* Regenerate code to update copyright end year to 2023
* Test behaviour of default values initialized in different ways
This adds repro tests for #126 and #129
* Fix Swap and CompareAndSwap for Value wrappers
Fixes#126, #129
All atomic types can be used without initialization, e.g., `var v
<AtomicType>`. This works fine for integer types as the initialized
value of 0 matches the default value for the user-facing type. However,
for Value wrappers, they are initialized to `nil`, which is a value that
can't be set (triggers a panic) so the default value for the user-facing
type is forced to be stored as a different value. This leads to multiple
possible values representing the default user-facing type.
E.g., an `atomic.String` with value `""` may be represented by the
underlying atomic as either `nil`, or `""`. This causes issues when we
don't handle the `nil` value correctly, causing to panics in `Swap` and
incorrectly not swapping values in `CompareAndSwap`.
This change fixes the above issues by:
* Requiring `pack` and `unpack` function in gen-atomicwrapper as the
only place we weren't supplying them was for `String`, and the
branching adds unnecessary complexity, especially with added `nil`
handling.
* Extending `CompareAndSwap` for `Value` wrappers to try an additional
`CompareAndSwap(nil, <new>)` only if the original `CompareAndSwap`
fails and the old value is the zero value.
This change is a renaming with no functional changes.
It includes the following renames:
* `val` for arguments that replace the atomic value (e.g., `Store`).
* `delta` for arguments that offset the atomic value (e.g., `Add`).
* `old`, `new` for arguments to `CAS`.
* `old` named return from `Swap`.
* `swapped` for named return from `CAS`.
This also matches the names used in the stdlib atomic interface:
https://golang.org/pkg/sync/atomic/
Float64 wraps a Uint64, and since Uint64 supports Swap, Float64 can also
support Swap. Enable the Swap method in the generated code, and add
tests.
This also adds a note for why String doesn't support Swap (though it
will be possible after Go 1.17+).
NaN != NaN when using Go's inbuilt operator, but the same is not true
when used with Float64.CAS. Add a note calling this out.
Changing this would be a behaviour change (requires a major version
bump), and is likely unsafe as it could lead to typical CAS loops
blocking forever.
To add the note, we copy the generated CAS method and extend the
documentation as the generator does not support per-method
customizations on the doc comments.
The generators gen-atomicint and gen-atomicwrapper hard-coded the year
into the licenses of the generated files.
Update to generate year ranges for the licenses, starting at 2020, going
to whatever today's year is.
The embedded `nocmp` field and other similar fields are unused in tests
and the rest of our code.
We can get the effect of `nocmp` without embedding the fields by using
`_ nocmp` as a field.
Generate atomic.Float64 with gen-valuewrapper by wrapping atomic.Uint64,
using math.Float64bits and math.Float64frombits to pack and unpack
float64 to uint64.
As in #73, separate each atomic type into its own file to ease review of
transition to generated code.
After moving every atomic to its own file, the atomic.go file serves
only as documentation, so rename it to doc.go.
