Symbol not found: ___res_9_state

Question

Nick_Ni OP

Created Jul ’25

Replies 2

Boosts 0

Participants 3

When running my app with Xcode16.4, it crashed with the error:

dyld[1045]: Symbol not found: ___res_9_state

Referenced from: <8B329554-5BEF-38D0-BFCD-1731FA6120CB> /private/var/containers/Bundle/Application/00C941BA-E397-4D0B-B280-E75583FF2890/***.app/***.debug.dylib

Expected in: <7D74C679-8F55-3A01-9AA2-C205A4A19D3E> /usr/lib/libresolv.9.dylib

The ___res_9_state related code in my app is:

let state = __res_9_state()
res_9_ninit(state)
var servers = [res_9_sockaddr_union](repeating: res_9_sockaddr_union(), count: Int(MAXNS))
let found = Int(res_9_getservers(state, &servers, Int32(MAXNS)))
res_9_nclose(state)
if found > 0 {
    return Array(servers[0..<found]).filter() { $0.sin.sin_len > 0 }
} else {
    return []
}

Previously, __res_9_state() could run normally in Xcode 16.1

How to fix this problem?

Boost

Answer 1

DTS Engineer OP

Apple

Jul ’25

If you compare the header files for resolv.h included with the SDKs for Xcode 16.1 and Xcode 16.4, you'll see there's quite a signifiant difference. This is also visible in the Apple open source repository. In particular, note how this YYYYMMDD formatted macro in resolv.h jumped from this in Xcode 16.1:

#define	__RES	19991006

to this in Xcode 16.4:

#define	__RES	20090302

You should take a look at your overall code to make sure that it is compatible with those changes you can see by diffing the header files.

— Ed Ford,  DTS Engineer

0

Answer 2

DTS Engineer OP

Apple

Jul ’25

As my colleague Ed mentioned, the <resolv.h> interface has a lot of ‘interesting’ backstory. My general advice is to avoid that API wherever possible. However, before we dig into alternatives I want to ask about this:

When running my app with Xcode16.4, it crashed with the error:

I built a tiny test function that calls __res_9_state and called it from both a macOS program and an iOS app and both worked just fine. So where are you running your code? Specifically, what platform and what version of that platform?

Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

0