fix undefined behavior due to incorrect packing on macosx

libc-test/build.rs

@@ -416,9 +416,6 @@ fn main() {
             // which is absent in glibc, has to be defined.
             "__timeval" if linux => true,
 
-            // The alignment of this is 4 on 64-bit OSX...
-            "kevent" | "shmid_ds" if apple && x86_64 => true,
-
             // This is actually a union, not a struct
             "sigval" => true,
 

src/unix/bsd/apple/mod.rs

@@ -245,7 +245,7 @@ s! {
         pub f_reserved: [::uint32_t; 8],
     }
 
-    // FIXME: this should have align 4 but it's got align 8 on 64-bit
+    #[repr(packed(4))]
     pub struct kevent {
         pub ident: ::uintptr_t,
         pub filter: ::int16_t,
@@ -524,7 +524,7 @@ s! {
         pub _key: ::key_t,
     }
 
-    // FIXME: this should have align 4 but it's got align 8 on 64-bit
+    #[repr(packed(4))]
     pub struct shmid_ds {
         pub shm_perm: ipc_perm,
         pub shm_segsz: ::size_t,