crypto/rand: Read argument escapes to heap

[FiloSottile]

Currently, Read is implemented as io.ReadFull(Reader, b) which escape analysis can't track, so b escapes to the heap.

This is somewhat annoying, since it causes allocations in paths that could otherwise have none.

It should be possible to rewrite the package so that it doesn't escape on major platforms.

[mateusz834]

I' ve been investigating this once, and the remaining problem was that the rand.Reader is an interface and cases like:

var Reader io.Reader = &someStruct{}

will always cause the buffer passed to rand.Reader.Read to be escaped.

[mateusz834]

But i guess we can make the rand.Read function escape-free.

[gopherbot]

Change https://go.dev/cl/578516 mentions this issue: crypto/rand: make Read not escape the byte slice

[gopherbot]

Change https://go.dev/cl/602498 mentions this issue: crypto/rand: prevent Read argument from escaping to heap

[gopherbot]

Change https://go.dev/cl/616696 mentions this issue: runtime, internal/syscall/unix: mark getrandom vDSO as non-escaping

[gopherbot]

Change https://go.dev/cl/618275 mentions this issue: crypto/rand: skip TestAllocations if optimizations are off