Merge #721

721: Enable setresuid/setresgid on FreeBSD and OpenBSD r=asomers

Fixes #717 

This PR enables `setresuid` and `setresgid` on FreeBSD and OpenBSD. These functions are not present on NetBSD, macOS, and iOS as far as I can tell.

CHANGELOG.md

@@ -19,6 +19,8 @@ This project adheres to [Semantic Versioning](http://semver.org/).
   has changed type from `c_int` to `SockProtocol`.
   It accepts a `None` value for default protocol that was specified with zero using `c_int`.
   ([#647](https://github.com/nix-rust/nix/pull/647))
+- Exposed `unistd::setresuid` and `unistd::setresgid` on FreeBSD and OpenBSD
+  ([#721](https://github.com/nix-rust/nix/pull/721))
 
 ## [0.9.0] 2017-07-23
 

src/unistd.rs

@@ -15,9 +15,13 @@ use void::Void;
 use sys::stat::Mode;
 use std::fmt;
 
-#[cfg(any(target_os = "linux", target_os = "android"))]
+#[cfg(any(target_os = "android", target_os = "linux"))]
 pub use self::linux::*;
 
+#[cfg(any(target_os = "android", target_os = "freebsd",
+          target_os = "linux", target_os = "openbsd"))]
+pub use self::setres::*;
+
 /// User identifier
 ///
 /// Newtype pattern around `uid_t` (which is just alias). It prevents bugs caused by accidentally
@@ -1601,12 +1605,10 @@ pub fn sysconf(var: SysconfVar) -> Result<Option<c_long>> {
     }
 }
 
-#[cfg(any(target_os = "linux", target_os = "android"))]
+#[cfg(any(target_os = "android", target_os = "linux"))]
 mod linux {
-    use libc;
     use sys::syscall::{syscall, SYSPIVOTROOT};
     use {Errno, Result, NixPath};
-    use super::{Uid, Gid};
 
     pub fn pivot_root<P1: ?Sized + NixPath, P2: ?Sized + NixPath>(
             new_root: &P1, put_old: &P2) -> Result<()> {
@@ -1620,6 +1622,14 @@ mod linux {
 
         Errno::result(res).map(drop)
     }
+}
+
+#[cfg(any(target_os = "android", target_os = "freebsd",
+          target_os = "linux", target_os = "openbsd"))]
+mod setres {
+    use libc;
+    use {Errno, Result};
+    use super::{Uid, Gid};
 
     /// Sets the real, effective, and saved uid.
     /// ([see setresuid(2)](http://man7.org/linux/man-pages/man2/setresuid.2.html))