core: Split sys::align_of into min_align_of, pref_align_of

src/libcore/sys.rs

@@ -3,7 +3,8 @@
 export type_desc;
 export get_type_desc;
 export size_of;
-export align_of;
+export min_align_of;
+export pref_align_of;
 export refcount;
 export log_str;
 
@@ -43,8 +44,21 @@ fn size_of<T>() -> uint unsafe {
     rusti::size_of::<T>()
 }
 
-#[doc = "Returns the alignment of a type"]
-fn align_of<T>() -> uint unsafe {
+#[doc = "
+Returns the ABI-required minimum alignment of a type
+
+This is the alignment used for struct fields. It may be smaller
+than the preferred alignment.
+"]
+fn min_align_of<T>() -> uint unsafe {
+    // FIXME: use rusti::min_align_of after snapshot
+    // rusti::align_of::<T>()
+    fail "FIXME: uncomment the above line to use min_align_of";
+}
+
+#[doc = "Returns the preferred alignment of a type"]
+fn pref_align_of<T>() -> uint unsafe {
+    // FIXME: use rusti::pref_align_of after snapshot
     rusti::align_of::<T>()
 }
 
@@ -85,24 +99,24 @@ mod tests {
 
     #[test]
     fn align_of_basic() {
-        assert align_of::<u8>() == 1u;
-        assert align_of::<u16>() == 2u;
-        assert align_of::<u32>() == 4u;
+        assert pref_align_of::<u8>() == 1u;
+        assert pref_align_of::<u16>() == 2u;
+        assert pref_align_of::<u32>() == 4u;
     }
 
     #[test]
     #[cfg(target_arch = "x86")]
     #[cfg(target_arch = "arm")]
     fn align_of_32() {
-        assert align_of::<uint>() == 4u;
-        assert align_of::<*uint>() == 4u;
+        assert pref_align_of::<uint>() == 4u;
+        assert pref_align_of::<*uint>() == 4u;
     }
 
     #[test]
     #[cfg(target_arch = "x86_64")]
     fn align_of_64() {
-        assert align_of::<uint>() == 8u;
-        assert align_of::<*uint>() == 8u;
+        assert pref_align_of::<uint>() == 8u;
+        assert pref_align_of::<*uint>() == 8u;
     }
 }
 

src/rustc/middle/trans/debuginfo.rs

@@ -451,7 +451,7 @@ fn create_boxed_type(cx: @crate_ctxt, outer: ty::t, _inner: ty::t,
                                           ast::ty_uint(ast::ty_u), span);
     let scx = create_structure(file_node, ty_to_str(cx.tcx, outer), 0);
     add_member(scx, "refcnt", 0, sys::size_of::<uint>() as int,
-               sys::align_of::<uint>() as int, refcount_type.node);
+               sys::min_align_of::<uint>() as int, refcount_type.node);
     add_member(scx, "boxed", 0, 8, //XXX member_size_and_align(??)
                8, //XXX just a guess
                boxed.node);
@@ -502,9 +502,9 @@ fn create_vec(cx: @crate_ctxt, vec_t: ty::t, elem_t: ty::t,
     let size_t_type = create_basic_type(cx, ty::mk_uint(cx.tcx),
                                         ast::ty_uint(ast::ty_u), vec_ty_span);
     add_member(scx, "fill", 0, sys::size_of::<libc::size_t>() as int,
-               sys::align_of::<libc::size_t>() as int, size_t_type.node);
+               sys::min_align_of::<libc::size_t>() as int, size_t_type.node);
     add_member(scx, "alloc", 0, sys::size_of::<libc::size_t>() as int,
-               sys::align_of::<libc::size_t>() as int, size_t_type.node);
+               sys::min_align_of::<libc::size_t>() as int, size_t_type.node);
     let subrange = llmdnode([lltag(SubrangeTag), lli64(0), lli64(0)]);
     let (arr_size, arr_align) = size_and_align_of(cx, elem_t);
     let data_ptr = create_composite_type(ArrayTypeTag, "", file_node.node, 0,
@@ -512,7 +512,7 @@ fn create_vec(cx: @crate_ctxt, vec_t: ty::t, elem_t: ty::t,
                                          option::some(elem_ty_md.node),
                                          option::some([subrange]));
     add_member(scx, "data", 0, 0, // clang says the size should be 0
-               sys::align_of::<u8>() as int, data_ptr);
+               sys::min_align_of::<u8>() as int, data_ptr);
     let llnode = finish_structure(scx);
     ret @{node: llnode, data: {hash: ty::type_id(vec_t)}};
 }

src/test/run-pass/rec-align-32-bit.rs

@@ -22,7 +22,7 @@ fn main() {
     // Send it through the shape code
     let y = #fmt["%?", x];
 
-    #debug("align inner = %?", sys::align_of::<inner>()); // 8
+    #debug("align inner = %?", sys::pref_align_of::<inner>()); // 8
     #debug("size outer = %?", sys::size_of::<outer>());   // 12
     #debug("y = %s", y);                                  // (22, (0))