x/mobile: Undefined symbols _res_9_nclose with Go 1.20

[xDragonZ]

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: #58159

[bcmills]

(attn @golang/ios)

[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?)

[xDragonZ]

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

[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.)

[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.

[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/ ..?)

[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.

[xDragonZ]

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

[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).

[tmm1]

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

[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

[dreacot]

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

[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.