res_init has many names

macOS uses res_9_init: https://github.com/practicalswift/osx/blob/3908694d6328baa293f0d7fc337348c01d13ed8f/src/libresolv/resolv.h#L316
Solaris uses res_init: https://java.net/projects/solaris/sources/on-src/content/usr/src/head/resolv.h
OpenBSD uses __res_init: https://github.com/openbsd/src/blob/f3b3b7c7ca9a921db3a5650eed40f2b2e4d731d8/include/resolv.h#L268
FreeBSD uses __res_init: https://github.com/freebsd/freebsd/blob/6911f4a88c9832e5985b788f5e84010424f9e020/include/resolv.h#L290
NetBSD uses __res_init: http://ftp.netbsd.org/pub/NetBSD/NetBSD-current/src/include/resolv.h
glibc uses __res_init: https://github.com/lattera/glibc/blob/a2f34833b1042d5d8eeb263b4cf4caaea138c4ad/resolv/resolv.h#L259
eglibc uses __res_init: https://github.com/Xilinx/eglibc/blob/7f0bcce417c47aefad06ddfec7cd4ced3a4e10ff/resolv/resolv.h#L259
musl uses res_init: https://github.com/runtimejs/musl-libc/blob/0a11d7cb13e243782da36e2e5747b8b151933cca/include/resolv.h#L128

Author: jonhoo

src/unix/mod.rs

@@ -694,7 +694,13 @@ extern {
                        res: *mut *mut addrinfo) -> ::c_int;
     pub fn freeaddrinfo(res: *mut addrinfo);
     pub fn gai_strerror(errcode: ::c_int) -> *const ::c_char;
-    #[link_name = "__res_init"]
+    #[cfg_attr(all(unix,
+                   not(target_os = "macos"),
+                   not(target_os = "solaris"),
+                   not(target_env = "musl")
+                   ),
+               link_name = "__res_init")]
+    #[cfg_attr(target_os = "macos", link_name = "res_9_init")]
     pub fn res_init() -> ::c_int;
 
     #[cfg_attr(target_os = "netbsd", link_name = "__gmtime_r50")]