socket: fix build error and warnings on mingw

* ext/socket/extconf.rb: check for if_nametoindex() for
  i686-w64-mingw32, and check for declarations of if_indextoname() and
  if_nametoindex().
* ext/socket/ifaddr.c (ifaddr_ifindex): not-implement unless
  if_nametoindex() is available.
* ext/socket/rubysocket.h: declare if_indextoname() and
  if_nametoindex() if available but not declared.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@40738 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 14 insertions, 1 deletions

diff --git a/ext/socket/extconf.rb b/ext/socket/extconf.rb
index 88e7366e37..458871fbd9 100644
--- a/ext/socket/extconf.rb
+++ b/ext/socket/extconf.rb
@@ -421,7 +421,20 @@ EOF
 
   have_func("getpeerucred(0, (ucred_t **)NULL)", headers) # SunOS
 
-  have_func('if_indextoname(0, "")', headers)
+  have_func_decl = proc do |name, headers|
+    if !checking_for("declaration of #{name}()") {!%w[int void].all? {|ret| try_compile(<<EOF)}}
+#{cpp_include(headers)}
+#{ret} #{name}(void);
+EOF
+      $defs << "-DNEED_#{name.tr_cpp}_DECL"
+    end
+  end
+  if have_func('if_indextoname(0, "")', headers)
+    have_func_decl["if_indextoname"]
+  end
+  if have_func('if_nametoindex("")', headers)
+    have_func_decl["if_nametoindex"]
+  end
 
   have_func("hsterror", headers)
   have_func('getipnodebyname("", 0, 0, (int *)0)', headers) # RFC 2553