Fix TCPSocket segfault on missing host and 0 port (#4177)

will · bcardiff · commit 3c74890c0530 · 2017-03-27T10:53:32.000-03:00
Prior to this patch, `TCPSocket.new("whatever", 0)` would cause
    Invalid memory access (signal 11) at address 0x0
diff --git a/spec/std/socket_spec.cr b/spec/std/socket_spec.cr
@@ -542,6 +542,12 @@ describe TCPSocket do
       TCPSocket.new("localhostttttt", 12345)
     end
   end
+
+  it "fails (rather than segfault on darwin) when host doesn't exist and port is 0" do
+    expect_raises(Socket::Error, /No address found for localhostttttt:0/) do
+      TCPSocket.new("localhostttttt", 0)
+    end
+  end
 end
 
 describe UDPSocket do
diff --git a/src/socket/addrinfo.cr b/src/socket/addrinfo.cr
@@ -86,6 +86,15 @@ class Socket
         hints.ai_flags |= LibC::AI_NUMERICSERV
       end
 
+      # On OS X < 10.12, the libsystem implementation of getaddrinfo segfaults
+      # if AI_NUMERICSERV is set, and servname is NULL or 0.
+      {% if flag?(:darwin) %}
+        if (service == 0 || service == nil) && (hints.ai_flags & LibC::AI_NUMERICSERV)
+          hints.ai_flags |= LibC::AI_NUMERICSERV
+          service = "00"
+        end
+      {% end %}
+
       case ret = LibC.getaddrinfo(domain, service.to_s, pointerof(hints), out ptr)
       when 0
         # success
