pcommon.Map.MoveTo() clears destination map when source and destination are the same

[rockdaboot]

Component(s)

pdata

What happened?

Describe the bug
If m and dst are equal and not empty, m.MoveTo(dst) results in empty maps dst and m.

Code:

opentelemetry-collector/pdata/pcommon/map.go

Line 248 in d79ffd3

func (m Map) MoveTo(dest Map) {

Expectation
MoveTo() should be a no-op if m and dst or the underlying internal maps are equal (as in "using same memory region").

Collector version

main branch

Environment information

No response

OpenTelemetry Collector configuration

Log output

Additional context

No response

[github-actions]

Pinging code owners:

• pdata: @bogdandrutu @dmitryax

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[dmitryax]

If m and dst are equal and not empty, m.MoveTo(dst) results in empty maps dst and m.

I can reproduce this with the following snippet

package main

import (
	"fmt"

	"go.opentelemetry.io/collector/pdata/pcommon"
)

func main() {
        src := pcommon.NewMap()
        src.PutStr("hello", "world")

        dst := src

        fmt.Printf("BEFORE  MoveTo → src=%v dst=%v\n", src.AsRaw(), dst.AsRaw())

        src.MoveTo(dst)

        fmt.Printf("AFTER  MoveTo → src=%v dst=%v\n", src.AsRaw(), dst.AsRaw())
}

It returns:

BEFORE  MoveTo → src=map[hello:world] dst=map[hello:world]
AFTER  MoveTo → src=map[] dst=map[]

MoveTo() should be a no-op if m and dst or the underlying internal maps are equal (as in "using same memory region").

The issue sounds like an UB case, but we can see if this can be achieved without any performance penalty.

@rockdaboot do you want to submit a PR?

[bogdandrutu]

@dmitryax this affects all MoveTo funcs, sent a fix.