Go &amp; Rust

Rust Mocking: Using Traits as Test Seams

Mocking in Rust uses traits as test doubles. You program a mock's behavior—what calls to expect and what to return—to isolate the code under test. The mockall crate's #[automock] macro generates mocks from traits. The footgun is over-specifying behavior.

Go Fuzz Testing: Automated Bug Discovery

Go's fuzz testing automatically generates strange inputs to crash your code, finding bugs you'd never think to test. It's ideal for stress-testing parsers or security-sensitive functions.

Fuzz Testing in Rust with cargo-fuzz

Fuzz testing automatically finds bugs by feeding your code pseudo-random inputs. Use cargo-fuzz to stress-test parsers and APIs that handle untrusted data. The main footgun is assuming random bytes are enough; effective fuzzing needs structure-aware inputs.

Go Execution Tracer: Pinpointing Concurrency Bottlenecks

Go's Execution Tracer creates a visual timeline of your program, capturing goroutine state changes, syscalls, and GC events. It's essential for diagnosing subtle concurrency issues like lock contention. The main footgun is misusing annotations for work.

Rust `cfg`: Compile Code for Specific Targets

Rust's cfg attribute acts like a compile-time switch, including or excluding code based on the target platform or features. It's used for cross-platform support (e.g., Windows vs. Unix) or enabling optional dependencies.

Go Linker Flags: Injecting Data at Build Time

Go's -ldflags lets you inject data into your program at build time. This is perfect for embedding version numbers or git commit hashes into variables without hardcoding them. The main footgun is that the target variable must be a top-level string.

Go Reflection: Inspecting Types at Runtime

Go's reflect package lets your program inspect and manipulate variables of unknown types at runtime. This is the engine behind JSON marshaling and generic frameworks. Misuse leads to slow code and runtime panics; always prefer interfaces when possible.

Rust Declarative Macros (`macro_rules!`)

Think of macro_rules! as 'find and replace' for your code's structure. It matches patterns at compile time and expands them into boilerplate you don't want to write. It's used for helpers like vec![].

Rust's `unsafe` Keyword: Five Superpowers, Zero Guarantees

Rust's unsafe keyword lets you bypass certain compile-time memory safety guarantees for low-level tasks like OS interaction or FFI. The footgun is thinking it disables all safety; it only enables five specific 'superpowers,' making you responsible for…

Rust Raw Pointers: When References Aren't Enough

Raw pointers (*const T, *mut T) are Rust's C-style pointers, bypassing the borrow checker. They're used for FFI or building low-level abstractions. The footgun is assuming they're safe; they can be null or dangling, requiring unsafe to dereference.

Go's `unsafe` Package: Breaking the Rules for Performance

Go's unsafe package lets you bypass type safety, treating memory like C with raw pointers for performance gains. It's used for low-level optimizations and C interoperability. The footgun: its behavior isn't guaranteed across Go versions, making code fragile.

Cgo: The Bridge Between Go and C Code

Cgo is Go's bridge to the C world, letting you call C functions and use C types from your Go code. It's for leveraging existing C libraries or low-level OS APIs. The footgun: cgo calls have high overhead and break Go's simple cross-compilation.

Rust Procedural Macros: Code That Writes Code

Procedural macros are compile-time functions that write Rust code for you. They power common patterns like Serde's #[derive(Serialize)]. The main footgun is hygiene: generated code can clash with local variables, so authors must use absolute paths to be…

Rust Const Generics: Parameterize by Value, Not Just Type

Const generics let Rust types be parameterized by values, not just other types. This allows writing code generic over array sizes, like Matrix<T, const N: usize>, ensuring dimensions are checked at compile time.

Rust's Pin: Fixing a Value's Memory Address

Pin<P> tells the Rust compiler a value must not move from its memory location. Think of it as nailing an object to a specific spot on the memory shelf. This is crucial for self-referential types, like those in async runtimes.

Go Assembly: A Semi-Abstract Instruction Set

Go's assembler isn't a direct mapping to machine code; it's a semi-abstract instruction set. A MOV might become a clear or load. This is what you see with go tool compile -S. The footgun is assuming your assembly maps 1:1 to the final machine code.

Rust's `extern` Block: Talking to Other Languages

An extern block is Rust's contract for calling code from other languages, like C. You declare external functions and statics, promising they exist. Use it for FFI to call system libraries, but know all calls are unsafe as Rust can't verify them.

Rust's `libc` Crate: Speaking the OS's Language

The libc crate is Rust's dictionary for C types, letting you talk to the OS. Use it for system calls or linking C libraries, like when building low-level network tools.

Rust: Bridging C Strings with CStr and CString

CString and CStr are Rust's safe wrappers for C's nul-terminated strings. CString builds a C-compatible string to pass *out* of Rust; CStr interprets one coming *in*. Use them for any FFI calls.