Cargo Run Redundancy | Generated by AI

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You’re absolutely correct! In your Makefile example:

run:
	cargo build
	cargo run

Including cargo build before cargo run is redundant because cargo run already includes the build step. When you execute cargo run, Cargo automatically checks if the project needs to be rebuilt (e.g., if source files have changed) and, if necessary, compiles the project before running the resulting binary. This makes the explicit cargo build step unnecessary in this context.

Clarification

• cargo run:
  • Combines cargo build (compiles the project into target/debug/<project_name>) and then runs the binary.
  • Only rebuilds if there are changes in the source code or dependencies.
• cargo build:
  • Only compiles the project without running the binary.
  • Useful if you want to verify compilation without executing the program.

Fixing the Makefile

To streamline your Makefile, you can remove the redundant cargo build:

run:
	cargo run

This achieves the same result: the project is built (if needed) and then executed.

When to Use cargo build Separately

You might want to keep cargo build as a separate target in the Makefile for cases where you only want to compile without running, such as:

• Checking for compilation errors.
• Preparing binaries for deployment or testing without execution.

For example:

build:
	cargo build

run:
	cargo run

clean:
	cargo clean

• Run make build to compile only.
• Run make run to build (if needed) and run.
• Run make clean to clear build artifacts.

Addressing Your Previous Context

Since you’re working with a Rust project where main.rs calls run_simple from simple.rs, ensure the privacy error (E0603) is resolved by making run_simple public in src/simple.rs:

pub fn run_simple() {
    println!("Hello from run_simple!");
}

And in src/main.rs:

mod simple;

fn main() {
    simple::run_simple();
}

Also, update Cargo.toml to remove the edition2024 warning, as discussed earlier:

[package]
name = "example"
version = "0.1.0"
edition = "2024"

Testing the Setup

1. Update the Makefile as shown above.
2. Run:

   make run
   

   This will execute cargo run, which builds (if needed) and runs the program, printing Hello from run_simple! (or whatever output run_simple produces).

3. If you want to verify compilation separately:

   make build
   

Additional Notes

• If you’re using cargo run --bin simple (for a separate binary in simple.rs), ensure Cargo.toml includes:

  [[bin]]
  name = "simple"
  path = "src/simple.rs"
  

  And simple.rs has a main function:

  pub fn run_simple() {
      println!("Hello from run_simple!");
  }
  
  fn main() {
      run_simple();
  }
  

• If you encounter issues, share the output of make run or cargo run for further debugging.

Final Makefile Recommendation

build:
	cargo build

run:
	cargo run

clean:
	cargo clean

This setup avoids redundancy, supports both building and running, and keeps your workflow clean. Let me know if you have more questions or need help with specific errors!

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