Use a macro instead of a constant.

When using a constant, the libc-test thinks this constant
exists as an C equivalent.

Author: mneumann

src/unix/bsd/mod.rs

@@ -11,9 +11,9 @@ pub type pthread_t = ::uintptr_t;
 pub type nfds_t = ::c_uint;
 
 #[cfg(not(target_os = "dragonfly"))]
-const UTSNAME_LEN: usize = 256;
+macro_rules! utsname_len { () => (256) }
 #[cfg(target_os = "dragonfly")]
-const UTSNAME_LEN: usize = 32;
+macro_rules! utsname_len { () => (32) }
 
 s! {
     pub struct sockaddr {
@@ -90,11 +90,11 @@ s! {
     }
 
     pub struct utsname {
-        pub sysname: [::c_char; UTSNAME_LEN],
-        pub nodename: [::c_char; UTSNAME_LEN],
-        pub release: [::c_char; UTSNAME_LEN],
-        pub version: [::c_char; UTSNAME_LEN],
-        pub machine: [::c_char; UTSNAME_LEN],
+        pub sysname: [::c_char; utsname_len!()],
+        pub nodename: [::c_char; utsname_len!()],
+        pub release: [::c_char; utsname_len!()],
+        pub version: [::c_char; utsname_len!()],
+        pub machine: [::c_char; utsname_len!()],
     }
 
     pub struct msghdr {