Cross-Compilation Toolchain Generator in Rust

Cross-compilation allows you to build executables for a different target architecture than the one you're currently using. This is crucial for embedded systems, deploying to different operating systems, or creating binaries for various hardware platforms. This challenge asks you to build a simple tool in Rust that generates a basic cross-compilation toolchain configuration file (specifically, a config.toml file suitable for use with cargo build --target).

Problem Description

You are tasked with creating a Rust program that takes a target architecture as input and generates a config.toml file containing the necessary configuration for cargo to cross-compile for that target. The program should accept the target architecture as a command-line argument. The generated config.toml file should include the target setting and a basic linker setting. The program should handle invalid target architectures gracefully.

What needs to be achieved:

• Accept a target architecture string as a command-line argument.
• Validate the provided target architecture against a predefined list of supported targets.
• Generate a config.toml file with the target and linker settings based on the provided target.
• Handle invalid target architectures by printing an error message to standard error and exiting with a non-zero exit code.

Key Requirements:

• The program must be written in Rust.
• The generated config.toml file must be valid TOML.
• The program must handle command-line arguments correctly.
• The program must provide informative error messages.

Expected Behavior:

When executed with a valid target architecture, the program should create a config.toml file in the current directory with the correct settings. When executed with an invalid target architecture, the program should print an error message to standard error and exit with a non-zero exit code.

Edge Cases to Consider:

• Invalid target architecture strings (e.g., typos, unsupported architectures).
• Missing command-line arguments.
• File writing errors (e.g., insufficient permissions).
• Empty target architecture string.

Examples

Example 1:

Input: ./cross_compiler_generator --target x86_64-unknown-linux-gnu
Output: (Creates a file named config.toml in the current directory with the following content)
```toml
target = "x86_64-unknown-linux-gnu"
linker = "lld"

Explanation: The program successfully generated a config.toml file for the specified target.

Example 2:

Input: ./cross_compiler_generator --target arm-unknown-linux-musl
Output: (Creates a file named config.toml in the current directory with the following content)
```toml
target = "arm-unknown-linux-musl"
linker = "lld"

Explanation: The program successfully generated a config.toml file for the specified target.

Example 3:

Input: ./cross_compiler_generator --target invalid-target
Output:
error: Invalid target architecture: invalid-target

Explanation: The program detected an invalid target and printed an error message to standard error, exiting with a non-zero exit code.

Constraints

• Supported Targets: The program must support at least the following target architectures: x86_64-unknown-linux-gnu, arm-unknown-linux-musl, aarch64-unknown-linux-gnu, i686-unknown-linux-gnu. You can extend this list if you wish.
• Input Format: The target architecture must be provided as a command-line argument using the --target flag.
• Output Format: The output must be a valid config.toml file.
• Performance: The program should execute quickly, as it only generates a small configuration file. Performance is not a primary concern.
• Error Handling: The program must handle invalid input and file writing errors gracefully.

Notes

• You can use the clap crate for command-line argument parsing.
• You can use the toml crate for generating TOML files.
• The linker = "lld" setting is a reasonable default for many targets. You can modify this if needed.
• Focus on correctness and clarity of code. Error handling is important.
• Consider using a match statement or a HashMap to efficiently check for valid target architectures.
• The goal is to create a functional tool, not a highly optimized one.