+++ title = "14. C Interoperability" weight = 14 +++

14. C Interoperability {#14-c-interoperability}

Zen C offers two ways to interact with C code: Trusted Imports (Convenient) and Explicit FFI (Safe/Precise).

Method 1: Trusted Imports (Convenient)

You can import a C header directly using the import keyword with the .h extension. This treats the header as a module and assumes all symbols accessed through it exist.

//> link: -lm
import "math.h" as c_math;

fn main() {
    // Compiler trusts correctness; emits 'cos(...)' directly
    let x = c_math::cos(3.14159);
}

Pros: Zero boilerplate. Access everything in the header immediately. Cons: No type safety from Zen C (errors caught by C compiler later).

Method 2: Explicit FFI (Safe)

For strict type checking or when you don't want to include the text of a header, use extern fn.

include <stdio.h> // Emits #include <stdio.h> in generated C

// Define strict signature
extern fn printf(fmt: char*, ...) -> c_int;

fn main() {
    printf("Hello FFI: %d\n", 42); // Type checked by Zen C
}

Pros: Zen C ensures types match. Cons: Requires manual declaration of functions.

import vs include

• import "file.h": Registers the header as a named module. Enables implicit access to symbols (for example, file::function()).
• include <file.h>: Purely emits #include <file.h> in the generated C code. Does not introduce any symbols to the Zen C compiler; you must use extern fn to access them.

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Standard Library

Zen C includes a standard library (std) covering essential functionality.

Browse the Standard Library Documentation

Key Modules

Click to see all Standard Library modules

Module	Description	Docs
std/bigfloat.zc	Arbitrary-precision floating-point arithmetic.	Docs
std/bigint.zc	Arbitrary-precision integer BigInt.	Docs
std/bits.zc	Low-level bitwise operations (rotl, rotr).	Docs
std/complex.zc	Complex Number Arithmetic Complex.	Docs
std/vec.zc	Growable dynamic array Vec<T>.	Docs
std/string.zc	Heap-allocated String type with UTF-8 support.	Docs
std/queue.zc	FIFO queue (Ring Buffer).	Docs
std/map.zc	Generic Hash Map Map<V>.	Docs
std/fs.zc	File system operations.	Docs
std/io.zc	Standard Input/Output (print/println).	Docs
std/option.zc	Optional values (Some/None).	Docs
std/result.zc	Error handling (Ok/Err).	Docs
std/path.zc	Cross-platform path manipulation.	Docs
std/env.zc	Process environment variables.	Docs
std/net/	TCP, UDP, HTTP, DNS, URL.	Docs
std/thread.zc	Threads and Synchronization.	Docs
std/time.zc	Time measurement and sleep.	Docs
std/json.zc	JSON parsing and serialization.	Docs
std/stack.zc	LIFO Stack Stack<T>.	Docs
std/set.zc	Generic Hash Set Set<T>.	Docs
std/process.zc	Process execution and management.	Docs
std/regex.zc	Regular Expressions (TRE based).	Docs
std/simd.zc	Native SIMD vector types.	Docs