What version of Go are you using (go version)?

$ go version
go version go1.20 darwin/arm64

Does this issue reproduce with the latest release?

Using MacOS with Go 1.20 error, no issue in 1.19.5

What operating system and processor architecture are you using (go env)?

go env Output
$ go env
GO111MODULE=""
GOARCH="arm64"
GOBIN=""
GOCACHE="/Users/name/Library/Caches/go-build"
GOENV="/Users/name/Library/Application Support/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="arm64"
GOHOSTOS="darwin"
GOINSECURE=""
GOMODCACHE="/Users/name/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="darwin"
GOPATH="/Users/name/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/darwin_arm64"
GOVCS=""
GOVERSION="go1.20"
GCCGO="gccgo"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/dev/null"
GOWORK=""
CGO_CFLAGS="-O2 -g"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-O2 -g"
CGO_FFLAGS="-O2 -g"
CGO_LDFLAGS="-O2 -g"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -arch arm64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/hr/1lxcf_8s41dfqq139phd6twm0000gn/T/go-build1419606280=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

After compiling using gomobile bind -v -ldflags='-s -w' -target=ios -o libtest.xcframework github.com/example/test in terminal and import the libtest.xcframework library to xcode, it will show error in xcode when trying to compile ios app

What did you expect to see?

What did you see instead?

Undefined symbols for architecture arm64: "_res_9_nclose", referenced from: _internal/syscall/unix.libresolv_res_9_nclose_trampoline.abi0 in Libtest(go.o) "_res_9_ninit", referenced from: _internal/syscall/unix.libresolv_res_9_ninit_trampoline.abi0 in Libtest(go.o) "_res_9_nsearch", referenced from: _internal/syscall/unix.libresolv_res_9_nsearch_trampoline.abi0 in Libtest(go.o) ld: symbol(s) not found for architecture arm64 clang: error: linker command failed with exit code 1 (use -v to see invocation)

Related: https://github.com/golang/go/issues/58159

Comment From: bcmills

(attn @golang/ios)

Comment From: bcmills

import the library to xcode

Import how? (Is there something you need to configure in xcode to set the linker flags for the final executable?)

Comment From: xDragonZ

Import xcframework to xcode project target. No, nothing to configure in xcode

Comment From: bcmills

@xDragonZ, try adding libresolv.9.tbd and/or libresolv.tbd in the Linked Frameworks and Libraries section. (See https://mozilla.github.io/firefox-browser-architecture/experiments/2017-09-06-rust-on-ios.html.)

Comment From: xDragonZ

Thank you 🫡 finally got it working.

Passing extldflags=-lresolv to gomobile doesn't works but adding libresolv.tbd able to compile the ios app without error now.

Comment From: bcmills

Great! Want to send a CL to update the documentation? (Probably goes in one of the files in https://cs.opensource.google/go/x/mobile/+/master:cmd/gomobile/ ..?)

Comment From: gurupras

Could you please share how you got this working? Running into the same issue and somehow adding libresolv.tbd and libresolv.9.tbd (for me it shows under Apple SDK and not IOS SDK; not sure if that matters) does nothing.

Comment From: xDragonZ

@gurupras you need to add it to "Frameworks & Libraries" section too

Comment From: drew-512

Hi friends,

Not clear if downstream now has to deal with this from now on, or if this will be addressed upstream (making many gophers happy).

Comment From: tmm1

Adding to Frameworks & Libraries wasn't working for me. I had to go to Build Phases > Link Libraries and add it there

Comment From: yulianaboglione

Hola puedes dejar lo Pasos que hiciste plis??? Tengo el mismo problema y no entiendo bien lo qué hay que hacer por favor necesito saber qué fue lo que hizo

Comment From: dreacot

include -tags=netgo while compiling e.g gomobile bind -v -tags=netgo -ldflags='-s -w' -target=ios -o libtest.xcframework

Comment From: notatestuser

Unfortunately, the suggested fix to use -tags=netgo appears to cause DNS resolution issues on real iOS devices running iOS 17+. It seems that Apple is preventing DNS resolvers embedded by apps to work properly.

Comment From: newswangerd

Unfortunately, the suggested fix to use -tags=netgo appears to cause DNS resolution issues on real iOS devices running iOS 17+. It seems that Apple is preventing DNS resolvers embedded by apps to work properly.

If anyone else is running into the DNS resolution issue, I found a fix for it here: https://github.com/ipfs-shipyard/gomobile-ipfs/issues/19

I copied the fix linked to that ticket by adding this to the entrypoint for my library to set the system wide resolver. 

    var dialer net.Dialer
    net.DefaultResolver = &net.Resolver{
        PreferGo: false,
        Dial: func(context context.Context, _, _ string) (net.Conn, error) {
            conn, err := dialer.DialContext(context, "udp", "84.200.69.80:53")
            if err != nil {
                return nil, err
            }
            return conn, nil
        },
    }

This worked but I don't know why or how. It looks like it's hard coding a specific DNS server, which I'm not a fan of. I'm going to do some more experimenting to see if I can find a better workaround, but I'll leave this here in case anyone else runs into the same problem.

Comment From: newswangerd

I finally figured out why it wasn't working for me to link libresolve like others were saying. I'm using flutter and I had to go link it from my pods, rather than the main app. That allowed me to remove the net.Dialer solution

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