Eval does not release memory/ has a memory leak

[andig]

The following program sample.go triggers an unexpected result

package main

import (
	"fmt"
	"runtime"
	"runtime/debug"
	"time"

	"github.com/traefik/yaegi/interp"
)

func main() {
	vm := interp.New(interp.Options{})
	if _, err := vm.Eval(`var price float64`); err != nil {
		panic(err)
	}

	for {
		if _, err := vm.Eval(`price = 1.0`); err != nil {
			panic(err)
		}

		debug.FreeOSMemory()

		var stats runtime.MemStats
		runtime.ReadMemStats(&stats)
		fmt.Println(stats.Alloc)

		time.Sleep(10 * time.Millisecond)
	}
}

Expected result

// steady memory consumption

Got

// growing memory consumption

Yaegi Version

0.16.1

Additional Notes

Running an Eval() against a VM without allocating new variables leaks memory. If no allocation happens within the VM, the memory profile of the VM should remain stable.

This seems to make the Yaegi VM unsuitable for long-running purposes.

[andig]

It looks as if the memory consumption comes from growing interp.roots (https://github.com/traefik/yaegi/blob/master/interp/ast.go#L938). Is this something that could be eliminated?