Struct wasmtime_runtime::VMExternRefActivationsTable

#[repr(C)]
pub struct VMExternRefActivationsTable { /* private fields */ }

A table that over-approximizes the set of VMExternRefs that any Wasm activation on this thread is currently using.

Under the covers, this is a simple bump allocator that allows duplicate entries. Deduplication happens at GC time.

Implementations

impl VMExternRefActivationsTable

pub fn new() -> Self

Create a new VMExternRefActivationsTable.

pub fn bump_capacity_remaining(&self) -> usize

Get the available capacity in the bump allocation chunk.

pub fn try_insert(&mut self, externref: VMExternRef) -> Result<(), VMExternRef>

Try and insert a VMExternRef into this table.

This is a fast path that only succeeds when the bump chunk has the capacity for the requested insertion.

If the insertion fails, then the VMExternRef is given back. Callers may attempt a GC to free up space and try again, or may call insert_slow_path to infallibly insert the reference (potentially allocating additional space in the table to hold it).

pub unsafe fn insert_with_gc(
    &mut self,
    externref: VMExternRef,
    module_info_lookup: &dyn ModuleInfoLookup
)

Insert a reference into the table, falling back on a GC to clear up space if the table is already full.

Unsafety

The same as gc.

pub fn insert_without_gc(&mut self, externref: VMExternRef)

Insert a reference into the table, without ever performing GC.

pub fn stack_canary(&self) -> Option<usize>

Fetches the current value of this table’s stack canary.

This should only be used in conjunction with setting the stack canary below if the return value is None typically. This is called from RAII guards in wasmtime::func::invoke_wasm_and_catch_traps.

For more information on canaries see the gc functions below.

pub fn set_stack_canary(&mut self, canary: Option<usize>)

Sets the current value of the stack canary.

This is called from RAII guards in wasmtime::func::invoke_wasm_and_catch_traps. This is used to update the stack canary to a concrete value and then reset it back to None when wasm is finished.

For more information on canaries see the gc functions below.

pub fn set_gc_okay(&mut self, okay: bool) -> bool

Set whether it is okay to GC or not right now.

This is provided as a helper for enabling various debug-only assertions and checking places where the wasmtime-runtime user expects there not to be any GCs.