C3 0.8.2 A modest improvement

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.

`[](https://c3-lang.org/blog/0%5F8%5F2%5Fa%5Fmodest%5Fimprovement/#%5F%5Fcodelineno-0-1)alias Foo = List{int}; [](https://c3-lang.org/blog/0%5F8%5F2%5Fa%5Fmodest%5Fimprovement/#%5F%5Fcodelineno-0-2) [](https://c3-lang.org/blog/0%5F8%5F2%5Fa%5Fmodest%5Fimprovement/#%5F%5Fcodelineno-0-3)fn void main() [](https://c3-lang.org/blog/0%5F8%5F2%5Fa%5Fmodest%5Fimprovement/#%5F%5Fcodelineno-0-4){ [](https://c3-lang.org/blog/0%5F8%5F2%5Fa%5Fmodest%5Fimprovement/#%5F%5Fcodelineno-0-5) typeid t = List{String}::generic_args[0]; //String::typeid [](https://c3-lang.org/blog/0%5F8%5F2%5Fa%5Fmodest%5Fimprovement/#%5F%5Fcodelineno-0-6) String name = Foo::generic_qname; // "std::collections::list::List" [](https://c3-lang.org/blog/0%5F8%5F2%5Fa%5Fmodest%5Fimprovement/#%5F%5Fcodelineno-0-7) bool x = Foo::is_generic(List); // true [](https://c3-lang.org/blog/0%5F8%5F2%5Fa%5Fmodest%5Fimprovement/#%5F%5Fcodelineno-0-8) bool y = int::is_generic(List); // false [](https://c3-lang.org/blog/0%5F8%5F2%5Fa%5Fmodest%5Fimprovement/#%5F%5Fcodelineno-0-9)} `

Bitstruct properties

Bitstruct members gain `bitoffset` and `bitsize` properties:

`[](https://c3-lang.org/blog/0%5F8%5F2%5Fa%5Fmodest%5Fimprovement/#%5F%5Fcodelineno-1-1)bitstruct Foo : uint [](https://c3-lang.org/blog/0%5F8%5F2%5Fa%5Fmodest%5Fimprovement/#%5F%5Fcodelineno-1-2){ [](https://c3-lang.org/blog/0%5F8%5F2%5Fa%5Fmodest%5Fimprovement/#%5F%5Fcodelineno-1-3) uint a : 0..1; [](https://c3-lang.org/blog/0%5F8%5F2%5Fa%5Fmodest%5Fimprovement/#%5F%5Fcodelineno-1-4) bool b : 6; [](https://c3-lang.org/blog/0%5F8%5F2%5Fa%5Fmodest%5Fimprovement/#%5F%5Fcodelineno-1-5) bool c : 10; [](https://c3-lang.org/blog/0%5F8%5F2%5Fa%5Fmodest%5Fimprovement/#%5F%5Fcodelineno-1-6) int d : 14..20; [](https://c3-lang.org/blog/0%5F8%5F2%5Fa%5Fmodest%5Fimprovement/#%5F%5Fcodelineno-1-7)} [](https://c3-lang.org/blog/0%5F8%5F2%5Fa%5Fmodest%5Fimprovement/#%5F%5Fcodelineno-1-8) [](https://c3-lang.org/blog/0%5F8%5F2%5Fa%5Fmodest%5Fimprovement/#%5F%5Fcodelineno-1-9)fn void main() [](https://c3-lang.org/blog/0%5F8%5F2%5Fa%5Fmodest%5Fimprovement/#%5F%5Fcodelineno-1-10){ [](https://c3-lang.org/blog/0%5F8%5F2%5Fa%5Fmodest%5Fimprovement/#%5F%5Fcodelineno-1-11) int a = $reflect(Foo.a).bitsize; // 2 [](https://c3-lang.org/blog/0%5F8%5F2%5Fa%5Fmodest%5Fimprovement/#%5F%5Fcodelineno-1-12) int b = $reflect(Foo.d).bitoffset; // 14 [](https://c3-lang.org/blog/0%5F8%5F2%5Fa%5Fmodest%5Fimprovement/#%5F%5Fcodelineno-1-13) int c = $reflect(Foo.c).bitoffset; // 10 [](https://c3-lang.org/blog/0%5F8%5F2%5Fa%5Fmodest%5Fimprovement/#%5F%5Fcodelineno-1-14)} `

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 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.

`[](https://c3-lang.org/blog/0%5F8%5F2%5Fa%5Fmodest%5Fimprovement/#%5F%5Fcodelineno-2-1)<* [](https://c3-lang.org/blog/0%5F8%5F2%5Fa%5Fmodest%5Fimprovement/#%5F%5Fcodelineno-2-2) @param [own] f [](https://c3-lang.org/blog/0%5F8%5F2%5Fa%5Fmodest%5Fimprovement/#%5F%5Fcodelineno-2-3)*> [](https://c3-lang.org/blog/0%5F8%5F2%5Fa%5Fmodest%5Fimprovement/#%5F%5Fcodelineno-2-4)fn void foo(Foo* f) [](https://c3-lang.org/blog/0%5F8%5F2%5Fa%5Fmodest%5Fimprovement/#%5F%5Fcodelineno-2-5){ [](https://c3-lang.org/blog/0%5F8%5F2%5Fa%5Fmodest%5Fimprovement/#%5F%5Fcodelineno-2-6) some_global.foo = f; [](https://c3-lang.org/blog/0%5F8%5F2%5Fa%5Fmodest%5Fimprovement/#%5F%5Fcodelineno-2-7)} `

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`:

`[](https://c3-lang.org/blog/0%5F8%5F2%5Fa%5Fmodest%5Fimprovement/#%5F%5Fcodelineno-3-1)asm // Unaligned [](https://c3-lang.org/blog/0%5F8%5F2%5Fa%5Fmodest%5Fimprovement/#%5F%5Fcodelineno-3-2){ [](https://c3-lang.org/blog/0%5F8%5F2%5Fa%5Fmodest%5Fimprovement/#%5F%5Fcodelineno-3-3) syscall; [](https://c3-lang.org/blog/0%5F8%5F2%5Fa%5Fmodest%5Fimprovement/#%5F%5Fcodelineno-3-4)} [](https://c3-lang.org/blog/0%5F8%5F2%5Fa%5Fmodest%5Fimprovement/#%5F%5Fcodelineno-3-5) [](https://c3-lang.org/blog/0%5F8%5F2%5Fa%5Fmodest%5Fimprovement/#%5F%5Fcodelineno-3-6)asm @align // Stack aligned [](https://c3-lang.org/blog/0%5F8%5F2%5Fa%5Fmodest%5Fimprovement/#%5F%5Fcodelineno-3-7){ [](https://c3-lang.org/blog/0%5F8%5F2%5Fa%5Fmodest%5Fimprovement/#%5F%5Fcodelineno-3-8) syscall; [](https://c3-lang.org/blog/0%5F8%5F2%5Fa%5Fmodest%5Fimprovement/#%5F%5Fcodelineno-3-9)} `

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

Click for full change log

Changes / improvements

• `@weak` now works with all declarations.
• Add `@align` for asm blocks to stack align them. Stack alignment is no longer default.
• Allow setting Windows subsystem directly.
• Add `bitoffset` and `bitsize` reflection properties to bitstruct members. #3219
• Improve error message on trying to cast char array to String. #3343
• Add `Foo::is_generic(...)`, `Foo::generic_qname` and `Foo::generic_args`. #2909 #3329
• Add `own`, `init` and `drop` parameter annotations.
• `constdef` can now be generic.
• Libraries can now expose reusable target configurations via a `templates` map in their manifest, which projects reference from a target using `template: "library/template"`. Properties from the template are loaded first and can be overridden by target-local settings.

Stdlib changes

• `Atomic.compare_exchange` added.
• Added `array::contains_slice` and `array::index_of_slice`.
• `String.index_of` and `rindex_of` will now accept finding empty strings.
• Add log::register\_dynamic\_category, for libraries that wish to define their own categories dynamically.

Fixes

• `$stringify` would sometimes include parens.
• Regression when destroying a BackedArenaAllocator in some cases #3332.
• `"a::b:c:d:e:f:0"` was not parsed as a valid ipv6 string.
• `constdef` vector with alias incorrectly lowered #3335.
• Compiler asserts on concatenating a struct to an untypedlist #3326.
• `untypedlist` was not detected as invalid in enum associated value type or as a pointer #3342.
• Regression using non-posix libc.
• Crash with an optional struct recursively defined with a function type. #3358
• Denormal results were not handled correctly by `String.to_double()`.
• A float literal with an uppercase 'F' suffix would be a `double` instead of a `float`.
• Json serialization would not correctly handle unicode and `\v`. #3353
• Semantic checking was incorrect in the case of `&a - &b` where one or both are optional and the result isn't assigned.
• Regression on MacOS, breaking stack trace.

Want To Dive Into C3?

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