I am trying to build using cargo build. The following is the project structure
tree
.
├── Cargo.toml
└── src
└── main.rs
The content of Cargo.toml
[package]
name = "server"
version = "0.1.0"
authors = ["Lokanath Mohanty <lokanath.mohanty#adcolony.com>"]
edition = "2018"
# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
[dependencies]
The content of src/main.rs
use std::io::{ErrorKind, Read, Write};
use std::net::TcpListener;
use std::sync::mpsc;
use std::thread;
use std::time::Duration;
const LOCAL_IP: &str = "127.0.0.1:6001";
const MSG_SIZE: usize = 32;
fn main() {
...
}
I am getting the following error -
error: failed to parse manifest at `/home/debashishc/Downloads/Cargo.toml`
Caused by:
no targets specified in the manifest
either src/lib.rs, src/main.rs, a [lib] section, or [[bin]] section must be present
Cargo looks for and tries to parse Cargo.toml in parent directories, because it checks whether your crate is part of a larger workspace.
Remove the broken Cargo.toml from the parent directory. Alternatively, make your crate's Cargo.toml a workspace to stop cargo from searching further.
Related
I am currently learning Rust, and for that purpose I wanted to create my own crate and use it. However, Rust can't find this crate.
I have the following file structure:
├───minimal
│ ├───Cargo.toml
│ └───src
│ └───main.rs
└───util
└───win
├───Cargo.toml
└───src
└───lib.rs
In folder minimal I have my main project. It looks like this:
Cargo.toml
[package]
name = "minimal"
version = "0.1.0"
[dependecies]
win = { path = "../util/win"}
main.rs
extern crate win; // ERROR: "Can't find crate for 'win' rustc(E0463)"
fn main() {
println!("Hello, World!");
}
My library in folder win looks like this:
File Cargo.toml
[package]
name = "win"
version = "0.1.0"
File lib.rs
pub type TestType = String;
My first assumption was that I somehow had a mistake in specifying the path in the dependency of the Cargo.toml file. So I tried to wiggle it around a bit, but it does not seem to work.
Rust reports
can't find crate for 'win' rustc(E0463)
I feel like I am making a very basic error here, however, when looking at similar questions (e.g., How do I "use" or import a local Rust file?) I can't seem to find it.
After having a good night's sleep and looking at this problem again, I have managed to find the error.
I used [dependecies] instead of [dependencies] in the Cargo.toml file.
On the one hand, I feel kind of dumb for this error, but on the other hand I now know that Cargo will not warn about unknown tags in the TOML file.
I need different parts of my project to use different versions of the same extern crate so I'm refactoring my Rust project to be divided into multiple packages via the workspaces system using this as a guide. Doing so is causing all my pub extern crate imports to not work.
This post is very similar to one I created very recently and then deleted - this version contains a minimal, complete, and verifiable example.
Here's my project structure
workspace_test/
root/
src/
main.rs
Cargo.toml
Cargo.toml
workspace_test/Cargo.toml:
[package]
name = "workspace_test"
version = "0.1.0"
authors = ["Phoenix <kahlo.phoenix#gmail.com>"]
[workspace]
members = [
"root"
]
[[bin]]
name = "root"
path = "root/src/main.rs"
workspace_test/root/Cargo.toml:
[package]
name = "root"
version = "0.1.0"
authors = ["Phoenix <kahlo.phoenix#gmail.com>"]
[dependencies]
time = "0.1"
workspace_test/root/src/main.rs:
pub extern crate time;
fn main() {
println!("Hello, world!");
}
This is also on github, so it can easily be cloned and cargo run'd.
This is the error:
error[E0463]: can't find crate for `time`
--> root/src/main.rs:1:1
|
1 | pub extern crate time;
| ^^^^^^^^^^^^^^^^^^^^^^ can't find crate
error: aborting due to previous error
error: Could not compile `workspace_test`.
In workspace_test/Cargo.toml you create a package with the binary root. If you execute cargo run, it runs the main.rs, but since you didn't state the dependencies in this manifest file, the error occurs. The dependency is only specified in workspace_test/root/Cargo.toml, which is not used at this point.
I assume you want to use the workspaces proposed by the RFC. You can create a workspace with virtual manifests, which must neither specify a [package] nor [[bin]], so just remove them. workspace_test/Cargo.toml now looks like this:
[workspace]
members = [
"root"
]
If you only have one executable, you can now pass the package: -p/--package
cargo run -p root
or specify the manifest path manually:
cargo run --manifest-path root/Cargo.toml
If root/Cargo.toml contains multiple targets, you can just append the --lib or --bin flags as usual. E.g. this would execute the abc-binary specified in workspace_test/root/Cargo.toml:
cargo run -p root --bin abc
I have a crate that is imported straight off of GitHub, as per Cargo's documentation:
[dependencies]
libfoo = { git = "ssh://git#github.com/me/libfoo", branch = "dev" }
[lib]
path = "src/rust/lib.rs"
name = "myprj"
crate-type = ["cdylib"]
Running cargo build works fine here, Cargo fetches libfoo and builds it in the ~/.cargo directory. When I try to use (import) it in lib.rs:
extern crate libfoo; //also tried foo
Cargo chokes:
error[E0463]: can't find crate for `libfoo`
--> src/rust/lib.rs:1:1
|
1 | extern crate libfoo;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^ can't find crate
Interestingly, IntelliJ's Rust plugin does find the crate when I click on it in lib.rs – it navigates to the downloaded source in ~/.cargo...
In the dependency libfoo, the lib section of the Cargo.toml file is specified as:
[package]
name = "libfoo"
[lib]
name = "foo"
crate-type = ["cdylib"]
I have tried all permutations of libfoo and foo to see if Cargo is getting confused between the lib name and the package/directory name.
It also fails if I specify a local path to the dependency. (Cargo compiles the dependency but then claims not to find it when it is declared/imported in lib.rs.)
[dependencies]
libfoo = { path = "/Users/me/dev/libfoo" }
If I include a crate from git or the file system that has the same [lib] name as the [package] name, it works fine. So it appears the problem is with crates that have a have a library ([lib]) name that is different from the package ([package]) name.
If I remove the [lib] section from the dependency's Cargo.toml file, it works.
Update: if crate-type = ["cdylib"] is removed from libfoo, this works with foo imported. If that is there, I get the same error with extern crate foo;.
Cargo is interested in package names when it comes to dependencies, while the compiler (rustc) is interested in library names when it comes to loading their metadata and linking with them.
Let's take a look again at this Cargo.toml excerpt:
[package]
name = "libfoo"
[lib]
name = "foo"
Here, the package name is libfoo and the library name is foo.
When you want to declare a dependency on libfoo in your project, you need to write the package name (libfoo) in the [dependencies] table. For example:
[dependencies]
libfoo = { git = "ssh://git#github.com/me/libfoo", branch = "dev" }
This is what you already have, and it's correct.
However, when you want to import the library in your crate, you need to write the library name in the extern crate item, i.e.
extern crate foo;
How did I figure this out? First, I wrote libfoo in both Cargo.toml and the extern crate item, as you described. When I ran cargo build, I noticed that libfoo was built successfully, indicating that Cargo correctly resolved the dependency. But I also noticed that the compiler couldn't find libfoo, as you experienced.
I then inspected the command line passed to rustc by running cargo build --verbose. This is what I saw (irrelevant parts omitted):
Running `rustc [...] --extern foo=/[path]/target/debug/deps/libfoo-5cf876c5c8ac1bfb.rlib`
The --extern name=path argument tells rustc that the crate named name is located in path. The name here is foo, so we must write extern crate foo; in the code to reference it.
I have a crate with both src/lib.rs and src/main.rs.
main.rs is just using extern crate programname (which is lib.rs) and uses certain functions from lib.rs and it's submodules.
The documentation on linking says:
Pure-Rust dependencies are statically linked by default so you can use created binaries and libraries without installing Rust everywhere.
How can I change this behavior so a binary created from main.rs will be dynamically linked to library produced by lib.rs?
I've added the following to Cargo.toml
[lib]
path = "src/lib.rs"
crate-type = ["dylib"]
[[bin]]
name = "programname"
path = "src/main.rs"
But it does not compile and gives me errors like:
error: cannot satisfy dependencies so `std` only shows up once
help: having upstream crates all available in one format will likely make this go away
If I add "rlib" to lib section, it compiles, but the binary is not linked against libprogramname.so
I try to compile my project with the command cargo build.
build.rs
extern crate csv;
use std::path::Path;
use std::fs::OpenOptions;
use std::io::BufWriter;
use std::io::Write;
#[allow(non_snake_case)]
fn processCSV(filename: &str, sourcePath: &str, enumName: &str) {
println!("Generate rust source code from schema {}",filename);
let mut ret: Vec<String> = Vec::new();
let mut rdr = csv::Reader::from_file(filename).unwrap().flexible(true);
for record in rdr.records().map(|r| r.unwrap()) {
}
let path = Path::new(sourcePath);
let file = match OpenOptions::new().write(true).create(true).open(&path) {
Ok(file) => file,
Err(..) => panic!("Cannot create file {}",path.display()),
};
let mut writer = BufWriter::new(file);
writer.write_all(b"test\n");
}
fn main() {
processCSV("../schemas/Test.csv", "./src/mod/common/StatusCode.rs", "StatusCode");
}
and Cargo.toml
[package]
name = "rust-test"
version = "0.0.1"
build = "build.rs"
[lib]
path = "src/lib.rs"
[dependencies]
[build-dependencies]
csv = "*"
I can see this error :
src/lib.rs:1:1: 1:18 error: can't find crate for csv
src/lib.rs:1 extern crate csv;
but when I change flexible(true) to flexible(false) it compiles just fine without any errors. What do I need to do to fix this?
I am using Rust 1.2.0 on Windows 7 64-bit.
Changing flexible(false) for flexible(true) makes no difference for me; both fail. The problem is that you've chosen build-dependencies for some reason, instead of just dependencies.
Using the src/lib.rs file that you provided in your answer, and this Cargo.toml file:
[package]
name = "stack-overflow"
version = "0.1.0"
authors = ["A. Developer <a.developer#example.com>"]
[dependencies]
csv = "*"
It compiles fine.
If you need to access a dependency both in your build.rs and in your project, you need to include the dependency in both sections.
A build dependency is a dependency for a build script, which is a helper binary compiled and run before your main crate is built (designed to be used for code-generation, and building/finding native C libraries, etc.).
Normal dependencies used by the main code should just fall into the "dependencies" section, e.g.
[dependencies]
csv = "0.14"
There's also a "dev-dependencies" section, which are dependencies that are only needed for testing, i.e. they are compiled and used only for cargo test. This allows crates to depend on, for example, quickcheck for running tests without contaminating the main artifact.
In summary, running cargo build will do something like:
build any build-dependencies
build the build script (pointing the compiler to the built build-dependencies), and run it
build any dependencies
build the main crate (pointing the compiler to the built dependencies)
Running cargo test adds:
build any dev-dependencies
build the main crate with --test to create a test runner for any in-source #[test]s (pointing the compiler to both the dependencies and dev-dependencies)
build any external examples or tests, also pointing to both the dependencies and dev-dependencies