10:08 <re_irc> <@thejpster:matrix.org> How do we feel about default features vs negative features?

10:09 <re_irc> <@thejpster:matrix.org> I have a crate for a chip, and there's some feature that is generally useful for people, but some people might want to do their own thing.

10:10 <re_irc> <@thejpster:matrix.org> (specifically, including a default memory.x file in the BSP, as the particular board you have defines the flash-chip size).

10:12 <re_irc> <@thejpster:matrix.org> I recall people don't like "negative features", as in:

10:12 <re_irc> <@thejpster:matrix.org> ```toml

10:12 <re_irc> ... long message truncated: https://psion.agg.io/_matrix/media/r0/download/psion.agg.io/a5d111e46629c3ef0d099b349b127b099e610b94aea7736937c94170c527f710 (7 lines)

10:12 <re_irc> <@thejpster:matrix.org> rp_hal = { version = "1.0", features=["no_memory_file"] }

10:12 <re_irc> <@thejpster:matrix.org> The alternative is:

10:13 <re_irc> <@thejpster:matrix.org> Oh, also the issue is that I can't have both the HAL and the BSP copy over a memory.x file, as I don't think the linker order is well defined. But the HAL needs one otherwise the examples don't build.

10:13 <re_irc> <@dirbaio:matrix.org> negative features are bad, because crate A might enable the negative feature, which breaks crate B which wants to use the feature

10:13 <re_irc> <@dirbaio:matrix.org> which can't happen with positive features, each crate enables what it needs

10:14 <re_irc> <@thejpster:matrix.org> The feature in this case is "don't copy memory.x out ${OUT_DIR} because another crate in the tree is going to do it"

10:14 <re_irc> <@dirbaio:matrix.org> for memory.x it *might* be fine because it doesn't really remove stuff from the Rust API

10:14 <re_irc> <@thejpster:matrix.org> I think my negative feature is actually a positive feature

10:14 <re_irc> <@dirbaio:matrix.org> `custom-memory-x`

10:14 <re_irc> <@dirbaio:matrix.org> haha

10:15 <re_irc> <@dirbaio:matrix.org> it's positive now!

10:15 <re_irc> <@thejpster:matrix.org> Nice

10:15 <re_irc> <@dirbaio:matrix.org> I'd just make it `memory-x` and *not* enable it by default

10:15 <re_irc> <@dirbaio:matrix.org> and have the quickstart/template/examples enable it

10:15 <re_irc> <@dirbaio:matrix.org> everyone starts their projects copying from some quickstart

10:16 <re_irc> <@dirbaio:matrix.org> having it enabled by default doesn't gain you much usabiliy

10:18 <re_irc> <@thejpster:matrix.org> But how does an in-tree example enable a feature?

10:19 <re_irc> <@thejpster:matrix.org> Also, can build.rs see the features enabled? I know if can set more features.

10:20 <re_irc> <@dirbaio:matrix.org> thejpster:matrix.org: uhhhh

10:20 <re_irc> <@thejpster:matrix.org> `cargo build --examples` must not fail.

10:20 <re_irc> <@dirbaio:matrix.org> an example can do

10:20 <re_irc> <@dirbaio:matrix.org> [[example]]

10:20 <re_irc> <@dirbaio:matrix.org> ```toml

10:20 <re_irc> <@dirbaio:matrix.org> required-features = ["std", "phy-raw_socket", "proto-ipv4"]

10:20 <re_irc> <@dirbaio:matrix.org> name = "tcpdump"

10:21 <re_irc> <@dirbaio:matrix.org> but I think the example doesn't get built if the features are not enabled

10:21 <re_irc> <@dirbaio:matrix.org> like, `cargo build --examples` won't build it, and `cargo build --example foo` will complain and tell you to add `--features`

10:22 <re_irc> <@dirbaio:matrix.org> IMO in-crate examples don't work for embedded

10:22 <re_irc> <@dirbaio:matrix.org> I just do in-tree examples but in a separate crate, like [this](https://github.com/embassy-rs/embassy/tree/master/examples/nrf)

10:23 <re_irc> <@dirbaio:matrix.org> which is nice because the file structure is now identical to what an end-user crate would do

10:24 <re_irc> <@adamgreig:matrix.org> I've not tried it but can you depend on yourself and add features in dev-dependencies for building examples?

10:24 <re_irc> <@dirbaio:matrix.org> thejpster:matrix.org: `CARGO_FEATURE_FOO` envvar, [docs](https://doc.rust-lang.org/cargo/reference/environment-variables.html#environment-variables-cargo-sets-for-build-scripts)

10:24 <re_irc> <@adamgreig:matrix.org> Separate examples crate that doubles as a template is nice too of course

10:24 <re_irc> <@dirbaio:matrix.org> adamgreig: that seems very cursed, I don't think it works

10:25 <re_irc> <@adamgreig:matrix.org> dev-deps are definitely included for examples and features are unified but yea idk if it's just too cursed

10:25 <re_irc> <@dirbaio:matrix.org> yeah but the "current crate" is included as kind-of a dev-dep automatically so... :S

10:25 <re_irc> <@adamgreig:matrix.org> Yea...

10:26 <re_irc> <@thejpster:matrix.org> OK, I can see that --features=custom-memory-x sets ${CARGO_FEATURE_CUSTOM_MEMORY_X}

10:26 <re_irc> <@thejpster:matrix.org> Throwing out all the in-tree examples I guess isn't impossible. It's a shame though.

10:27 <re_irc> <@dirbaio:matrix.org> they can still be in-tree, you can have multiple crates in the same git repo

10:27 <re_irc> <@thejpster:matrix.org> OK, yes, that's fair.

10:28 <re_irc> <@dirbaio:matrix.org> i'd make the feature `memory-x` and not make it enabled by default

10:28 <re_irc> <@dirbaio:matrix.org> embassy-stm32 does that

10:28 <re_irc> <@dirbaio:matrix.org> not enabling by default avoids some random crate accidentally enabling it by forgetting to add `default-features=false`

10:29 <re_irc> <@dirbaio:matrix.org> have it enabled it in the examples/quickstart and have people copypaste from there

10:29 <re_irc> <@thejpster:matrix.org> But that means moving the examples somewhere that can set the flag

10:30 <re_irc> <@dirbaio:matrix.org> yeah

10:30 <re_irc> <@dirbaio:matrix.org> you'll run into lots of other cursed stuff with in-crate examples anyway

10:47 <re_irc> <@thejpster:matrix.org> such as?

10:49 <re_irc> <@dirbaio:matrix.org> you can't have a build.rs that applies just to the example bins

10:50 <re_irc> <@dirbaio:matrix.org> hm, which is a problem if you want build.rs to drop the memory.x as you would if you didn't have the `memory-x` feature heh

10:51 <re_irc> <@dirbaio:matrix.org> same for `.cargo/config.toml`

10:51 <re_irc> <@dirbaio:matrix.org> and also Cargo feature management is cursed as discussed above

15:12 <re_irc> <@barafael:matrix.org> I've run into issues with in-repo examples before. I'm sure it's partly just a hard problem, but it seems very un-rustic that they are such a hassle

17:54 <re_irc> <@thejpster:matrix.org> This might be more generally applicable, so I'll cross-post it here - I've started work on a crate to support "Binary Info", as supported by Raspberry Pi's `picotool` program.

17:54 <re_irc> <@thejpster:matrix.org> https://github.com/rp-rs/rp-binary-info

17:54 <re_irc> <@thejpster:matrix.org> Might be useful for stuffing version numbers and things into your binaries in a way a tool can easily pull them out of the ELF file.