Impl get_size::GetSize (behind feature flag) (v1 branch)

[amandasaurus]

Shows memory usage of the struct

cf. issue #331

This includes unittests, and I have briefly used this in real programmes successfully.

[mbrubeck]

It looks like this test is failing when both the "get-size" and "union" features are enabled. You can reproduce this failure by running cargo test --features get-size,union.

The test will also fail on non-64-bit platforms. You can fix both issues by changing this line to something like

#[cfg(all(feature = "get-size", target_pointer_with = "64", not(feature = "union")))]

[amandasaurus]

👍 Fixed. & new branch (w. clean history) pushed. I've also added some tests for when the union feature is active.

[mbrubeck]

Thanks! Published as smallvec 1.13.0.

[amandasaurus]

Unfortunately, this has a bug.

a Cargo.toml with:

[dependencies]
get-size = { version = "0.1.4", features = ["derive"] }
smallvec = { version = "1.13.0", features = ["get-size"] }

will fail to compile with:

error: cyclic package dependency: package `attribute-derive v0.6.1` depends on itself. Cycle:
package `attribute-derive v0.6.1`
    ... which satisfies dependency `attribute-derive = "^0.6"` (locked to 0.6.1) of package `get-size-derive v0.1.3`
    ... which satisfies dependency `get-size-derive = "^0.1.3"` (locked to 0.1.3) of package `get-size v0.1.4`
    ... which satisfies dependency `get-size = "^0.1"` (locked to 0.1.4) of package `smallvec v1.13.0`
    ... which satisfies dependency `smallvec = "^1.5"` (locked to 1.13.0) of package `proc-macro-utils v0.8.0`
    ... which satisfies dependency `proc-macro-utils = "^0.8.0"` (locked to 0.8.0) of package `attribute-derive-macro v0.6.1`
    ... which satisfies dependency `attribute-derive-macro = "^0.6.1"` (locked to 0.6.1) of package `attribute-derive v0.6.1`

However these dependencies works:

[dependencies]
get-size = { version = "0.1.4", features = ["derive"] }
smallvec = { git = "https://github.com/servo/rust-smallvec.git", rev="v1.13.0", features = ["get-size"] }

😖😖 But the v1.13.0 tag should be the same as the released 1.13.0, right?

[mbrubeck]

Hmm, that's annoying. As a workaround you can do this:

[dependencies]
get-size = "0.1.4"
get-size-derive = "0.1"
smallvec = { version = "1.13.0", features = ["get-size"] }

and replace #[derive(GetSize)] in your code with:

#[derive(get_size_derive::GetSize)]

but things will still break if you have dependencies outside of your control that enable the "derive" feature of get-size.

Perhaps it would be better to remove these impls from the smallvec crate, and add them to the get-size crate, if the author is willing.

But the v1.13.0 tag should be the same as the released 1.13.0, right?

Using a git dependency breaks the cycle because Cargo considers it a different crate than the crates.io dependency, so it ends up building two different copies of the smallvec code.

[mbrubeck]

I have reverted this change and yanked version 1.13.0 for now, until we figure out the best solution. Sorry about this. :(