #[macro_use]
 pub extern crate ast;

src/runtime/thread.rs

@@ -197,8 +197,6 @@ pub enum MuStackState {
 }
 
 #[repr(C)]
-#[allow(improper_ctypes)]
-// do not change the layout (unless change the offset of fields correspondingly)
 pub struct MuThread {
     pub hdr: MuEntityHeader,
     pub allocator: mm::Mutator,
@@ -213,15 +211,10 @@ pub struct MuThread {
 
 // this depends on the layout of MuThread
 lazy_static! {
-    pub static ref ALLOCATOR_OFFSET : usize = mem::size_of::<MuEntityHeader>();
-
-    pub static ref NATIVE_SP_LOC_OFFSET : usize = *ALLOCATOR_OFFSET
-                + mem::size_of::<mm::Mutator>()
-                + mem::size_of::<Option<Box<MuStack>>>();
-
-    pub static ref USER_TLS_OFFSET : usize = *NATIVE_SP_LOC_OFFSET + mem::size_of::<Address>();
-
-    pub static ref EXCEPTION_OBJ_OFFSET : usize = *USER_TLS_OFFSET + mem::size_of::<Address>();
+    pub static ref ALLOCATOR_OFFSET     : usize = offset_of!(MuThread=>allocator).get_byte_offset();
+    pub static ref NATIVE_SP_LOC_OFFSET : usize = offset_of!(MuThread=>native_sp_loc).get_byte_offset();
+    pub static ref USER_TLS_OFFSET      : usize = offset_of!(MuThread=>user_tls).get_byte_offset();
+    pub static ref EXCEPTION_OBJ_OFFSET : usize = offset_of!(MuThread=>exception_obj).get_byte_offset();
 }
 
 impl fmt::Display for MuThread {