Golang crypto/rand: Read should not escape the input buffer

Go version

go1.22

Output of go env in your module/workspace:

n/a

What did you do?

Ran this benchmark:

func Benchmark(b *testing.B) {
    b.ReportAllocs()
    for range b.N {
        sink = cryptoRandRead()
    }
}

//go:noinline
func cryptoRandRead() (out [8]byte) {
    rand.Read(out[:])
    return out
}

What did you see happen?

Benchmark-24         1877874           616.4 ns/op         8 B/op          1 allocs/op

What did you expect to see?

Benchmark-24         1877874           616.4 ns/op         0 B/op          0 allocs/op

The Read function is a static function. With some work to the underlying implementation (and avoid going through an io.Reader), we should be able to make it not escape the input.

Thus, you could do something like:

var arr [32]byte
rand.Read(arr[:])

and know that it doesn't allocate.

Comment From: thepudds

See also #66779 and https://go.dev/cl/578516.

Comment From: gabyhelp

Related Issues

• https://github.com/golang/go/issues/66779
• https://github.com/golang/go/issues/33256
• https://github.com/golang/go/issues/66801
• https://github.com/golang/go/issues/16593
• https://github.com/golang/go/issues/45217

_{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}

Comment From: rsc

Duplicate of #66779.