gccrs: Register lang items for alloc crate
gccrs: Registers stub language items to enable compilation of the alloc crate.
This patch registers several language items as stubs to enable the compilation of the ‘alloc’ crate in gccrs. Stubs are used for items like ‘oom’, ‘alloc_layout’, ‘box_free’, ‘drop_in_place’, ‘maybe_uninit’, async-related items, and generator support, as their full implementation requires more mature infrastructure within the compiler. New tests are added to verify the registration of these stub language items.
In Details
The gccrs compiler needs to register language items, which are special global symbols with specific semantics in the Rust ecosystem. This commit adds stub registrations for numerous lang items required by the 'alloc' crate, such as memory management (oom, box_free, drop_in_place), layout calculations (alloc_layout), and future language features (async, generators). These stubs allow the 'alloc' crate to be processed by the AST lowering phase, even though the full functionality isn't yet implemented in gccrs.
- lang items
- Special functions or statics in Rust that have a predefined meaning to the compiler, often used for fundamental operations like memory allocation, dropping values, or handling panics. They are essential for the core functionality of the language and its standard library.
- alloc crate
- A fundamental Rust crate that provides memory allocation primitives, such as
Box,Vec, andString. It relies on language items for its core operations. Compiling this crate is a significant step towards a functional Rust toolchain. - stub
- A placeholder implementation for a function or feature that is not yet fully developed. Stubs allow other parts of the system to compile and link even when a component is incomplete, often providing minimal or no-op functionality.
- AST lowering
- A phase in the compiler where the Abstract Syntax Tree (AST) is transformed into an intermediate representation (IR) that is closer to executable code. In gccrs, this involves converting Rust's high-level AST into a form that the compiler's backend can process.