cmd/go: missing or invalid package binary for binary-only package with buildmode=plugin

[twyvip]

Please answer these questions before submitting your issue. Thanks!

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

go version go1.9.2 linux/amd64

Does this issue reproduce with the latest release?

yes

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

GOARCH="amd64"
GOBIN="/test/go/bin"
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/test/adcloud_code/adroot/golang:/test/adcloud_code/tangwenyi/:/test/adframework/golang/trunk:/test/adkfw_application/trunk"
GORACE=""
GOROOT="/test/go"
GOTOOLDIR="/test/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
CC="gcc"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build207457534=/tmp/go-build"
CXX="g++"
CGO_ENABLED="1"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"

What did you do?

1. I have one file in /root/work/go/src/say named say.go
   package say

import "fmt"
func Say(s string) string {
	return fmt.Sprintf("hello %s", s)
}

2. I try to build it to .a file go build -i -o $GOPATH/pkg/linux_amd64/say.a

3. change /root/work/go/src/say/say.go to

//go:binary-only-package

package say

4. another file /root/work/go/src/say/work/v1.go

package v1
import (
	"fmt"
	"say"
)
func SayToBob() {
	fmt.Println(say.Say("Bob"))
}

5. the main file /root/work/go/src/say/work/main.go

package main
import (
	"say/work/v1"
)
func main() {
	v1.SayToBob()
}

6. run main.go go run /root/work/go/src/say/work/main.go

go run main.go
hello Bob
that's right

7. but in fact, i need to build SayToBob as plugin to hot reload,run
   go build -buildmode=plugin -o /root/work/go/src/say/work/v1/plugin.so /root/work/go/src/say/work/v1/v1.go
   missing or invalid package binary for binary-only package say

If possible, provide a recipe for reproducing the error.
A complete runnable program is good.
A link on play.golang.org is best.

What did you expect to see?

can build plugin

What did you see instead?

can't build plugin
missing or invalid package binary for binary-only package say

[odeke-em]

Thank you for filing this issue @twyvip and welcome to Go!

Kindly paging @ianlancetaylor @rsc

[bcmills]

Binary-only packages are a completely separate mechanism from -buildmode=plugin.

It's not obvious to me what's going in here, but given that binary-only packages are on the way out (#28152), I would suggest using plugins instead (https://golang.org/pkg/plugin/).

I also note that most of the commands you list involve explicit .go source files. I would generally expect to see package paths instead; the use of explicit files instead of packages may be related to the other symptoms you encountered.

[twyvip]

@bcmills Hello, I saw that you closed my question, but I still can't find out how to solve my problem from your answer. Is golang not using Binary-only packages (.a file) in plugin? ? Or is there a problem with my use? How can I solve my problem?
My application scenario is that I have to compile a plugin, but I referenced the .a library in the plugin. At this point I am going to compile plugin go build -buildmode=plugin -o /root/work/go/src/say/work/ V1/plugin.so will report the following error: missing or invalid package binary for binary-only package say
Thank you. I don't know where the problem is? I hope you can give pointers?

[bcmills]

My application scenario is that I have to compile a plugin, but I referenced the .a library in the plugin.

Sounds like your plugin will need to be changed to load a plugin of its own, then. (Better still, can you build the plugin's dependencies from source?)

[twyvip]

@bcmills I use the .a library in the plugin code. When I have the source code of the .a library, I can compile the plugin successfully. However, when I only have the .a library and have no source code, the compiler will give me an error, missing or invalid package binary for binary-only package say。My detailed steps are described above，Can you tell me what's wrong？thanks！

[bcmills]

If you do have the source code, you should build the plugin against the source code.

If you do not have the source code, you will need to convert the package that was previously binary-only to be a plugin instead.

[dzpt]

@bcmills plugin is quite different thing from binary-only package.
If you have ever used C++ or Swift it works like binary-only package. Using plugin in Go is painful, code will be 100 times longer while methods aren't exposed to be used. It's suitable for CLI app rather than large scale framework.