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Plugins can't use different C libraries by CGO with the same symbol names #42854

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dsxack opened this issue Nov 27, 2020 · 4 comments
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Plugins can't use different C libraries by CGO with the same symbol names #42854

dsxack opened this issue Nov 27, 2020 · 4 comments
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@dsxack
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dsxack commented Nov 27, 2020

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

$ go version
go version go1.15.5 linux/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
go version go1.15.5 linux/amd64
root@2ce5210666df:/go# go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/root/.cache/go-build"
GOENV="/root/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD=""
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 -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build189801058=/tmp/go-build -gno-record-gcc-switches"

What did you do?

hello1.c:

I have a hello1/lib/hello1.c library and built it into hello1/lib/libhello1.a

#include <stdio.h>

void hello() {
    printf("Hello from C hello1.c\n");
}

hello2.c:

I have a hello2/lib/hello2.c library with the same function name hello that in hello1.c and built it into hello2/lib/libhello2.a

#include <stdio.h>

void hello() {
    printf("Hello from C hello2.c\n");
}

hello1.go:

I have a hello1/hello1.go and built it into hello1/hello1.so with go build -buildmode=plugin

package main

/*
#cgo LDFLAGS: -L${SRCDIR}/lib -lhello1

void hello();
*/
import "C"
import "fmt"

func Hello() {
	fmt.Println("Hello from Go plugin hello1.go")
	fmt.Println("Call C hello1.c")
	C.hello()
}

hello2.go:

I have a hello2/hello2.go and built it into hello2/hello2.so with go build -buildmode=plugin

package main

/*
#cgo LDFLAGS: -L${SRCDIR}/lib -lhello2

void hello();
*/
import "C"
import "fmt"

func Hello() {
	fmt.Println("Hello from Go plugin hello2.go")
	fmt.Println("Call C hello2.c")
	C.hello()
}

main.go:

I have a main.go in the root project dir and built it into main with go build.

package main

import (
	"fmt"
	"plugin"
)

func main() {
	p1, err := plugin.Open("hello1/hello1.so")
	if err != nil {
		panic(err)
	}
	fmt.Println("Load Go plugin hello1.so")

	p2, err := plugin.Open("hello2/hello2.so")
	if err != nil {
		panic(err)
	}
	fmt.Println("Load Go plugin hello2.so")

	h1, err := p1.Lookup("Hello")
	if err != nil {
		panic(err)
	}

	h2, err := p2.Lookup("Hello")
	if err != nil {
		panic(err)
	}

	fmt.Println("Call Go plugin hello1.go")
	h1.(func())()
	fmt.Println("\nCall Go plugin hello2.go")
	h2.(func())()
}

What did you expect to see?

Load Go plugin hello1.so
Load Go plugin hello2.so

Call Go plugin hello1.go
Hello from Go plugin hello1.go
Call C hello1.c
Hello from C hello1.c

Call Go plugin hello2.go
Hello from Go plugin hello2.go
Call C hello2.c
Hello from C hello2.c

What did you see instead?

I see Hello from C hello1.c at the last line but I expected Hello from C hello2.c

Load Go plugin hello1.so
Load Go plugin hello2.so

Call Go plugin hello1.go
Hello from Go plugin hello1.go
Call C hello1.c
Hello from C hello1.c

Call Go plugin hello2.go
Hello from Go plugin hello2.go
Call C hello2.c
Hello from C hello1.c
@dsxack dsxack changed the title Plugins can't use different CGO libraries with the same symbol names Plugins can't use different C libraries by CGO with the same symbol names Nov 27, 2020
@AlexRouSg
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AlexRouSg commented Nov 27, 2020 •
edited

If you only load hello2.so does it print what you expect?
Have you tried using __attribute__ ((visibility ("hidden"))) on the C functions with the same name?

@dsxack
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dsxack commented Nov 27, 2020 •
edited

@AlexRouSg yes, if I load hello2.so only it prints what I expect:

Load Go plugin hello2.so

Call Go plugin hello2.go
Hello from Go plugin hello2.go
Call C hello2.c
Hello from C hello2.c

Also I can't impact to C libraries code because it is vendor libraries.

@AlexRouSg
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What happens when you use the -fvisibility=hidden gcc flag?

@dsxack
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dsxack commented Nov 27, 2020 •
edited

@AlexRouSg yes, it works! Thank you!

Add -fvisibility=hidden gcc flag when to C libraries compile resolves my issue.

Load Go plugin hello1.so
Load Go plugin hello2.so

Call Go plugin hello1.go
Hello from Go plugin hello1.go
Call C hello1.c
Hello from C hello1.c

Call Go plugin hello2.go
Hello from Go plugin hello2.go
Call С hello2.c
Hello from C hello2.c

@dsxack dsxack closed this as completed Nov 27, 2020
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@dsxack @AlexRouSg @gopherbot