crypto_box: select x25519-dalek backend automatically

[tarcieri]

Introspects the target pointer width to automatically select either the u32_backend or u64_backend.

If the backend isn't 32/64-bit, generate a compile error with an informative message.

Removes the explicit u32_backend/u64_backend crate features in cargo_box itself. Now --all-features works.

[kurnevsky]

Does this work when crypto_box is used as dependency (just adding crypto_box = "0.8")? It doesn't compile for me because for some reason u32_backend is enabled even though I have 64 bit architecture (which produces a lot of compilation errors).

[trevyn]

I can also reproduce this, but I haven’t had a chance to fully debug what is going on.

[tarcieri]

Sorry to hear this is causing issues. I can revert it. It would be great to get some more information about the error you're encountering though.

I can see how it might be an issue on 32-bit platforms, since u64_backend is enabled per default, and enabling two backends at once causes pages of compile errors, which you might encounter if you have another crate that also links curve25519-dalek. Is that what you're encountering?

FWIW, it builds on two 32-bit targets in CI. And I just pushed up a PR that adds full cross tests: #62

[trevyn]

Here's the errors: https://github.com/trevyn/sealed_box/runs/7829889187

% cargo tree -i curve25519-dalek
curve25519-dalek v3.2.0
└── x25519-dalek v1.1.1
    └── crypto_box v0.8.0
        └── sealed_box v0.1.1 (/Users/e/Documents/GitHub/sealed_box)

[tarcieri]

Yeah, that looks like two backends were activated at the same time. Is there not another dependency that uses curve25519-dalek?

Regardless I guess this doesn't work because other dependencies may activate a different backend so fine-grained control is needed to match.

[kurnevsky]

Yeah, that looks like two backends were activated at the same time. Is there not another dependency that uses curve25519-dalek?

Yes, the only dependency I add is crypto_box = "0.8". Here is the cargo tree:

tox_crypto v0.1.1 (/home/kurnevsky/workspace/tox/tox_crypto)
└── crypto_box v0.8.0
    ├── aead v0.5.1
    │   ├── crypto-common v0.1.6
    │   │   ├── generic-array v0.14.6
    │   │   │   └── typenum v1.15.0
    │   │   │   [build-dependencies]
    │   │   │   └── version_check v0.9.4
    │   │   ├── rand_core v0.6.3
    │   │   │   └── getrandom v0.2.7
    │   │   │       ├── cfg-if v1.0.0
    │   │   │       └── libc v0.2.131
    │   │   └── typenum v1.15.0
    │   └── generic-array v0.14.6 (*)
    ├── chacha20 v0.9.0
    │   ├── cfg-if v1.0.0
    │   ├── cipher v0.4.3
    │   │   ├── crypto-common v0.1.6 (*)
    │   │   ├── inout v0.1.3
    │   │   │   └── generic-array v0.14.6 (*)
    │   │   └── zeroize v1.5.7
    │   │       └── zeroize_derive v1.3.2 (proc-macro)
    │   │           ├── proc-macro2 v1.0.43
    │   │           │   └── unicode-ident v1.0.3
    │   │           ├── quote v1.0.21
    │   │           │   └── proc-macro2 v1.0.43 (*)
    │   │           ├── syn v1.0.99
    │   │           │   ├── proc-macro2 v1.0.43 (*)
    │   │           │   ├── quote v1.0.21 (*)
    │   │           │   └── unicode-ident v1.0.3
    │   │           └── synstructure v0.12.6
    │   │               ├── proc-macro2 v1.0.43 (*)
    │   │               ├── quote v1.0.21 (*)
    │   │               ├── syn v1.0.99 (*)
    │   │               └── unicode-xid v0.2.3
    │   └── cpufeatures v0.2.2
    ├── chacha20poly1305 v0.10.1
    │   ├── aead v0.5.1 (*)
    │   ├── chacha20 v0.9.0 (*)
    │   ├── cipher v0.4.3 (*)
    │   ├── poly1305 v0.8.0
    │   │   ├── cpufeatures v0.2.2
    │   │   ├── opaque-debug v0.3.0
    │   │   └── universal-hash v0.5.0
    │   │       ├── crypto-common v0.1.6 (*)
    │   │       └── subtle v2.4.1
    │   └── zeroize v1.5.7 (*)
    ├── salsa20 v0.10.2
    │   └── cipher v0.4.3 (*)
    ├── x25519-dalek v1.1.1
    │   ├── curve25519-dalek v3.2.0
    │   │   ├── byteorder v1.4.3
    │   │   ├── digest v0.9.0
    │   │   │   └── generic-array v0.14.6 (*)
    │   │   ├── rand_core v0.5.1
    │   │   ├── subtle v2.4.1
    │   │   └── zeroize v1.5.7 (*)
    │   ├── rand_core v0.5.1
    │   └── zeroize v1.5.7 (*)
    ├── xsalsa20poly1305 v0.9.0
    │   ├── aead v0.5.1 (*)
    │   ├── poly1305 v0.8.0 (*)
    │   ├── salsa20 v0.10.2 (*)
    │   ├── subtle v2.4.1
    │   └── zeroize v1.5.7 (*)
    └── zeroize v1.5.7 (*)

Regardless I guess this doesn't work because other dependencies may activate a different backend so fine-grained control is needed to match.

So it's not the case :)

[kurnevsky]

It seems it wasn't supposed to work in cargo: rust-lang/cargo#10053

[tarcieri]

PR to revert these changes here: #63

[tarcieri]

crypto_box v0.8.1 has been released with this PR reverted