LibC+LookupServer: Compute magic number to avoid hardcoding

Author: https://github.com/BenWiederhake
Commit: https://github.com/SerenityOS/serenity/commit/34a8ee6da50
Pull-request: https://github.com/SerenityOS/serenity/pull/10748
Reviewed-by: https://github.com/alimpfard
Reviewed-by: https://github.com/trflynn89

Userland/Libraries/LibC/netdb.cpp

@@ -27,12 +27,13 @@ static in_addr_t* __gethostbyname_address_list_buffer[2];
 
 static hostent __gethostbyaddr_buffer;
 static in_addr_t* __gethostbyaddr_address_list_buffer[2];
-// XXX: IPCCompiler depends on LibC. Because of this, it cannot be compiled
+// IPCCompiler depends on LibC. Because of this, it cannot be compiled
 // before LibC is. However, the lookup magic can only be obtained from the
 // endpoint itself if IPCCompiler has compiled the IPC file, so this creates
 // a chicken-and-egg situation. Because of this, the LookupServer endpoint magic
 // is hardcoded here.
-static constexpr i32 lookup_server_endpoint_magic = 9001;
+// Keep the name synchronized with LookupServer/LookupServer.ipc.
+static constexpr i32 lookup_server_endpoint_magic = "LookupServer"sv.hash();
 
 // Get service entry buffers and file information for the getservent() family of functions.
 static FILE* services_file = nullptr;

Userland/Services/LookupServer/LookupServer.ipc

@@ -1,4 +1,5 @@
-endpoint LookupServer [magic=9001]
+// Keep the name synchronized with LibC/netdb.cpp, constant 'lookup_server_endpoint_magic'.
+endpoint LookupServer
 {
     lookup_name(String name) => (int code, Vector<String> addresses)
     lookup_address(String address) => (int code, String name)