I have just started looking into the Bevy game engine for Rust. It has a feature called dynamic, which enables dynamic linking, to speed up compilation time during development. We are, however, advised to disable this when building for release.
Is there a way to tell Cargo to enable the dynamic feature for a debug build, but disable it for a release build? Or do I have to personally remember to change bevy = { version = "0.5.0", features = ["dynamic"] } to bevy = "0.5.0" in Cargo.toml before running cargo build --release?
Along the lines of Rodrigo's comment, can confirm the following seems to work well:
[dependencies]
bevy = { version = "0.5.0" }
[features]
default = ["fast-compile"]
fast-compile = ["bevy/dynamic"]
Then for development, simply: cargo build
And for release: cargo build --release --no-default-features
Related
Windows 10
rustup 1.23.1 (3df2264a9 2020-11-30)
default rustc 1.50.0 (cb75ad5db 2021-02-10)
project rustc 1.52.0-nightly (4a8b6f708 2021-03-11)
rocket = "0.4.4"
I'm trying to build a rust project with rocket but I always get this error when compiling, even after successfully overwriting the project's toolchain:
D:\GitHub\Learning-Rust\poke_api> rustup override set nightly
info: using existing install for 'nightly-x86_64-pc-windows-msvc'
info: override toolchain for 'D:\GitHub\Learning-Rust\poke_api' set to 'nightly-x86_64-pc-windows-msvc'
nightly-x86_64-pc-windows-msvc unchanged - rustc 1.52.0-nightly (4a8b6f708 2021-03-11)
PS D:\GitHub\Learning-Rust\poke_api> cargo build
Compiling winapi v0.3.9
Compiling serde_derive v1.0.124
Compiling rocket v0.4.7
Compiling pear_codegen v0.1.4
Compiling rocket_codegen v0.4.7
Compiling proc-macro2 v1.0.24
Compiling pq-sys v0.4.6
Compiling aho-corasick v0.6.10
Compiling serde_json v1.0.64
error: failed to run custom build command for `pear_codegen v0.1.4`
Caused by:
process didn't exit successfully: `D:\GitHub\Learning-Rust\poke_api\target\debug\build\pear_codegen-e182711746033ac9\build-script-build` (exit code: 101)
--- stderr
Error: Pear requires a 'dev' or 'nightly' version of rustc.
Installed version: 1.48.0 (2020-11-16)
Minimum required: 1.31.0-nightly (2018-10-05)
thread 'main' panicked at 'Aborting compilation due to incompatible compiler.', C:\Users\gabre\.cargo\registry\src\github.com-1ecc6299db9ec823\pear_codegen-0.1.4\build.rs:24:13
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
warning: build failed, waiting for other jobs to finish...
error: build failed
I had a similar issue while using rocket. Same error message too, Error: Pear requires a 'dev' or 'nightly' version of rustc.
If you get to the get-started page on rocket framework website. It says, "Rocket makes abundant use of Rust's syntax extensions and other advanced, unstable features. Because of this, we'll need to use a nightly version of Rust."
My issue was I was not using a nightly version of rust. Running this on my terminal in my project directory did it for me.
rustup override set nightly
If you check the cargo version for that directory after,
cargo version
you will confirm it has switched to nightly version
Failed compilation even with nightly
It looks like you have some outdated dependencies (pear-codegen probably being the one that causes trouble), updating these may resolve the compilation issues.
General notes on how to override the toolchain
Using rustups override works fine, but it is bound to your local rustup configuration and not specified inside the project.
In order to achieve this, thereby making the project more portable and allowing others to always use the correct toolchain, I would recommend the toolchain file. It can look something like this (example taken from linked page) and will accurately specify the required toolchain only for the containing project.
# rust-toolchain.toml
[toolchain]
channel = "nightly-2020-07-10"
components = [ "rustfmt", "rustc-dev" ]
targets = [ "wasm32-unknown-unknown", "thumbv2-none-eabi" ]
profile = "minimal"
For your purposes a simple configuration like this will most likely be all you need, although adding the components you want to use would be beneficial.
[toolchain]
channel = "nightly"
My issue was with rust-analyser that wouldn't start because multiple rocket dependencies needed nightly or dev version of rustc.
These steps fixed my issue:
Switch to nightly for my rocket project by running rustup override set nightly inside the app folder.
Remove all target folders in my project. (I also had one in root)
Manually remove the faulty cached packages from cargo cache. cd ~/.cargo/registry/cache/github.com-xxxxxxxxxxxx && rm -r pear_codegen-0.1.5/
I am using some Rust unstable features, but I still want to be able to compile a reduced version of my library with stable Rust. I am happy to only include those unstable features when the compiler supports them, and exclude them when they are not supported.
I thought it would be easy to achieve this goal using conditional compilation like #[cfg(rust_version = "nightly")], but it seems like 'stable' vs 'nightly' are not cfg options.
How do you guys perform conditional compilation based on 'stable' vs 'nightly', or based on the compiler version?
I recommend creating a feature for your nightly-only code that is disabled by default, for example
Cargo.toml
[features]
default = []
nightly-features = []
Since the nightly-features feature is not default, compilation with the stable toolchain works out of the box. You can use attributes #[cfg(feature = "nightly-features")] and #[cfg(not(feature = "nightly-features"))] to include or exclude code from nightly-specialized versions. This method has the added benefit of allowing testing of the nightly features independently of the compiler (i.e. answer the question: did the compiler break my code, or does code enabled by nightly-features contain bugs?).
Despite the risks, I want to enable nightly features automatically
Use build scripts, sometimes called build.rs in addition to the nightly feature described above. (note: the following should NEVER be used in a library, otherwise switching compilers could become a breaking change. prefer the solution explained above)
build.rs (goes in package root)
use std::env;
fn main() {
let rust_toolchain = env::var("RUSTUP_TOOLCHAIN").unwrap();
if rust_toolchain.starts_with("stable") {
// do nothing
} else if rust_toolchain.starts_with("nightly") {
//enable the 'nightly-features' feature flag
println!("cargo:rustc-cfg=feature=\"nightly-features\"");
} else {
panic!("Unexpected value for rustc toolchain")
}
}
this build script checks the toolchain environment variable set by rustup (some rust installations do not use rustup) and enables the nightly feature flag if the compiler is nightly.
src/main.rs
fn main() {
#[cfg(feature = "nightly-features")]
println!("Hello, nightly!");
#[cfg(not(feature = "nightly-features"))]
println!("Hello, stable!");
}
now, running
➜ cargo +stable run
Hello, stable!
➜ cargo +nightly run
Hello, nightly!
Is it possible to turn this feature off when build.rs turns it on?
As far as I can tell, no. Running cargo +nightly run --no-default-features leaves the feature on, due to how cargo passes flags to rustc. A programmer could create a specific environmental variable that build.rs checks for to skip the automatic version detection, but that is more complicated than the alternative with no build script - cargo build --features=nightly-features
Crate alternative
Instead of the proposed solution, you can use the rustversion crate, which works in a very similar way (but parses the output of rustc --version).
fn main() {
#[rustversion(nightly)]
println!("Hello, nightly!");
#[rustversion::not(nightly)]
println!("Hello, stable! (or beta)");
}
I have the following dependency configuration in Cargo.toml.
[dependencies.ffmpeg-sys]
version = "3.4.1"
default-features = false
features = ["avcodec", "avformat", "swresample", "static", "build"]
Adding the build feature hugely increases compile time and I only need to do it when building in release mode.
Is there a way to disable features of a dependency based on the build type (debug, release, RLS)?
I often want to compile in release mode with debug = true so that I can read the generated assembly a bit easier. I am currently doing this:
[profile.release]
debug = true
but I don't want any debug symbols in my final release build. I'd like to do something like:
[profile.custom]
debug = true
opt-level = 3
rpath = false
lto = true
debug-assertions = false
codegen-units = 1
panic = 'unwind'
And then run
cargo build --custom
I've read the documentation to no avail.
As of Rust v1.57.0, the custom profiles feature is now stable.
Add a profile section, specify a base profile to inherit from, and tweak as you see fit:
[profile.production]
inherits = "release"
lto = true
Specify the profile to use via the --profile <name> flag to cargo.
Does Cargo support custom profiles?
No, stable releases of Cargo do not support this. It is available as an unstable nightly feature.
If you are using a nightly version of Cargo, you can create custom profiles in your Cargo.toml:
cargo-features = ["named-profiles"]
[profile.release-lto]
inherits = "release"
lto = true
And then use them:
cargo +nightly build --profile release-lto -Z unstable-options
I want to conditionally compile my source code using cfg with Cargo,
after Googling for a while,
it seems that the solution is to use cargo --features.
http://doc.crates.io/manifest.html
I tried adding a few
#[cfg(feature = "foo")]
in the source code and
cargo build --features foo
, but it says
Package `xxx v0.0.1 (file:///C:/yyy/xxx)` does not have these features: `foo`
How can I let cargo identify the features? Do I have to add something in Cargo.toml?
Here's the version of rustc and cargo I am using:
C:\>rustc --version
rustc 0.13.0-nightly (42deaa5e4 2014-12-16 17:51:23 +0000)
C:\>cargo --version
cargo 0.0.1-pre-nightly (5af754d 2014-12-18 01:50:48 +0000)
You have to introduce the existing features in your Cargo.toml.
I was able to conditionally compile by doing the following:
In Cargo.toml, create a features section and introduce a certain feature name:
[features]
customfeature = [] # feature has no explicit dependencies
If you want your feature to have specific dependencies check the examples in the documentation.
In your code, use #[cfg(feature="customfeature")]
Run cargo build --features customfeature
Since your steps 2 & 3 seem to be fine, there must probably be a problem with your Cargo.toml.
As stated in other answers, you can use features for this. I would like to add that features do not only allow you to conditionally compile parts of your code but also to conditionally include dependencies that may be part of that code. Consider the following snippets:
You can activate the conditional code using a feature flag as already described in other anwsers:
cargo build --features customfeature
You need to mark your conditional code to exist only when your customfeature is enabled:
#[cfg(feature = "customfeature")]
fn my_func() {
my_optional_dependency::do_something();
}
// This includes dependencies only when customfeature is enabled
#[cfg(feature = "customfeature")]
extern crate my_optional_dependency;
....
#[cfg(feature = "customfeature")]
use my_optional_dependency::*;
....
Your Cargo.toml needs to have the following sections:
[dependencies.my_optional_dependency]
version = "1.2.3"
optional = true
[features]
customfeature = ["my_optional_dependency"]
This allows you to activate certain parts of your code along with their dependencies only if a feature is enabled.
Alternatively, you could create a cargo configuration file in your project, by creating a .cargo subdir in your project main folder, adding in it a config.toml file,
then inserting this section in .cargo/config.toml:
[build]
rustflags = "--cfg my_cfg_flag"
This will make cargo call rustc with flags --cfg my_cfg_flag
See here for details:
https://doc.rust-lang.org/cargo/reference/config.html