Add alignment feature and use #[repr(align(x))]

Author: faern

Cargo.toml

@@ -20,6 +20,7 @@ appveyor = { repository = "rust-lang/libc", project_name = "rust-lang-libs/libc"
 [features]
 default = ["use_std"]
 use_std = []
+align = []
 
 [workspace]
 members = ["libc-test"]

src/fuchsia/mod.rs

@@ -166,8 +166,10 @@ s! {
         pub s_addr: in_addr_t,
     }
 
+    #[cfg_attr(feature = "align", repr(align(4)))]
     pub struct in6_addr {
         pub s6_addr: [u8; 16],
+        #[cfg(not(feature = "align"))]
         __align: [u32; 0],
     }
 

src/redox/net.rs

@@ -9,8 +9,10 @@ s! {
         pub s_addr: in_addr_t,
     }
 
+    #[cfg_attr(feature = "align", repr(align(4)))]
     pub struct in6_addr {
         pub s6_addr: [u8; 16],
+        #[cfg(not(feature = "align"))]
         __align: [u32; 0],
     }
 

src/unix/mod.rs

@@ -104,8 +104,10 @@ s! {
         pub s_addr: in_addr_t,
     }
 
+    #[cfg_attr(feature = "align", repr(align(4)))]
     pub struct in6_addr {
         pub s6_addr: [u8; 16],
+        #[cfg(not(feature = "align"))]
         __align: [u32; 0],
     }