Error Handling in Go vs.Zig

Aug 2 2025 golang 10 minutes read (About 1541 words)

Error Handling Redefined: Go and Zig’s ‘Errors as Values’ Philosophy

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Note: The core content was generated by an LLM, with human fact-checking and structural refinement.

In the realm of modern programming languages, particularly in systems programming, effective error handling is crucial. Go and Zig, two languages gaining significant attention, share a fundamental philosophy when it comes to managing errors: “Errors are values”. This shared principle dictates that errors are not “second-class citizens” like exceptions, but rather ordinary values that can be passed, checked, and even programmed. Both languages also emphasize a design philosophy of simplicity and “no hidden control flow,” aiming to make error propagation and handling explicit. However, despite this shared foundation, their implementations diverge significantly, leading to distinct approaches with their own trade-offs.

Go Error Handling

Go’s error handling mechanism is widely recognized for its straightforwardness. At its core, an error in Go is simply any type that implements the built-in error interface. This interface defines a single method: Error() string. This simple yet powerful convention allows developers to create custom error types that can hold various data and provide rich contextual information. For instance, a file operation might return an os.PathError, which includes fields like the operation (Op), the file path (Path), and the underlying system error. The standard errors package further enhances this by providing utilities like errors.Is to check if an error matches a specific target, and errors.As to check for and extract a specific error type from a chain.

Functions in Go typically indicate a possible error by returning multiple values, with the error value being the last one (e.g., func Open(name string) (*File, error)). Callers are then expected to explicitly check for a nil error value using the iconic if err != nil construct.

// Go Function returning an error
func Open(name string) (*File, error)

// Checking for nil error in Go
f, err := os.Open("main.zig")
if err != nil {
    // process the error
}

// One-liner for error checking
if err := f.Close(); err != nil {
    log.Fatal(err)
}

// Custom error type in Go
type errorString struct {
    s string
}
func (e *errorString) Error() string {
    return e.s
}
func New(text string) error {
    return &errorString{text}
}

// Checking error type with errors.Is
if errors.Is(err, fs.ErrNotExist) {
    // process error
}

While this explicit checking makes the control flow clear and ensures errors are not easily ignored, it can also lead to verbose code, with if err != nil blocks potentially making up a significant portion of a codebase. Critics sometimes refer to this as “if err bullshit that doesn’t do anything meaningful half the time”. However, Go’s philosophy emphasizes that “errors are values,” meaning they can be programmed. This allows for patterns to abstract away repetitive checks, such as the bufio.Scanner‘s Scan() method, which returns a boolean and reports the error separately via an Err() method at the end of the scan. Another example is the errWriter pattern, which records the first error encountered and turns subsequent writes into no-ops until the error is checked. This approach simplifies the code by centralizing error checks.

Zig Error Handling

Zig, a newer language, also treats errors as values, but implements this through a specialized enum that can be created implicitly. Errors are defined using error sets, which are like enums specifically designed for error values. Functions that can fail use error unions in their return types, indicated by an exclamation mark (!T or error{…}!T), signifying that the function can return either a value of type T or an error from its associated error set.

A key difference from Go is that the Zig compiler forcefully requires all potential errors to be handled; you cannot simply ignore a return error like you can with Go’s blank identifier _. This compile-time checking contributes to the language’s reliability.

Zig provides powerful syntactic sugar for handling errors:

try keyword: This is a concise mechanism for propagating errors up the call stack. A single try statement in Zig can replace three or four lines of if err != nil { return err } in Go.
catch keyword: Used to intercept and handle errors instead of propagating them.
- It can be combined with a code block (catch |err| { … }) to execute custom error handling logic, such as logging.
- It can provide a fallback return value (catch fallbackValue) when an error occurs, assigning a default successful value.
- It can be used with named blocks for more complex error processing before returning a fallback.
if-else-switch construct: This allows for precise handling of errors by branching based on specific error types within an else block.
catch unreachable: This mechanism is used in situations where errors are genuinely not expected (e.g., in tests, build scripts, or quick utilities). If an error does occur with catch unreachable, the program will panic.

// Zig Function returning an error union (!usize)
fn get_args_count(allocator: std.mem.Allocator) !usize {
    // Propagating an error using 'try'
    const args = try std.process.argsAlloc(allocator);
    if (args.len < 1) {
        return error.EmptyArgs;
    }
    return args.len;
}

pub fn main() void {
    // Catching an error with a block
    const args_count = get_args_count(allocator) catch |err| {
        // do some stuff, maybe log an error
        std.debug.print("invalid input: {}\n", .{err});
        return;
    };

    // Catching an error with a fallback value
    const args_count_fallback = get_args_count(allocator) catch 0;

    // Handling errors with if-else-switch
    if (get_args_count(allocator)) |args_count_val| {
        std.debug.print("got {d} args\n", .{args_count_val});
    } else |err| switch (err) {
        error.EmptyArgs => {
            std.debug.print("invalid input: no args\n", .{});
        },
        else => {
            std.debug.print("unexpected error: {}\n", .{err});
        },
    }

    // Using 'catch unreachable'
    const args_count_unreachable = get_args_count(allocator) catch unreachable;
    std.debug.print("got {d} args\n", .{args_count_unreachable});
}

// Defining an error set in Zig
const FileError = error { NotFound, PermissionDenied, InvalidPath, };

While Zig errors are essentially enum values and do not inherently carry rich contextual information or behavior within the enum itself, they do retain a debugging trace that is accessible at runtime via errorReturnTrace. Crucially, this error trace comes with zero runtime overhead when not explicitly used.

Comparison Trade-offs

Both Go and Zig successfully uphold the “errors are values” philosophy, avoiding the implicit control flow associated with exceptions. However, their distinct implementations reflect different design trade-offs:

Go’s approach is more direct and “clumsy” due to its verbosity, but it excels in allowing rich contextual errors through its interface-based system. This enables deep “programming with errors” by defining custom types that carry detailed information. The explicit if err != nil checks make every potential failure point clear.
Zig, on the other hand, offers a more concise, feature-rich, and powerful approach through its syntax sugar (try, catch) and compiler-enforced handling. This significantly reduces boilerplate code for error propagation. However, a notable trade-off is that Zig’s enum-based errors inherently lack the rich contextual information that Go’s interfaces can provide. While alternatives like tagged unions exist for adding context, it’s not as idiomatic as Go’s interface system.

In essence, Go prioritizes flexibility and extensive error information, which can lead to more repetitive code, while Zig prioritizes conciseness and compile-time guarantees, potentially sacrificing some inherent error context. Both approaches have their merits, reflecting different priorities in language design.

Resources:

“Comparing error handling in Zig and Go | by Alex Pliutau - ITNEXT”
“Error Handling in Zig: A Fresh Approach to Reliability - DEV Community”
“Error handling in Zig vs Go : r/programming - Reddit”
“Errors are values - The Go Programming Language”

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中文文章: https://programmerscareer.com/zh-cn/go-zig-error/
Author: Medium,LinkedIn,Twitter
Note: Originally written at https://programmerscareer.com/go-zig-error/ at 2025-08-02 21:58.
Copyright: BY-NC-ND 3.0

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Error Handling in Go vs.Zig

Go Error Handling

Zig Error Handling

Comparison Trade-offs

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