Context:
I have a local C library called 'libmaths' that then uses Bindgen to create a 'libmaths-sys' crate that is locally stored in the same directory as my project.
Issue:
I want to use some of the features in the 2021 edition of Rust and currently my project is built off 2018. I am trying to update the project by following the instructions at:
https://doc.rust-lang.org/cargo/commands/cargo-fix.html
Run cargo fix --edition. Consider also using the --all-features flag if your project has multiple features. You may also want to run cargo
fix --edition multiple times with different --target flags if your
project has platform-specific code gated by cfg attributes.
Modify Cargo.toml to set the edition field to the new edition.
Run your project tests to verify that everything still works. If new
warnings are issued, you may want to consider running cargo fix again
(without the --edition flag) to apply any suggestions given by the
compiler.
To run cargo fix --edition I am told by the compiler to remove the edition="2018" in cargo toml. Following this I receive a compile error stating that libmaths-sys cannot be found. The code compiles and executes normally in 2018 but not without this edition tag.
I can not find anyone with a similar issue, this is my first stackoverflow question so not sure how best to show my code given its a context of a small project.
Error code
error[E0432]: unresolved import `libmaths_sys`
--> src/main.rs:1:5
|
1 | use libmaths_sys::*; // lib.rs in sys crate
| ^^^^^^^^^^^^ maybe a missing crate `libmaths_sys`?
File Structure and general overview of project
.
├── Cargo.lock
├── Cargo.toml
├── libmaths
│ ├── add.c
│ ├── add.h
│ └── subtract.c
├── libmaths-sys
│ ├── build.rs
│ ├── Cargo.lock
│ ├── Cargo.toml
│ ├── src
│ │ └── lib.rs
│ └── wrapper.h
├── README.md
└── src
├── lib.rs
└── main.rs
libmaths contains add.c that returns a + b and subtract.c which returns a - b, with a header add.h directing to both .c files
The Rust code generated by bindgen is attached via lib.rs in the libmath-sys crate which links to the OUT DIR which I have omitted from the tree to save 200 lines of file names.
Try updating edition="2018" to edition="2021"; otherwise it defaults to edition="2015" which requires usage of extern crate.
As #Solomon Ucko directed me to, rustup update held the key.
Running rustup update produced:
info: syncing channel updates for 'stable-x86_64-unknown-linux-gnu'
info: syncing channel updates for '1.48-x86_64-unknown-linux-gnu'
info: checking for self-updates
stable-x86_64-unknown-linux-gnu unchanged - rustc 1.59.0 (9d1b2106e 2022-02-23)
1.48-x86_64-unknown-linux-gnu unchanged - rustc 1.48.0 (7eac88abb 2020-11-16)
info: cleaning up downloads & tmp directories
In the end, rustup was using the old 1.48 version and not the installed 1.59 version.
To switch to the newer vesion I ran:
rustup default stable
I then could follow the instructions from the link in the original question to change the edition.
Related
I have a Cargo workspaces project with the structure:
├── src
├── lib
│ └── Cargo.toml
├── tools
│ ├── src/bin/foo.rs
│ └── Cargo.toml
└── Cargo.toml
., lib and tools are my three workspace members. lib has a feature that enables tracing of the execution of a performance-sensitive function. As this feature adds performance overhead, the main binary should not enable it, but the foo binary is a testing tool which uses it.
However, Cargo workspaces take the union of the features of the two binaries, so the main binary ends up including the feature anyway.
How can I fix this?
I am developing a code for my school's rocketry team and I have two programs, one meant to flash the on-board computer and another to run some data analysis on the flight data. The chip code uses no_std while the data analysis program uses std. The data-analysis code will run on my PC, and the chip code will run on the chip.
Here is my workspace root Cargo.toml and my project graph:
[workspace]
members = [
"chip",
"data-analysis",
]
.
├── Cargo.lock
├── Cargo.toml
├── chip
│ ├── Cargo.toml
│ ├── memory.x
│ ├── openocd.cfg
│ ├── openocd.gdb
│ └── src
│ └── main.rs
├── data-analysis
│ ├── Cargo.toml
│ └── src
│ └── main.rs
├── README.md
└── resources
├── 3m.mkd
├── data-stm32f103c8t6.pdf
├── links.txt
├── reference-stm32f103xx.pdf
├── schematic-stm32f103c8t6.png
└── todo.txt
I have decided to use a workspace to organize my code. When I attempt to build the workspace, I get the error:
error[E0463]: can't find crate for `std`
|
= note: the `thumbv7m-none-eabi` target may not support the standard library
= note: `std` is required by `data_analysis` because it does not declare `#![no_std]`
= help: consider building the standard library from source with `cargo build -Zbuild-std`
When I compile with cargo build -Zbuild-std I get the error:
error[E0463]: can't find crate for `panic_abort`
error[E0658]: use of unstable library feature 'restricted_std'
|
= help: add `#![feature(restricted_std)]` to the crate attributes to enable
However I need no_std and not restricted_std.
I understand that dependencies for all files are stored in Cargo.lock and presumably that's why it is producing this error. My question is, how do I express to the compiler that I need std for data_analysis but not for chip code? Should I even be using workspaces over just using one package with multiple binaries and using [features] in the Cargo.toml?
It seems like you're trying to complile data_analysis with the same target as chip. I recommend just getting rid of the root Cargo.toml and compiling the respective ones in the folders. You could make a Makefile to automate this easily
This question already has an answer here:
What is the difference between library crates and normal crates in Rust?
(1 answer)
Closed 2 years ago.
What's the difference between binary and library in Rust?
I read The Cargo Book, but couldn't understand it well.
I generated two folders using cargo new a --bin and cargo new b --lib, however, both of them look the same inside. What are the purposes of --bin and --lib? And what are the difference between them?
A binary crate should generate an executable (or multiple) that can be installed in the user's path and can be executed as usual.
The purpose of a library crate on the other hand is not to create executables but rather provide functionality for other crates to depend on and use.
Also they do differ in their structure:
✦2 at [22:50:27] ➜ cargo new --bin somebinary
✦2 at [22:50:29] ➜ cargo new --lib somelib
Created library `somelib` package
✦2 at [22:50:34] ➜ tree somebinary/
somebinary/
├── Cargo.toml
└── src
└── main.rs
1 directory, 2 files
✦2 at [22:50:41] ➜ tree somelib/
somelib/
├── Cargo.toml
└── src
└── lib.rs
You can also find more information in this rust-lang forum thread: https://users.rust-lang.org/t/what-is-the-difference-between-cargo-new-lib-and-cargo-new-bin/19009
One creates an src/main.rs and other creates src/lib.rs. They are different in the nature of the files which are created. Differences lies in whether you are interested in creating a library or interested in creating a binary
Are you sure you ran those exact same commands?
(ins)temp->tree
.
├── a
│ ├── Cargo.toml
│ └── src
│ └── main.rs
└── b
├── Cargo.toml
└── src
└── lib.rs
I have a barebones workspace project:
.
├── build-debug.sh
├── Cargo.lock
├── Cargo.toml
├── common
│ ├── Cargo.toml
│ └── src
│ └── lib.rs
├── rs-test.iml
├── server
│ ├── Cargo.toml
│ └── src
│ └── main.rs
└── wui
├── Cargo.toml
└── src
└── lib.rs
The rs files either empty or just an empty main function.
The server and the wui depends on common: common = { path = "../common" }.
The common project has one crates.io dependency with I suppose build script or proc macro dependency.
The build script:
cargo build -p wui --target wasm32-unknown-unknown
cargo build -p server
The problem:
When I rebuild the unchanged project, some wui dependencies are getting invalidated/rebuilt, then the same for server.
Either:
remove the wasm32 target flag
replace the dependency with a simple crate without build time compiled dependencies
It does not rebuild the subprojects anymore.
Is this a cargo bug? What can I do?
It's probably not a cargo bug. What is likely happening here is that your crates.io dependency (you don't mention what it is, which might have been useful) has different dependencies or features depending on the target architecture. Thus, as you alternate between building the WASM target and your host target, stuff is being rebuilt.
Perhaps it would be better in this case to stop using the Cargo workspace and build the server and wui separately; this way you'll have separate target directories for the server and wui, which takes some extra disk space and takes longer for non-incremental compilation, but will prevent you from having to rebuild that stuff all the time as you build both.
Where should one put the sources, examples, documentation, unit tests, integration tests, license, benchmarks etc?
Cargo, the official package manager for Rust, defines some conventions regarding the layout of a Rust crate:
.
├── Cargo.lock
├── Cargo.toml
├── benches
│ └── large-input.rs
├── examples
│ └── simple.rs
├── src
│ ├── bin
│ │ └── another_executable.rs
│ ├── lib.rs
│ └── main.rs
└── tests
└── some-integration-tests.rs
Cargo.toml and Cargo.lock are stored in the root of your project.
Source code goes in the src directory.
The default library file is src/lib.rs.
The default executable file is src/main.rs.
Other executables can be placed in src/bin/*.rs.
Integration tests go in the tests directory (unit tests go in each file they're testing).
Example executable files go in the examples directory.
Benchmarks go in the benches directory.
These are explained in more detail in the manifest description.
By following this standard layout, you'll be able to use Cargo's commands to build, run and test your project easily. Run cargo new to set up a new executable project or cargo new --lib to set up a new library project.
Additionally, documentation for libraries is often written in documentation comments (comments that start with /// before any item, or //! to document the parent item). Also, the license is usually put at the root.
Unit tests, as mentioned above, are written in the same module as the functions they're testing. Usually, they're put in an inner module. It looks like this (this is what Cargo generates for a new library with cargo new --lib):
#[cfg(test)]
mod tests {
#[test]
fn it_works() {
}
}