Memory is not a guess.
A capacity-first memory model layer on top of the Zig compiler.
Every buffer is caller-owned. Every container is bounded. Every allocation is visible.
// zig — allocator is a runtime parameter, capacity is implicit
var list = std.ArrayList(u8).init(allocator);
try list.appendSlice(data); // might realloc 1x, 2x, 4x…
// sig — you provide the buffer, capacity is the type
var buf: [4096]u8 = undefined;
const result = try sig.fmt.formatInto(&buf, "{s}: {d}", .{ name, count });// bounded container — capacity is comptime-known
var vec = sig.containers.BoundedVec(u32, 1024){};
try vec.push(10);
try vec.push(20); // returns CapacityExceeded if fullThe .sig file extension enables strict mode. Same syntax as .zig, same parser, same compiler — but allocator usage is a compile error.
src/core.sig:42:5: error: direct allocation in 'init' (.sig file: strict mode enforced)
| File | allocator.alloc(...) |
Behavior |
|---|---|---|
foo.zig |
Allowed | Warning (or error with --sig-mode=strict) |
foo.sig |
Not allowed | Compile error, always |
.sig and .zig files interoperate via @import. You can adopt strict mode one file at a time.
Four explicit errors instead of silent reallocation:
| Error | Meaning |
|---|---|
BufferTooSmall |
Output exceeds the caller-provided buffer |
CapacityExceeded |
Bounded container is full |
DepthExceeded |
Recursive operation hit depth limit |
QuotaExceeded |
Resource usage limit reached |
Standard Zig error unions. Handle with try, catch, or orelse.
| Pattern | In .sig files |
|---|---|
var buf: [1024]u8 = undefined; |
✅ |
fn read(buf: []u8) ![]u8 |
✅ |
BoundedVec(u8, 256) |
✅ |
FixedPool(Node, 64) |
✅ |
allocator.alloc(u8, n) |
❌ compile error |
fn init(alloc: Allocator) |
❌ compile error |
list.ensureTotalCapacity(n) |
❌ compile error |
In .zig files, the ❌ patterns compile normally (with optional warnings).
Sig is not a fork. It's a Spoon 🥄
A Spoon is a close derivative that stays continuously synchronized with its upstream. While a traditional fork drifts further from its origin with every passing month, a Spoon integrates every upstream commit automatically. Sig tracks the upstream Zig compiler and standard library through sig-sync — every commit in ziglang/zig flows into Sig within minutes.
| Traditional Fork | Spoon (Sig) | |
|---|---|---|
| Upstream tracking | Manual, periodic | Continuous, automatic |
| Divergence over time | Grows unbounded | Near zero |
| Merge conflicts | Accumulate silently | Resolved immediately |
| Upstream compatibility | Degrades | Always maintained |
| Latest upstream commit | ce198b7c |
| Last sync | 2026-04-28 |
| Upstream | codeberg.org/ziglang/zig |
| Base version | zig 0.17.0-dev · LLVM 22.1.3 |
| Sync frequency | Every commit (< 1 min latency) |
The sync status above is updated automatically after each successful integration. See the sig-sync workflow for live run history.
Download a binary from releases, or build from source:
git clone https://github.com/SB0LTD/sig.git
cd sig && sig buildDrop-in replacement for zig. All existing .zig code works unchanged.
$ sig version
sig 0.1.2 (zig 0.17.0-dev)
Sig follows its own semver while tracking the upstream Zig version it's built on. Release tags encode both: sig-0.1.2+zig0.17.0.<sha>.
All sig stdlib APIs must follow the capacity-first model — no Allocator parameters in public interfaces. See CONTRIBUTING.md for details.
Same as upstream Zig. See LICENSE.