Another month and another C3 0.5.x release (read the 0.5.4 announcement here), grab it here: As work on 0.6.0 is underway, 0.5.5 contains much fewer language updates, and instead mostly contains bug fixes.

In other news, the C3 site has gotten a face-lift: It's still a work in progress with more extensive guides planned.

For 0.5.5 the biggest feature is the new @link attribute. It works similar to #pragma comment(lib, ...) supported by MSVC and Clang.

module std::os::macos::cf @link(env::DARWIN, "CoreFoundation.framework");

// Use of any functions in this module section
// will implicitly link the CoreFoundation framework


While library dependencies still can be specified in project and library settings, this features allows fine grained dependency tracking, avoids superfluous linking. You link what you use, not more.

0.5.5 sees a lot of important fixes, such as the broken output directory setting for projects (and fixes the project template for the corresponding setting!)

The standard library has gotten new_aligned and alloc_aligned as new and alloc would not work correctly on over-aligned types, such as vectors wider than 16 bytes. In mem copy/clear/set functions now has a separate inline variant, which is important as inline requires a compile time length.

Previously aligned alloc using libc would have an extra overhead to support it, but now on POSIX and Windows native aligned allocations are used, avoiding this problem.

Here is the full change list:

Changes / improvements

  • Disallow multiple _ in a row in digits, e.g. 1__000.
  • Added @link attribute.
  • New 'linker' build option.
  • "linker" project setting updated, "system-linker" removed.


  • Struct/union members now correctly rejects members without storage size #1147.
  • math::pow will now correctly promote integer arguments.
  • Pointer difference would fail where alignment != size (structs etc) #1150
  • Fixed array calculation for npot2 vectors.
  • $$memcpy_inline and $$memset_inline fixed.
  • .$Type = ... and .$foo = ... now works #1156.
  • int.min incorrect behaviour #1154.
  • Bitstruct cast to other bitstruct by way of underlying type would fail #1159.
  • Bug in time.add_seconds #1162.
  • Remove initial './' in Win32 paths when running a binary.
  • 'output' directory for projects was incorrect in templates.
  • Regression: no stacktrace.
  • For MacOS, running with higher optimization would crash as initializers were removed.
  • compile-run and run now returns the proper return code.
  • Allow String constants -> ichar*, and allow integer pointers to explicitly convert between unsigned signed.
  • Bug in unaligned return value lowering for Aarch64.

Stdlib changes

  • Added new_aligned and alloc_aligned functions to prevent accidental under-alignment when allocating simd.
  • Fixes to realloc of aligned allocations
  • Use native Windows calls on aligned allocations on Windows.
  • mem::copy_inline, mem::clear_inline and mem::set_inline added.
  • mem::copy / clear / set no longer has an $inline attribute.
  • Native aligned libc malloc on Windows & POSIX.
  • Simplification of the allocator interface.
  • CoreFoundation only linked on MacOS when used.

0.5 has feature stability guarantees, so code written for 0.5.0-0.5.4 will work with 0.5.5.

If you want to read more about C3, check out the documentation: or download it and try it out: