Compilation and execution flow in Rust - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the first step in Rust's compilation process?

The first step is parsing, where the Rust compiler reads the source code and checks its syntax to create a structured representation called an Abstract Syntax Tree (AST).

beginner

What does the Rust compiler do after parsing the source code?

After parsing, the compiler performs semantic analysis, which checks for meaning and correctness, like type checking and borrow checking to ensure safe memory use.

intermediate

What is the role of the LLVM backend in Rust's compilation?

LLVM backend takes the checked code and generates optimized machine code that the computer's processor can run directly.

beginner

What happens during the linking stage in Rust compilation?

The linker combines all compiled code and external libraries into a single executable file that can be run on your computer.

beginner

Describe the execution flow of a Rust program after compilation.

When you run the executable, the operating system loads it into memory, then the CPU starts executing instructions from the program's entry point (usually the main function), following the program's logic step-by-step.

What does the Rust compiler produce after the linking stage?

A Source code

B Bytecode

C Abstract Syntax Tree

D An executable file

After linking, the compiler produces an executable file that can be run on your computer.

Which component in Rust compilation checks for type errors and memory safety?

A Parser

B Semantic analyzer

C Linker

D LLVM backend

The semantic analyzer performs type checking and borrow checking to ensure memory safety.

What is the role of LLVM in Rust's compilation?

A Generating optimized machine code

B Linking libraries

C Parsing source code

D Running the program

LLVM generates optimized machine code from the checked Rust code.

When you run a Rust program, where does execution start?

A During parsing

B In the linker

C At the main function

D In the LLVM backend

Execution starts at the program's entry point, usually the main function.

Which step ensures all parts of a Rust program and libraries are combined into one file?

A Linking

B Semantic analysis

C Execution

D Parsing

Linking combines all compiled code and libraries into a single executable.

Explain the main stages of Rust's compilation process from source code to executable.

Think about how the code is read, checked, converted, and combined.

Describe what happens when you run a Rust program after compilation.

Focus on how the computer starts and follows the program instructions.

Practice

1. What is the first step when running a Rust program?

easy

A. Directly run the Rust source file without compiling

B. Compile the code using rustc to create an executable

C. Write the output to a file before compiling

D. Use an interpreter to execute the Rust code line by line

Solution

1. Step 1: Understand Rust's execution model

   Rust is a compiled language, so the source code must be compiled first.

2. Step 2: Identify the compilation tool

   The rustc compiler converts Rust code into an executable file.

3. Final Answer:

   Compile the code using rustc to create an executable -> Option B

4. Quick Check:

   Rust code is compiled first [OK]

Hint: Rust code must be compiled before running [OK]

Common Mistakes:

• Thinking Rust runs like a script without compiling
• Confusing Rust with interpreted languages
• Trying to run source code directly

2. Which command correctly compiles a Rust file named main.rs?

easy

A. run rustc main.rs

B. compile main.rs

C. rustc main.rs

D. cargo run main.rs

Solution

1. Step 1: Recall Rust compilation command

   The Rust compiler command is rustc followed by the filename.

2. Step 2: Check each option

   rustc main.rs matches the correct syntax: rustc main.rs.

3. Final Answer:

   rustc main.rs -> Option C

4. Quick Check:

   Use rustc filename.rs to compile [OK]

Hint: Use 'rustc' followed by filename to compile [OK]

Common Mistakes:

• Adding extra words like 'run' before rustc
• Using 'compile' instead of 'rustc'
• Confusing cargo commands with rustc

3. What will be the output when running this Rust program?

fn main() {
    println!("Hello, Rust!");
}

medium

A. Hello, Rust!

B. println!("Hello, Rust!");

C. Error: missing semicolon

D. No output

Solution

1. Step 1: Understand the println! macro

   This macro prints the string inside quotes to the console with a newline.

2. Step 2: Check the code correctness

   The code is syntactically correct and will print the message.

3. Final Answer:

   Hello, Rust! -> Option A

4. Quick Check:

   println! outputs the string [OK]

Hint: println! prints text to console with newline [OK]

Common Mistakes:

• Thinking println! prints the code itself
• Expecting no output without return statement
• Confusing macro syntax with function

4. Identify the error in this Rust code snippet:

fn main() {
    println!("Hello, world!")
}

medium

A. Missing closing parenthesis for println! macro

B. No error, code runs fine

C. Incorrect function name

D. Missing semicolon after println! macro

Solution

1. Step 1: Check statement termination syntax

   Rust requires semicolons to terminate expression statements like println! macro calls.

2. Step 2: Locate the missing semicolon

   The println! call is missing the terminating semicolon before the closing brace.

3. Final Answer:

   Missing semicolon after println! macro -> Option D

4. Quick Check:

   Expression statements require semicolon [OK]

Hint: Rust expression statements require a trailing semicolon [OK]

Common Mistakes:

• Thinking it's a parenthesis mismatch
• Confusing macros with block expressions
• Believing no semicolon needed before closing brace

5. You have two Rust files: lib.rs and main.rs. You want to compile main.rs which uses functions from lib.rs. What is the correct compilation and execution flow?

hard

A. Compile lib.rs into a library, then compile main.rs linking the library, then run the executable

B. Run main.rs directly without compiling lib.rs

C. Compile only main.rs, Rust automatically compiles lib.rs

D. Combine both files manually into one file before compiling

Solution

1. Step 1: Understand Rust's multi-file compilation

   The rustc compiler automatically handles referenced modules like lib.rs when compiling main.rs.

2. Step 2: Single command suffices

   With mod lib; in main.rs, rustc main.rs compiles both files and produces the executable.

3. Final Answer:

   Compile lib.rs into a library, then compile main.rs linking the library, then run the executable -> Option A

4. Quick Check:

   rustc main.rs compiles dependencies automatically [OK]

Hint: rustc compiles referenced modules automatically [OK]

Common Mistakes:

• Trying to run source files without compiling dependencies
• Assuming Rust compiles dependencies automatically at runtime
• Manually merging files instead of compiling separately