You can create Go plugins too.
> On Oct 8, 2019, at 7:57 AM, Vitaly Isaev <vitalyisa...@gmail.com> wrote:
>
>
> Suggest we're implementing a very specific Go application like data migrator
> (for example, the one that transfers data from old database to new database
> with different data types). Therefore, this application must be compiled with
> two different versions of one library (e.g. v1 and v2). It seems to be
> impossible in terms of Go modules (see this ticket), but can we do this trick
> with C shared libraries?
>
> Minimal example:
>
> v1/lib.h
> #ifndef LIBCGO_MULTIVERSION_V1
> #define LIBCGO_MULTIVERSION_V1
>
> int add(int a, int b);
>
> #endif
>
> v1/lib.c
> #include "lib.h"
>
> int add(int a, int b) {
> return a + b;
> }
>
> v1/lib.go
> package cgomultiversion
>
> // #cgo LDFLAGS: -l:libcgomultiversion.so.1
> // #include <cgomultiversion_v1/lib.h>
> import "C"
>
> func Add(a, b int) int {
> return int(C.add(C.int(a), C.int(b)))
> }
>
> v2/lib.h
> #ifndef LIBCGO_MULTIVERSION_V2
> #define LIBCGO_MULTIVERSION_V2
>
> int add(int a, int b);
>
> #endif
>
> v2/lib.c
> #include "lib.h"
>
> int add(int a, int b) {
> // for tests purposes addition is replaced with multiplication in v2
> return a * b;
> }
>
> v2/lib.go
> package cgomultiversion
>
> // #cgo LDFLAGS: -l:libcgomultiversion.so.2
> // #include <cgomultiversion_v2/lib.h>
> import "C"
>
> func Add(a, b int) int {
> return int(C.add(C.int(a), C.int(b)))
> }
>
> Finally we have a test that tries to utilize both versions of C library:
> package cgomultiversion
>
> import (
> "testing"
> "github.com/stretchr/testify/assert"
> cgomultiversion1 "github.com/vitalyisaev2/cgo_multiversion_go_lib/v1"
> cgomultiversion2 "github.com/vitalyisaev2/cgo_multiversion_go_lib/v2"
> )
>
> func TestAdd(t *testing.T) {
> assert.Equal(t, 10, cgomultiversion1.Add(5, 5))
> assert.Equal(t, 25, cgomultiversion2.Add(5, 5))
> }
>
> This won't compile because of naming conflict on the C side:
> go test -count=1 -v
> # github.com/vitalyisaev2/cgo_multiversion_go_lib.test
> /usr/local/go/pkg/tool/linux_amd64/link: running gcc failed: exit status 1
> /usr/bin/ld: /tmp/go-link-218143790/000005.o: in function `add':
> /home/isaev/go/src/github.com/vitalyisaev2/cgo_multiversion_go_lib/v2/lib.c:6:
> multiple definition of `add';
> /tmp/go-link-218143790/000002.o:/home/isaev/go/src/github.com/vitalyisaev2/cgo_multiversion_go_lib/v1/lib.c:5:
> first defined here
> collect2: error: ld returned 1 exit status
>
>
> Full example is available at:
> https://github.com/vitalyisaev2/cgo_multiversion_go_lib
>
> Is it possible to achieve this with some other methods? Thanks a lot.
>
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