Standard Library overview

The standard library lives in the std/ directory of the repository and is written entirely in Marrow itself (.mw files) — it’s a thin, explicit wrapper around C standard library functions via @extern, plus a handful of hand-rolled data structures (dynamic arrays, hash maps, an arena allocator, a growable string type).

Every file in std/ starts with @no_main, which is what marks them as libraries rather than standalone programs (see Modules & decorators).

Modules

File	What it provides
io.mw	Printing to stdout/stderr.
mem.mw	Raw allocation (malloc/realloc/free), memcpy/memset wrappers, and an arena allocator.
string.mw	C-string helpers (str_len, str_eq, character classification) and a growable String type.
vec.mw	Growable arrays: VecPtr (of rawptr) and VecI64 (of i64).
map.mw	LinearMap (linear-scan key/value store) and HashMap (DJB2 hash map with chaining).
fs.mw	File I/O: open/close/read/write, whole-file read into a String.
sys.mw	Process exit, shelling out to system(3), panic/assert.
std.mw	The umbrella module — @imports every file above, plus a VERSION constant.

Importing it

@import("std")

This resolves to std/std.mw (see the exact resolution rules on the Modules & decorators page) and transitively pulls in every module listed above. If you only need one module, you can import it directly instead, e.g.:

@import("mem.mw")   // just the allocator, no io/string/vec/map/fs/sys

Modules @import each other where they depend on one another (e.g. string.mw imports mem.mw for alloc/realloc; map.mw imports mem.mw, sys.mw, vec.mw and string.mw) — the deduplication rule described on the modules page means importing the same file from multiple places is always safe.

Design notes that apply across the whole standard library

• Naming convention: functions that are thin @extern bindings to a C library function are prefixed c_ (c_malloc, c_printf, c_fopen, …) and are not meant to be called directly from your code — call the Marrow-native wrapper next to them instead (alloc, print, file_open_read, …).
• No exceptions, no Result/Option types. Errors are signaled the C way: a null pointer (0), a negative/zero return code, or (for genuinely unrecoverable situations) panic() which prints a message to stderr and calls exit(1).
• Manual memory management throughout. Every _new function that allocates has a matching _free function; nothing here uses the arena allocator internally by default (it’s opt-in — the arena is a tool you reach for, see mem.mw).
• Growable containers (String, VecPtr, VecI64) all follow the same doubling-growth strategy: when full, capacity is doubled and the buffer is realloc’d.