x/mobile: gomobile iOS compile error: pointer is missing a nullability type specifier

[halseth]

Re-opening this, since the previous report was closed without a fix: #31015

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

$ go version
go version go1.12.1 darwin/amd64

Does this issue reproduce with the latest release?

Yes

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

go env Output

$ go env
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/johan/Library/Caches/go-build"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/johan/golang"
GOPROXY=""
GORACE=""
GOROOT="/usr/local/Cellar/go/1.12.1/libexec"
GOTMPDIR=""
GOTOOLDIR="/usr/local/Cellar/go/1.12.1/libexec/pkg/tool/darwin_amd64"
GCCGO="gccgo"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/dev/null"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/kq/3436m_v11sg0l7zqtmv2r1gw0000gn/T/go-build512725961=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

Install latest Xcode (10.2) and command line tools.
Install gomobile:

$ GO111MODULE=auto go get -u -v golang.org/x/mobile/cmd/...
$ GO111MODULE=off gomobile init
$ GO111MODULE=off gomobile version
gomobile version +167ebed Wed Mar 27 16:31:28 2019 +0000 (android,ios); androidSDK=<user>/Library/Android/sdk/platforms/android-28

Bulding lnd with gomobile

GO111MODULE=off ${GOPATH}/bin/gomobile bind -target=ios -tags="ios" -v -o ./build/Lndmobile.framework github.com/lightningnetwork/lnd/mobile

(see https://github.com/halseth/lnd/tree/mobile-support/mobile)

What did you expect to see?

Successfully build the iOS framework.

What did you see instead?

github.com/lightningnetwork/lnd/mobile
gobind
# gobind
In file included from _cgo_export.c:4:
In file included from go_lndmobilemain.go:10:
In file included from /var/folders/kq/3436m_v11sg0l7zqtmv2r1gw0000gn/T/gomobile-work-958859495/src/gobind/seq.h:7:
In file included from /var/folders/kq/3436m_v11sg0l7zqtmv2r1gw0000gn/T/gomobile-work-958859495/src/gobind/seq_darwin.h:10:
/var/folders/kq/3436m_v11sg0l7zqtmv2r1gw0000gn/T/gomobile-work-958859495/src/gobind/Universe.objc.h:23:29: error: pointer is missing a nullability type specifier (_Nonnull, _Nullable, or _Null_unspecified) [-Werror,-Wnullability-completeness]
/var/folders/kq/3436m_v11sg0l7zqtmv2r1gw0000gn/T/gomobile-work-958859495/src/gobind/Universe.objc.h:23:29: note: insert '_Nullable' if the pointer may be null
/var/folders/kq/3436m_v11sg0l7zqtmv2r1gw0000gn/T/gomobile-work-958859495/src/gobind/Universe.objc.h:23:29: note: insert '_Nonnull' if the pointer should never be null
/var/folders/kq/3436m_v11sg0l7zqtmv2r1gw0000gn/T/gomobile-work-958859495/src/gobind/Universe.objc.h:25:4: error: pointer is missing a nullability type specifier (_Nonnull, _Nullable, or _Null_unspecified) [-Werror,-Wnullability-completeness]
/var/folders/kq/3436m_v11sg0l7zqtmv2r1gw0000gn/T/gomobile-work-958859495/src/gobind/Universe.objc.h:25:4: note: insert '_Nullable' if the pointer may be null
/var/folders/kq/3436m_v11sg0l7zqtmv2r1gw0000gn/T/gomobile-work-958859495/src/gobind/Universe.objc.h:25:4: note: insert '_Nonnull' if the pointer should never be null
/var/folders/kq/3436m_v11sg0l7zqtmv2r1gw0000gn/T/gomobile-work-958859495/src/gobind/Universe.objc.h:25:30: error: pointer is missing a nullability type specifier (_Nonnull, _Nullable, or _Null_unspecified) [-Werror,-Wnullability-completeness]
/var/folders/kq/3436m_v11sg0l7zqtmv2r1gw0000gn/T/gomobile-work-958859495/src/gobind/Universe.objc.h:25:30: note: insert '_Nullable' if the pointer may be null
/var/folders/kq/3436m_v11sg0l7zqtmv2r1gw0000gn/T/gomobile-work-958859495/src/gobind/Universe.objc.h:25:30: note: insert '_Nonnull' if the pointer should never be null
/Users/johan/golang/bin/gomobile: darwin-arm: go build -tags ios dev experimental ios -v -ldflags -X github.com/lightningnetwork/lnd/build.Commit=queue/v1.0.1-166-gc14a8dca0826718ef8cea820d1b1662dee5bec72 -buildmode=c-archive -o /var/folders/kq/3436m_v11sg0l7zqtmv2r1gw0000gn/T/gomobile-work-958859495/lndmobile-arm.a gobind failed: exit status 2

Note: possible workaround is mentioned in the closed issue: #31015 (comment)

[bcmills]

CC @hyangah

[champo]

Opened golang/mobile#29 to solve this issue

[halseth]

Confirming that this is fixed as of 3e0bab5405d63a8f5dd9d9764a24c8e5ac4997fa (master).