Another round of portability fixes:

 * OpenBSD doesn't have idtype_t or the P_* constants either
 * FreeBSD has different values for the P_* constants
 * Android gives idtype_t a different signedness
 * Disable waitid on NetBSD as it causes a link failure - I think this
   may be a problem with the test environment

Author: zackw

src/unix/mod.rs

@@ -16,12 +16,19 @@ pub type cc_t = ::c_uchar;
 pub enum DIR {}
 pub enum locale_t {}
 
-// FIXME: This is technically wrong; idtype_t is specified as a C enum.
-// [ http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/sys_wait.h.html ]
+// idtype_t is specified as a C enum:
+// http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/sys_wait.h.html
 // However, FFI doesn't currently know how to ABI-match a C enum
-// (rust#28925, rust#34641) and *probably* the underlying type will be
-// c_uint everywhere since all of the enumerators are representable by c_uint.
-pub type idtype_t = ::c_uint;
+// (rust#28925, rust#34641).
+cfg_if! {
+    if #[cfg(target_os = "openbsd")] {
+        // idtype_t is not available
+    } else if #[cfg(target_os = "android")] {
+        pub type idtype_t = ::c_int;
+    } else {
+        pub type idtype_t = ::c_uint;
+    }
+}
 
 s! {
     pub struct group {
@@ -210,9 +217,21 @@ pub const PRIO_USER: ::c_int = 2;
 pub const PRIO_MIN: ::c_int = -20;
 pub const PRIO_MAX: ::c_int = 20;
 
-pub const P_ALL: idtype_t = 0;
-pub const P_PID: idtype_t = 1;
-pub const P_PGID: idtype_t = 2;
+cfg_if! {
+    if #[cfg(target_os = "openbsd")] {
+        // P_* constants are not available
+    } else if #[cfg(target_os = "freebsd")] {
+        // FreeBSD defines a great many more of these, and gives the
+        // standardized constants different values from everyone else.
+        pub const P_PID: idtype_t = 0;
+        pub const P_PGID: idtype_t = 2;
+        pub const P_ALL: idtype_t = 7;
+    } else {
+        pub const P_ALL: idtype_t = 0;
+        pub const P_PID: idtype_t = 1;
+        pub const P_PGID: idtype_t = 2;
+    }
+}
 
 cfg_if! {
     if #[cfg(dox)] {
@@ -458,7 +477,7 @@ extern {
                link_name = "waitpid$UNIX2003")]
     pub fn waitpid(pid: pid_t, status: *mut ::c_int, options: ::c_int)
                    -> pid_t;
-    #[cfg(not(target_os = "openbsd"))] // " if " -- appease style checker
+    #[cfg(not(any(target_os = "openbsd", target_os = "netbsd")))] // " if "
     #[cfg_attr(all(target_os = "macos", target_arch = "x86"),
                link_name = "waitid$UNIX2003")]
     pub fn waitid(idtype: idtype_t, id: id_t, infop: *mut ::siginfo_t,