Struct VlaDef 

pub struct VlaDef {
    pub object: ObjectId,
    pub storage: ObjectId,
    pub count: Expr,
    pub align: Option<u64>,
    pub range: SourceRange,
}

A variably modified object’s definition: T a[n];, T a[n][m];.

C99 6.7.5.2 gives the object automatic storage duration, a size fixed when the declaration is reached, and the lifetime of the block it is written in; each bound is evaluated exactly once, where the declaration stands, and lives in a hidden size_t object the type points at. This crate emulates the storage with a per-function bump arena on the heap — the elements are bumped off it, and a hidden frame guard whose Drop moves the arena back down is that lifetime — so the one definition becomes a Stmt::Let per bound followed by two more bindings:

let __cinrs_vla_len_a: size_t = <n>;                     // one per bound
let __cinrs_vla_frame_a = __cinrs_vla.frame();          // frame
let mut a: *mut T = __cinrs_vla.alloc::<T>(count);       // object

From there the object is a pointer to the first element: decay is the identity, a[i] is pointer indexing scaled by the run-time size of a row, and sizeof a is the product of the bounds times the element size — see Types::vm_step_ty for what “element” means once more than one dimension is variable.

Fields

object: ObjectId

The object the C program declared, whose type is the array type and whose generated binding is a pointer to the first element.

storage: ObjectId

The hidden frame that gives the elements back; see Object::vla_storage.

count: Expr

The number of elements to allocate: the product of every dimension, read out of the hidden bound objects, in units of the storage’s element type.

align: Option<u64>

The alignment _Alignas(N) or __attribute__((aligned(N))) asked for, when it is stricter than the element type’s: the arena then pads its position to the first address that is a multiple of it.

range: SourceRange

Where the declarator was written.

Trait Implementations

impl Clone for VlaDef

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for VlaDef

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.