cmd/cgo: building fully statically linked executable for Android fails when cgo is enabled

[leleliu008]

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

go version go1.20.3 linux/amd64

Does this issue reproduce with the latest release?

Yes

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

GO111MODULE="auto"
GOARCH="arm64"
GOBIN=""
GOCACHE="/home/leleliu008/.cache/go-build"
GOENV="/home/leleliu008/.config/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/home/leleliu008/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="android"
GOPATH="/home/leleliu008/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/home/linuxbrew/.linuxbrew/Cellar/go/1.20.3/libexec"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/home/linuxbrew/.linuxbrew/Cellar/go/1.20.3/libexec/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="go1.20.3"
GCCGO="gccgo"
AR="/home/leleliu008/.ndk-pkg/android-ndk-r23b/toolchains/llvm/prebuilt/linux-x86_64/bin/llvm-ar"
CC="/home/leleliu008/.ndk-pkg/core/bin/proxy-target-cc"
CXX="/home/leleliu008/.ndk-pkg/core/bin/proxy-target-c++"
CGO_ENABLED="1"
GOMOD="/home/leleliu008/.ndk-pkg/installing/android-31/arm64-v8a/yq/src/go.mod"
GOWORK=""
CGO_CFLAGS="--sysroot /home/leleliu008/.ndk-pkg/android-ndk-r23b/toolchains/llvm/prebuilt/linux-x86_64/sysroot -Qunused-arguments -fPIC -fno-common -Os"
CGO_CPPFLAGS="-I/home/leleliu008/.ndk-pkg/installing/android-31/arm64-v8a/yq/include --sysroot /home/leleliu008/.ndk-pkg/android-ndk-r23b/toolchains/llvm/prebuilt/linux-x86_64/sysroot -Qunused-arguments -include /home/leleliu008/.ndk-pkg/installing/android-31/arm64-v8a/yq/include/ndk-pkg-common.h -DNDEBUG"
CGO_CXXFLAGS="--sysroot /home/leleliu008/.ndk-pkg/android-ndk-r23b/toolchains/llvm/prebuilt/linux-x86_64/sysroot -Qunused-arguments -fPIC -fno-common -Os"
CGO_FFLAGS="-O2 -g"
CGO_LDFLAGS="-L/home/leleliu008/.ndk-pkg/installing/android-31/arm64-v8a/yq/lib --sysroot /home/leleliu008/.ndk-pkg/android-ndk-r23b/toolchains/llvm/prebuilt/linux-x86_64/sysroot -Wl,--as-needed -Wl,-z,muldefs -Wl,--allow-multiple-definition -static --static -ffunction-sections -fdata-sections -Wl,--gc-sections -Wl,--no-dynamic-linker -Wl,-S"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -pthread -fno-caret-diagnostics -Qunused-arguments -Wl,--no-gc-sections -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build155171888=/tmp/go-build -gno-record-gcc-switches"

What did you do?

go build -trimpath -v -ldflags ' -s -w -linkmode external "-extldflags=-static"' -tags release

What did you expect to see?

successfully built

What did you see instead?

/home/linuxbrew/.linuxbrew/Cellar/go/1.20.3/libexec/pkg/tool/linux_amd64/link: running /home/leleliu008/.ndk-pkg/core/bin/proxy-target-cc failed: exit status 1
ld: error: undefined symbol: __android_log_vprint
>>> referenced by gcc_android.c
>>>               /tmp/go-link-1481358754/000008.o:(fatalf)

ld: error: undefined symbol: dlopen
>>> referenced by gcc_android.c
>>>               /tmp/go-link-1481358754/000008.o:(inittls)

ld: error: undefined symbol: dlsym
>>> referenced by gcc_android.c
>>>               /tmp/go-link-1481358754/000008.o:(inittls)

ld: error: undefined symbol: dlclose
>>> referenced by gcc_android.c
>>>               /tmp/go-link-1481358754/000008.o:(inittls)
clang-12: error: linker command failed with exit code 1 (use -v to see invocation)

more

https://github.com/golang/go/blob/master/src/runtime/cgo/gcc_android.c

gcc_android.c rely on liblog.so and libdl.so

Note: Android NDK do not provides liblog.a

statically linked executable can not use functions in libdl.

to get runtime os SDK API Level, I usually use follwoing code:

char buff[PROP_VALUE_MAX];

int n = __system_property_get("ro.build.version.sdk", buff);

if (n > 0) {
    return 0;
} else {
    return -1; 
}

[bcmills]

(CC @golang/android)

[mknyszek]

In triage, we're not sure if building a fully static Android executable is supported. Assigned to the only person in @golang/android for more thoughts and details.