Expand description

An interpreter for MIR used in CTFE and by miri


cast 🔒
intern 🔒

This module specifies the type based interner for constants.

intrinsics 🔒

Intrinsics and other functions that the miri engine executes without looking at their MIR. Intrinsics/functions supported here are shared by CTFE and miri.

machine 🔒

This module contains everything needed to instantiate an interpreter. This separation exists to ensure that no fancy miri features like interpreting common C functions leak into CTFE.

memory 🔒

The memory subsystem.

operand 🔒

Functions concerning immediate values and operands, and reading from operands. All high-level functions to read from memory work on operands as sources.

operator 🔒
place 🔒

Computations on places – field projections, going from mir::Place, and writing into a place. All high-level functions to write to memory work on places as destinations.

step 🔒

This module contains the InterpCx methods for executing a single step of the interpreter.

terminator 🔒
traits 🔒
util 🔒
validity 🔒

Check the validity invariant of a given value, and tell the user where in the value it got violated. In const context, this goes even further and tries to approximate const safety. That’s useful because it means other passes (e.g. promotion) can rely on consts to be const-safe.

visitor 🔒

Visitor for a run-time value with a given layout: Traverse enums, structs and other compound types until we arrive at the leaves, with custom handling for primitive types.



The information that makes up a memory access: offset and size.

A reference to some allocation that was already bounds-checked for the given region and had the on-access machine hooks run.

A reference to some allocation that was already bounds-checked for the given region and had the on-access machine hooks run.

This type represents an Allocation in the Miri/CTFE core engine.

Represents the result of const evaluation via the eval_to_allocation query.

Interned types generally have an Outer type and an Inner type, where Outer is a newtype around Interned<Inner>, and all the operations are done on Outer, because all occurrences are interned. E.g. Ty is an outer type and TyS is its inner type.

A stack frame.

What we store about a frame in an interpreter backtrace.

Uniquely identifies one of the following:

A bitmask where each bit refers to the byte with the same index. If the bit is true, the byte is initialized. If it is false the byte is uninitialized.

Packages the kind of error we got from the const code interpreter up with a Rust-level backtrace of where the error occurred. These should always be constructed by calling .into() on an InterpError. In rustc_mir::interpret, we have throw_err_* macros for this.

Input argument for tcx.lit_to_const.

State of a local variable including a memoized layout

A MemPlace with its layout. Constructing it is only possible in this module.

Represents a pointer in the Miri engine.

State for tracking recursive validation of references

“Relocations” stores the provenance information of pointers stored in memory.

Information about a size mismatch.

Details of an access to uninitialized bytes where it is not allowed.


Used by get_size_and_align to indicate whether the allocation needs to be live.

Details of why a pointer had to be in-bounds.

Represents a constant value in Rust. Scalar and Slice are optimizations for array length computations, enum discriminants and the pattern matching logic.

Extra things to check for during validation of CTFE results.

The value of a function pointer.

An allocation in the global (tcx-managed) memory can be either a function pointer, a static, or a “real” allocation with some data in it.

An Immediate represents a single immediate self-contained Rust value.

A contiguous chunk of initialized or uninitialized memory.

Error information for when the program we executed turned out not to actually be a valid program. This cannot happen in stand-alone Miri, but it can happen during CTFE/ConstProp where we work on generic code or execution does not have all information available.

Error type for tcx.lit_to_const.

Current value of a local variable

Information required for the sound usage of a MemPlace.

An Operand is the result of computing a mir::Operand. It can be immediate, or still in memory. The latter is an optimization, to delay reading that chunk of memory and to avoid having to store arbitrary-sized data here.

Error information for when the program exhausted the resources granted to it by the interpreter.

A Scalar represents an immediate, primitive value existing outside of a memory::Allocation. It is in many ways like a small chunk of an Allocation, up to 16 bytes in size. Like a range of bytes in an Allocation, a Scalar can either represent the raw bytes of a simple value or a pointer into another Allocation

Data returned by Machine::stack_pop, to provide further control over the popping of the stack frame

Unwind information.

Error information for when the program caused Undefined Behavior.

Error information for when the program did something that might (or might not) be correct to do according to the Rust spec, but due to limitations in the interpreter, the operation could not be carried out. These limitations can differ between CTFE and the Miri engine, e.g., CTFE does not support dereferencing pointers at integral addresses.


The functionality needed by memory to manage its allocations

Methods of this trait signifies a point where CTFE evaluation would fail and some use case dependent behaviour can instead be applied.

A trait for machine-specific errors (or other “machine stop” conditions).

Whether this kind of memory is allowed to leak

This trait abstracts over the kind of provenance that is associated with a Pointer. It is mostly opaque; the Machine trait extends it with some more operations that also have access to some global state. We don’t actually care about this Debug bound (we use Provenance::fmt to format the entire pointer), but derive adds some unnecessary bounds.


Free-starting constructor for less syntactic overhead.

Gets the bytes of a constant slice value.

Intern ret and everything it references.

Type Definitions