go: cmd/go: plugin versions do not match when built within vs. outside a module

A fix for this issue would require changes to the compiler (to prevent cross-package inlining when building plugins), and probably the linker (to interpret and record a signature for the package ABI). That’s possible, but it would be a lot of work to support a fairly esoteric build mode.

This is mostly a chicken and egg problem where many projects are not utilizing plugins due to their complicated build setup and other limitation (version incompatibility, requiring a main packet, linux only) while the plugin system does not get improved because very few projects are using it. However the demand certainly exists.

If look around, there are plenty of incomplete and partially-working attempt to deal with plugins, just because current system is way too restricting. At the end, a lot of efforts lost for nothing and 1) adoption of current plugins system is subpar, and 2) people waste time re-introducing wheel. I think, for most of it, if we introduce some kind of “unsafe” switch which disables next lines in src/runtime/plugin.go

	for _, pkghash := range md.pkghashes {
		if pkghash.linktimehash != *pkghash.runtimehash {
			md.bad = true
			return "", nil, "plugin was built with a different version of package " + pkghash.modulename
		}
	}

giving user options to make unsafe (and unrecommended) choice and deal with potential fallout on it’s own, adoptions of plugin system will jump tremendously, which on it’s own will lead to improvement of it. Solving chicken and egg issue from above.

Of course, it is not even close to be real solution. But rather temporary patch. But it give chance to actually use it.

In a current form it is not plugin system, it is merely lazy loading. The only realistic option to ensure than plugin will load, is to build is a part of source tree of the main code as part of the same compilation process.

or just rename to “lazy_load” to stop confusing people 😃

I’m on go 1.16 and still seeing this problem.

My personal opinion is that plugins need to be rethought completely. The current approach absolutely requires using the exact same version of Go to build the plugin and the application. That restriction makes plugins significantly less useful. Basically plugins were implemented as “this is something we can do with existing technology” rather than “this is something that people really need.”

So I think we need to go back to the beginning and decide what plugins are for, and then think about how to implement them. And we have to understand why plugins are better than simply executing a separate program and passing data back and forth on standard input and output.

To be clear, this issue is not the place for any of those discussions.

It is interesting to see this issue come up so many times over the past few years (or longer) and yet… little to no movement by the go team to fix this properly once and for all. The use of plugins if properly implemented allows any application that supports it the ability to be extended dynamically outside the context of the original creators of the application. Applications like IDEs, DAWs, and more make great use of extensibility in this way and provides a path of enhancement the original developers may not thought of or had the manpower/etc to do themselves. Similar to an open source project where many contribute.

I’ve seen in Rust a similar issue, where by code built as a dynamic loadable module using Rust’s ABI is “unstable” and only able to be loaded with specific versions that the app and module are compiled in. Sound familiar? Rust (and Zig) seem to have the ability to also load stable C ABI module, and compile to them however, though I won’t pretend to be an expert in how all that works and if it’s as good and easy to use.

As far as I can tell, this is the one built in area of Go that was never complete as there is no Windows implementation (not sure if ARM is supported?). So it’s like a half baked piece of work that the Go team gave up on and I am surprised it was never deprecated given its lack of support on Windows and last I read (some time ago) not fully working on Mac. Maybe that changed?

The Go team should figure out some sort of stable ABI option like Rust/zig have, but lets make it easier to use… following how easy Go typically is to use. Make it so we do something like go build -plugin … and we do NOT have to deal with any version issues. There should be no reason an app build in go 1.22 (or later since I will assume this “updated” idea I have here wouldn’t be possible to make it in 1.21 if even 1.22) can’t load a plugin built in go 1.23, 1.37, etc. As long as the tool/process builds it the same way, we developers shouldn’t have to do a bunch of fudgery crap to make it work across versions.

Until then, I don’t feel like there is much use in the built in plugin concept with the version mismatch issues. I am not sure if it works across minor versions… but how awful is it that you build an app in go 1.19 and a plugin compiled in go 1.19.1 or even 1.20 does not load/work in the app? It makes no sense really… unless the idea by the go team who started on this area figured it would only be used for in house use cases and thus no real need to make it work across versions. Granted, I wont pretend to know everything about why it doesn’t work, only that if it was truly impossible to do (which it isnt since rust/zig/c are able to do it), why put it in half baked and now see people trying to use it but running in to issues.

The current plugin mechanism does not allow you to avoid mixed package hashes. For example, this error occurs when a main application that references package A loads plugins that references A. I often use gophernotes to try to write notebook with Go. gophernotes reference mattn/go-runewidth. So gophernotes can not import mattn/go-runewidth on the notebooks. I have to disable Go code to avoid this.

diff --git a/src/runtime/plugin.go b/src/runtime/plugin.go
index cd7fc5f848..ace1b13ed9 100644
--- a/src/runtime/plugin.go
+++ b/src/runtime/plugin.go
@@ -48,12 +48,14 @@ func plugin_lastmoduleinit() (path string, syms map[string]interface{}, errstr s
                        throw("plugin: new module data overlaps with previous moduledata")
                }
        }
-       for _, pkghash := range md.pkghashes {
-               if pkghash.linktimehash != *pkghash.runtimehash {
-                       md.bad = true
-                       return "", nil, "plugin was built with a different version of package " + pkghash.modulename
+       /*
+               for _, pkghash := range md.pkghashes {
+                       if pkghash.linktimehash != *pkghash.runtimehash {
+                               md.bad = true
+                               return "", nil, "plugin was built with a different version of package " + pkghash.modulename
+                       }
                }
-       }
+       */

        // Initialize the freshly loaded module.
        modulesinit()

So its 2023 and i did run in the same issue as the rest here. I have a repostiory for my application and a respostiory for the plugin code. The idea was to write an application that can be fed by custom developed plugins for execution. Tho even considering the workarround with the alias it would be quite uncomfortable for people to use Plugins and this way of extending the apllication than.

I think this definatly should be considered to be solved since the net is allover filled with people hitting this issue and this thread now is ongoing for about 4 years with people asking for a solution.

There are several similar tickets; apologies if this is not the right place to comment.

If the path is different but the version of the libraries are identical, we get version mismatch errors. A way of replicating this is to build the calling program in a container, and build the plugin outside of the container. The paths may look like this:

# Calling
/go/pkg/mod/github.com/shirou/gopsutil@v2.18.11+incompatible/internal/common/common.go
# Called
/home/ser/go/pkg/mod/github.com/shirou/gopsutil@v2.18.11+incompatible/internal/common/common.go

Building locally, and where:

• the plugin is built using a go.mod with a specific date+revision version for the calling main program, and
• the calling application is built from a checkout at that version, verified that the version in the plugin go.mod matches the checked-out version with:

echo $(TZ=UTC git show -s --format=%cd --date=format-local:%Y%m%d%H%M%S HEAD | cut -b -19 |  tr -cd '[:digit:]')-$(git rev-parse HEAD | cut -b -12)

• and both programs being compiled with the same go executable, and
• using --trimpath on both, and
• both go.mod list the same go version dependency I get the same version incompatibility error with a different package:

# Error:
2:31:33 main.go:485: plugin.Open("dummy"): plugin was built with a different version of package github.com/xxxserxxx/gotop/v3/devices
$ #######################################################
$ strings ./gotop | grep 'v3/devices$'
go.link.pkghashbytes.github.com/xxxserxxx/gotop/v3/devices
go.link.pkghash.github.com/xxxserxxx/gotop/v3/devices
%github.com/xxxserxxx/gotop/v3/devices
go.link.pkghashbytes.github.com/xxxserxxx/gotop/v3/devices
go.link.pkghash.github.com/xxxserxxx/gotop/v3/devices
$ #######################################################
$ strings dummy.so | grep 'v3/devices$'
go.link.pkghashbytes.github.com/xxxserxxx/gotop/v3/devices
go.link.pkghash.github.com/xxxserxxx/gotop/v3/devices
github.com/xxxserxxx/gotop-dummygithub.com/xxxserxxx/gotop-dummygithub.com/xxxserxxx/gotop/v3/devices
%github.com/xxxserxxx/gotop/v3/devices
go.link.pkghashbytes.github.com/xxxserxxx/gotop/v3/devices
go.link.pkghash.github.com/xxxserxxx/gotop/v3/devices

I’ve played with copying the go.sum into the plugin directory so that it’s identical to the other project, and have made sure that the entries in both go.mods are the same (except for the plugin’s dependency on the main program).

If I add the following to the plugin’s go.mod:

replace github.com/xxxserxxx/gotop/v3 => ../gotop

then it works.

Edit

Rewrote some of the text to be more readable, I hope.

Edit 2

I made an error: I need to remove the -trimpath argument in addition to adding the replace directive in the go.mod, or else I still get a version incompatibility error. -trimpath appears to make things worse.

This is the same underlying problem as #29814.

The workaround should be to build both the plugin and the main binary from outside of their respective repositories, or (as you note) to use a replace directive when building locally.

do you mean to say, that the ext folder should be its own module, separate from the main app? would that work?