Correct broken unaligned load/store in armv5

[psolyca]

This PR fixes issue #1354.

armv5 devices and older (i.e. <= arm9 generation) require addresses that are stored to and loaded from to to be 4-byte aligned.

If this is not the case the lower 2 bits of the address are cleared and the load is performed in an unexpected order, including up to 3 bytes of data located prior to the address.

Inlined buckets are stored after their key in a page and since there is no guarantee that the key will be of a length that is a multiple of 4, it is possible for unaligned load/stores to occur when they are cast back to bucket and page pointer types.

The fix adds a new field to track whether the current architecture exhibits this issue, sets it on module load for ARM architectures, and then on bucket open, if this field is set and the address is unaligned, a byte-by-byte copy of the inlined bucket is performed.

The fixe commes from balena-os/bolt@97aba55
and has already been applied in the upstream boltdb repository boltdb/bolt#578

I already tested this fixe on my armv5 board with success.

Thanks

[lunny]

please use govendor and that will update vendor/vendor.json to follow the git rev.

[psolyca]

For now, I can not compile anymore. Do not know why, I have «out of memory» problem each time the build process is linking.

[psolyca]

Ok, I manage to compile commit ae9b02b in 3 ways :

• without any patch or update : same issue
• with manual patch : no more error
• with vendor update of BoltDB : no more error

I am updating my PR.

[ethantkoenig]

LGTM

[lunny]

LGTM