update changes, readme

[jdroenner]

No description provided.

[michaelkirk]

We recently hit some surprising behavior with a bindgen update

georust/proj#53

Note sure if this affects you, or maybe you've already dealt with it, but bindgen recently changed how size_t gets translated to rust.

It used to map size_t to usize. In rust, the byte size of usize changes depending on your platform to match the pointer size. On all "first class" rust platforms the size of usize in rust is equal to sizeof size_t in C.

But there's nothing in the c standard that says size_t needs to equal pointer width. So in theory, technically, they could be different.

...so the (controversial) decision was made to output a concretely sized type (based on the size of size_t on the person running bindgen).

So, long story short, if you are packaging and relying on pre-builting bindings and want them to work on 32bit and 64bit machines, you need to enable the --size_t-is-usize option for bindgen when you're packing your pre-built bindings.

You can trace the thread back from: rust-lang/rust-bindgen#1688

[jdroenner]

oh wow i did not know. So if i add .size_t_is_usize(true) to bindgen in build.rs it should work?

[jdroenner]

a created a PR for this: #127

[michaelkirk]

if i add .size_t_is_usize(true) to bindgen in build.rs it should work?

Yes, my understanding is that this will maintain the behavior from 0.53 and before.

I notice you're updating from bindgen 0.54, so that ship may have already sailed, but it would have only affected your pre-built bindings if you'd regenerated the bindings when you last updated bindgen.

[jdroenner]

i think all the bindings are older then the last bindgen update :)