Regression: "unaligned 64-bit atomic operation" on 32-bit systems

[arrogantrabbit]

Please look at this thread:

https://forum.duplicacy.com/t/duplicacy-3-2-2-crashes-on-arm-32-bit/8024/7

To reproduce: build 32-bit arm version of the library and try to use.

Regression:

• v1.9.0: no issues
• v1.12.0: fails.

The proposed solution is to use atomic.AlignedInt64 instead of int64 in the MemoryBackend struct, or reorder len and buf, ideally -- do both, to reduce waste of space on padding.

Quoting analysis from the linked post:

I believe this is an issue in storj.io/uplink, which was upgraded from v1.9.0 to v1.12.0 for CLI 3.2.1: gilbertchen/duplicacy@7cc1b42

This is the line caused the crash:
https://github.com/storj/uplink/blob/c46ff1e3c01a1ef00000e5bf3ae48f4e887f8466/private/storage/streams/buffer/backend.go#L38C31-L38C31

This is the definition of MemoryBackend:

uplink/private/storage/streams/buffer/backend.go

Lines 27 to 31 in c46ff1e

	type MemoryBackend struct {
	buf []byte
	len int64
	closed bool
	}

If they can simply swap buf and len like this then the error will go away:

type MemoryBackend struct {
  len    int64
  buf    []byte
  closed bool
}

[storj-gerrit]

Change private/storage/streams/buffer: fix unaligned LoadInt64 mentions this issue.

[egonelbre]

@arrogantrabbit Thank you for the report and analysis. It seems we forgot to run staticcheck for 32bit arm, which catches such issues.

[egonelbre]

PS: I created v1.12.1 release that has this issue fixed.