3afda4322c
This commit separates semantic analysis of the annotated type vs value
of a global declaration, therefore allowing recursive and mutually
recursive values to be declared.
Every `Nav` which undergoes analysis now has *two* corresponding
`AnalUnit`s: `.{ .nav_val = n }` and `.{ .nav_ty = n }`. The `nav_val`
unit is responsible for *fully resolving* the `Nav`: determining its
value, linksection, addrspace, etc. The `nav_ty` unit, on the other
hand, resolves only the information necessary to construct a *pointer*
to the `Nav`: its type, addrspace, etc. (It does also analyze its
linksection, but that could be moved to `nav_val` I think; it doesn't
make any difference).
Analyzing a `nav_ty` for a declaration with no type annotation will just
mark a dependency on the `nav_val`, analyze it, and finish. Conversely,
analyzing a `nav_val` for a declaration *with* a type annotation will
first mark a dependency on the `nav_ty` and analyze it, using this as
the result type when evaluating the value body.
The `nav_val` and `nav_ty` units always have references to one another:
so, if a `Nav`'s type is referenced, its value implicitly is too, and
vice versa. However, these dependencies are trivial, so, to save memory,
are only known implicitly by logic in `resolveReferences`.
In general, analyzing ZIR `decl_val` will only analyze `nav_ty` of the
corresponding `Nav`. There are two exceptions to this. If the
declaration is an `extern` declaration, then we immediately ensure the
`Nav` value is resolved (which doesn't actually require any more
analysis, since such a declaration has no value body anyway).
Additionally, if the resolved type has type tag `.@"fn"`, we again
immediately resolve the `Nav` value. The latter restriction is in place
for two reasons:
* Functions are special, in that their externs are allowed to trivially
alias; i.e. with a declaration `extern fn foo(...)`, you can write
`const bar = foo;`. This is not allowed for non-function externs, and
it means that function types are the only place where it is possible
for a declaration `Nav` to have a `.@"extern"` value without actually
being declared `extern`. We need to identify this situation
immediately so that the `decl_ref` can create a pointer to the *real*
extern `Nav`, not this alias.
* In certain situations, such as taking a pointer to a `Nav`, Sema needs
to queue analysis of a runtime function if the value is a function. To
do this, the function value needs to be known, so we need to resolve
the value immediately upon `&foo` where `foo` is a function.
This restriction is simple to codify into the eventual language
specification, and doesn't limit the utility of this feature in
practice.
A consequence of this commit is that codegen and linking logic needs to
be more careful when looking at `Nav`s. In general:
* When `updateNav` or `updateFunc` is called, it is safe to assume that
the `Nav` being updated (the owner `Nav` for `updateFunc`) is fully
resolved.
* Any `Nav` whose value is/will be an `@"extern"` or a function is fully
resolved; see `Nav.getExtern` for a helper for a common case here.
* Any other `Nav` may only have its type resolved.
This didn't seem to be too tricky to satisfy in any of the existing
codegen/linker backends.
Resolves: #131
A general-purpose programming language and toolchain for maintaining robust, optimal, and reusable software.
Documentation
If you are looking at this README file in a source tree, please refer to the Release Notes, Language Reference, or Standard Library Documentation corresponding to the version of Zig that you are using by following the appropriate link on the download page.
Otherwise, you're looking at a release of Zig, so you can find the language
reference at doc/langref.html, and the standard library documentation by
running zig std, which will open a browser tab.
Installation
A Zig installation is composed of two things:
- The Zig executable
- The lib/ directory
At runtime, the executable searches up the file system for the lib/ directory, relative to itself:
- lib/
- lib/zig/
- ../lib/
- ../lib/zig/
- (and so on)
In other words, you can unpack a release of Zig anywhere, and then begin
using it immediately. There is no need to install it globally, although this
mechanism supports that use case too (i.e. /usr/bin/zig and /usr/lib/zig/).
Building from Source
Ensure you have the required dependencies:
- CMake >= 3.15
- System C/C++ Toolchain
- LLVM, Clang, LLD development libraries == 19.x
Then it is the standard CMake build process:
mkdir build
cd build
cmake ..
make install
For more options, tips, and troubleshooting, please see the Building Zig From Source page on the wiki.
Building from Source without LLVM
In this case, the only system dependency is a C compiler.
cc -o bootstrap bootstrap.c
./bootstrap
This produces a zig2 executable in the current working directory. This is a
"stage2" build of the compiler,
without LLVM extensions, and is
therefore lacking these features:
- Release mode optimizations
- aarch64 machine code backend
- @cImport
- zig translate-c
- Ability to compile assembly files
- Some ELF linking features
- Most COFF/PE linking features
- Some WebAssembly linking features
- Ability to create import libs from def files
- Ability to create static archives from object files
- Ability to compile C, C++, Objective-C, and Objective-C++ files
However, a compiler built this way does provide a C backend, which may be useful for creating system packages of Zig projects using the system C toolchain. In this case, LLVM is not needed!
Furthermore, a compiler built this way provides an LLVM backend that produces bitcode files, which may be compiled into object files via a system Clang package. This can be used to produce system packages of Zig applications without the Zig package dependency on LLVM.
Contributing
Zig is Free and Open Source Software. We welcome bug reports and patches from everyone. However, keep in mind that Zig governance is BDFN (Benevolent Dictator For Now) which means that Andrew Kelley has final say on the design and implementation of everything.
One of the best ways you can contribute to Zig is to start using it for an open-source personal project.
This leads to discovering bugs and helps flesh out use cases, which lead to further design iterations of Zig. Importantly, each issue found this way comes with real world motivations, making it straightforward to explain the reasoning behind proposals and feature requests.
You will be taken much more seriously on the issue tracker if you have a personal project that uses Zig.
The issue label Contributor Friendly exists to help you find issues that are limited in scope and/or knowledge of Zig internals.
Please note that issues labeled Proposal but do not also have the Accepted label are still under consideration, and efforts to implement such a proposal have a high risk of being wasted. If you are interested in a proposal which is still under consideration, please express your interest in the issue tracker, providing extra insights and considerations that others have not yet expressed. The most highly regarded argument in such a discussion is a real world use case.
For more tips, please see the Contributing page on the wiki.
Community
The Zig community is decentralized. Anyone is free to start and maintain their own space for Zig users to gather. There is no concept of "official" or "unofficial". Each gathering place has its own moderators and rules. Users are encouraged to be aware of the social structures of the spaces they inhabit, and work purposefully to facilitate spaces that align with their values.
Please see the Community wiki page for a public listing of social spaces.