C3 0.8.2 A modest improvement

C3 0.8.2 is out. This release brings a batch of language ergonomics improvements — most notably reusable target templates for libraries and generic constdef — along with new reflection capabilities and a round of bug fixes.

Compared to 0.8.1, this is a rather modest release, but anyway, here's what's new:

Language changes & improvements¶

Reusable target configurations for libraries¶

Libraries can now expose a templates map in their manifest, and projects can pull one into a target with template: "library/template". Template properties load first and target-local settings override them, so libraries can ship sensible, shareable build configurations instead of asking every user to copy-paste setup.

Reflection for generics¶

Foo::is_generic(...), Foo::generic_qname, and Foo::generic_args finally lets you inspect generic instantiations.

alias Foo = List{int};

fn void main()
{
    typeid t = List{String}::generic_args[0]; //String::typeid
    String name = Foo::generic_qname; // "std::collections::list::List"
    bool x = Foo::is_generic(List); // true
    bool y = int::is_generic(List); // false
}

Bitstruct properties¶

Bitstruct members gain bitoffset and bitsize properties:

bitstruct Foo : uint
{
   uint a : 0..1;
   bool b : 6;
   bool c : 10;
   int d : 14..20;
}

fn void main()
{
    int a = $reflect(Foo.a).bitsize; // 2
    int b = $reflect(Foo.d).bitoffset; // 14
    int c = $reflect(Foo.c).bitoffset; // 10
}

New @param options: own, init and drop¶

It's now possible to annotate more than in/inout/out on parameters:

1. own signifies that the function will in some way retain the variable beyond the scope of the function.
2. drop means that the pointer and the data pointed to will be invalid when the function returns.
3. init means that the data in pointed to will be initialized by the function.

This can be used by the compiler for static analysis and also documents the function or macro.

<* 
 @param [own] f
*> 
fn void foo(Foo* f)
{
    some_global.foo = f;
}

Asm stack alignment¶

Before 0.8.2, all asm blocks would be stack aligned, which didn't match C behaviour. This is now fixed. Stack alignment is now opt-in by using @align:

asm // Unaligned
{
  syscall;
}

asm @align // Stack aligned
{
  syscall;
}

Windows improvements¶

The Windows subsystem can now be set directly. Windows can still use @winmain to implicitly set the Window subsystem, but all subsystems are now available, allowing for things like EFI applications.

Standard library¶

• Atomic.compare_exchange added.
• array::contains_slice and array::index_of_slice for substring-style searches over arrays.
• log::register_dynamic_category, for libraries to define their own logging categories dynamically.
• String.index_of and rindex_of now accept finding empty strings.

Fixes¶

Stdlib fixes¶

• Denormal (subnormal) results are now handled correctly by String.to_double() — very small magnitudes near the floating-point floor previously came out wrong.
• A float literal with an uppercase F suffix was incorrectly typed as a double instead of a float.
• JSON serialization now correctly handles Unicode and \v (#3353).
• IPv6 parsing: "a::b:c:d:e:f:0" is now accepted as valid.
• A regression in BackedArenaAllocator when destroying it could cause a crash.
• Fixed macOS regression which was breaking stack traces.

Compiler fixes¶

• $stringify would sometimes wrap output in extra parentheses.
• constdef vector with an alias was incorrectly lowered
• The compiler asserted when concatenating a struct to an untypedlist
• untypedlist was not detected as invalid as an enum associated-value type or as a pointer

Thank yous¶

Again, this release wouldn't have been possible without the C3 community. I'd like to extend a deep thank you to all who have contributed, both through filed issues, PRs and just plain discussions.

PR contributors for this release¶

Stdlib: AtomicSynth, Book-reader, GuineaPigUuhh and Manu Linares

Compiler & toolchain: Book-reader, Johannes Müller, Manu Linares, Osama Badeeb, rickyadastra and Rodrigo Camacho

CI/Infrastructure: Hade and Manu Linares

Change Log¶

Want To Dive Into C3?¶

Check out the documentation or download it and try it out.

Have questions? Come and chat with us on Discord.