A few of the most essential libc functions needed when working with C code in Zig.

Much of the code is taken from ziglibc.

ZeptoLibC provides, among others:

• malloc(), calloc(), realloc(), free()
• printf(), fprintf(), snprintf()
• strncmp(), strchr(), strncpy()
• abs(), fabs(), sin(), cos(), sqrt(), pow(), floor(), ceil()
• memset(), memmove()

ZeptoLibC is not intended to implement the full C library and does the bare minimum to support I/O operations (just printf()). The aim is to allow simple porting of existing C code to freestanding/baremetal environments such as WASM and embedded systems.

All ZeptoLibC functions start with the prefix zepto_, eg. zepto_malloc() so as to not clash with any existing C functions. The file zeptolibc.h provides #defines for mapping malloc() -> zepto_malloc().

For a complete example, see https://github.com/ringtailsoftware/zeptolibc-example

First we add the library as a dependency in our build.zig.zon file.

zig fetch --save git+https://github.com/ringtailsoftware/zeptolibc.git

And we add it to build.zig file.

const zeptolibc_dep = b.dependency("zeptolibc", .{
    .target = target,
    .optimize = optimize,
});
exe.root_module.addImport("zeptolibc", zeptolibc_dep.module("zeptolibc"));
exe.addIncludePath(zeptolibc_dep.path("src/"));

Add #include "zeptolibc.h" to your C code.

    #include "zeptolibc.h"
    void my_greeting(void) {
        printf("Hello world\n");
    }

Setup ZeptoLibC from Zig and call the C code.

zeptolibc.init() may be passed null for both write function and allocator. A null allocator will cause malloc() to always return NULL. A null write function will silently drop written data.

    const std = @import("std");
    const zeptolibc = @import("zeptolibc");
    const c = @cImport({
        @cInclude("greeting.c");
    });
    fn writeFn(data:[]const u8) void {
        _ = std.io.getStdOut().writer().write(data) catch 0;
    }
    pub fn main() !void {
        var gpa = std.heap.GeneralPurposeAllocator(.{}){};
        const allocator = gpa.allocator();
        // init zepto with a memory allocator and a write function (used for stdout and stderr)
        zeptolibc.init(allocator, writeFn);
        c.my_greeting();
    }