Crate rustc_abi 

ABI handling for rustc

What is an “ABI”?

Literally, “application binary interface”, which means it is everything about how code interacts, at the machine level, with other code. This means it technically covers all of the following:

• object binary format for e.g. relocations or offset tables
• in-memory layout of types
• procedure calling conventions

When we discuss “ABI” in the context of rustc, we are probably discussing calling conventions. To describe those rustc_abi also covers type layout, as it must for values passed on the stack. Despite rustc_abi being about calling conventions, it is good to remember these usages exist. You will encounter all of them and more if you study target-specific codegen enough! Even in general conversation, when someone says “the Rust ABI is unstable”, it may allude to either or both of

• repr(Rust) types have a mostly-unspecified layout
• extern "Rust" fn(A) -> R has an unspecified calling convention

Crate Goal

ABI is a foundational concept, so the rustc_abi crate serves as an equally foundational crate. It cannot carry all details relevant to an ABI: those permeate code generation and linkage. Instead, rustc_abi is intended to provide the interface for reasoning about the binary interface. It should contain traits and types that other crates then use in their implementation. For example, a platform’s extern "C" fn calling convention will be implemented in rustc_target but rustc_abi contains the types for calculating layout and describing register-passing. This makes it easier to describe things in the same way across targets, codegen backends, and even other Rust compilers, such as rust-analyzer!

Re-exports

pub use callconv::Heterogeneous;

pub use callconv::HomogeneousAggregate;

pub use callconv::Reg;

pub use callconv::RegKind;

pub use canon_abi::ArmCall;

pub use canon_abi::CanonAbi;

pub use canon_abi::InterruptKind;

pub use canon_abi::X86Call;

pub use extern_abi::CVariadicStatus;

pub use extern_abi::ExternAbi;

pub use extern_abi::all_names;

pub use layout::FIRST_VARIANT;

pub use layout::FieldIdx;

pub use layout::LayoutCalculator;

pub use layout::LayoutCalculatorError;

pub use layout::VariantIdx;

pub use layout::Layout;

pub use layout::TyAbiInterface;

pub use layout::TyAndLayout;

pub use wrapping_range::WrappingRange;

pub(crate) use std::cmp::min; 🔒

pub(crate) use std::fmt; 🔒

pub(crate) use std::iter::Step; 🔒 Experimental

pub(crate) use NonZero; 🔒

pub(crate) use ParseIntError; 🔒

pub(crate) use Add; 🔒

pub(crate) use AddAssign; 🔒

pub(crate) use Mul; 🔒

pub(crate) use Sub; 🔒

pub(crate) use std::range::RangeInclusive; 🔒

pub(crate) use std::str::FromStr; 🔒

pub(crate) use bitflags::bitflags; 🔒

pub(crate) use rustc_data_structures::stable_hash::StableOrd; 🔒

pub(crate) use DiagArgValue; 🔒

pub(crate) use IntoDiagArg; 🔒

pub(crate) use Diag; 🔒

pub(crate) use DiagCtxtHandle; 🔒

pub(crate) use Diagnostic; 🔒

pub(crate) use Level; 🔒

pub(crate) use msg; 🔒

pub(crate) use rustc_hashes::Hash64; 🔒

pub(crate) use Idx; 🔒

pub(crate) use IndexSlice; 🔒

pub(crate) use IndexVec; 🔒

pub(crate) use Decodable_NoContext; 🔒

pub(crate) use Encodable_NoContext; 🔒

pub(crate) use StableHash; 🔒

pub(crate) use Symbol; 🔒

pub(crate) use sym; 🔒

Modules

callconv 🔒

canon_abi 🔒

extern_abi 🔒

layout 🔒

wrapping_range 🔒

Structs

AddressSpace

An identifier that specifies the address space that some operation should operate on. Special address spaces have an effect on code generation, depending on the target and the address spaces it implements.

Align

Alignment of a type in bytes (always a power of two).

BackendLaneCount

The number of lanes in a BackendRepr::SimdVector, 1..=MAX_SIMD_LANES.

LayoutData

Niche

NumScalableVectors

How many scalable vectors are in a BackendRepr::ScalableVector?

PointeeInfo

Encodes extra information we have about a pointer.

PointerSpec

How pointers are represented in a given address space

ReprFlags

ReprOptions

Represents the repr options provided by the user.

Size

Size of a type in bytes.

TargetDataLayout

Parsed Data layout for a target, which contains everything needed to compute layouts.

VariantLayout

The layout information for a variant.

Enums

AbiFromStrErr

AlignFromBytesError

BackendRepr

The way we represent values to the backend

Endian

Endianness of the target, which must match cfg(target-endian).

FieldsShape

Describes how the fields of a type are located in memory.

Float

Floating-point types.

Integer

Integers, also used for enum discriminants.

IntegerType

NicheOptimizations

Whether niche optimizations should be performed during layout calculation.

Numeric

Numeric primitives.

PointerKind

Primitive

Fundamental unit of memory access and layout.

ScalableElt

Scalar

Information about one scalar component of a Rust type.

StructKind

TagEncoding

TargetDataLayoutError

Variants

Describes the variants of a type.

Constants

MAX_SIMD_LANES

The maximum supported number of lanes in a SIMD vector.

Traits

HasDataLayout