2a4e06bcb3
This commit reworks how Sema handles arithmetic on comptime-known values, fixing many bugs in the process. The general pattern is that arithmetic on comptime-known values is now handled by the new namespace `Sema.arith`. Functions handling comptime arithmetic no longer live on `Value`; this is because some of them can emit compile errors, so some *can't* go on `Value`. Only semantic analysis should really be doing arithmetic on `Value`s anyway, so it makes sense for it to integrate more tightly with `Sema`. This commit also implements more coherent rules surrounding how `undefined` interacts with comptime and mixed-comptime-runtime arithmetic. The rules are as follows. * If an operation cannot trigger Illegal Behavior, and any operand is `undefined`, the result is `undefined`. This includes operations like `0 *| undef`, where the LHS logically *could* be used to determine a defined result. This is partly to simplify the language, but mostly to permit codegen backends to represent `undefined` values as completely invalid states. * If an operation *can* trigger Illegal Behvaior, and any operand is `undefined`, then Illegal Behavior results. This occurs even if the operand in question isn't the one that "decides" illegal behavior; for instance, `undef / 1` is undefined. This is for the same reasons as described above. * An operation which would trigger Illegal Behavior, when evaluated at comptime, instead triggers a compile error. Additionally, if one operand is comptime-known undef, such that the other (runtime-known) operand isn't needed to determine that Illegal Behavior would occur, the compile error is triggered. * The only situation in which an operation with one comptime-known operand has a comptime-known result is if that operand is undefined, in which case the result is either undefined or a compile error per the above rules. This could potentially be loosened in future (for instance, `0 * rt` could be comptime-known 0 with a runtime assertion that `rt` is not undefined), but at least for now, defining it more conservatively simplifies the language and allows us to easily change this in future if desired. This commit fixes many bugs regarding the handling of `undefined`, particularly in vectors. Along with a collection of smaller tests, two very large test cases are added to check arithmetic on `undefined`. The operations which have been rewritten in this PR are: * `+`, `+%`, `+|`, `@addWithOverflow` * `-`, `-%`, `-|`, `@subWithOverflow` * `*`, `*%`, `*|`, `@mulWithOverflow` * `/`, `@divFloor`, `@divTrunc`, `@divExact` * `%`, `@rem`, `@mod` Other arithmetic operations are currently unchanged. Resolves: #22743 Resolves: #22745 Resolves: #22748 Resolves: #22749 Resolves: #22914
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.