Stream: git-wasmtime

Topic: wasmtime / PR #14895 [DO NOT REVIEW] Add a fuzzer for com...

Wasmtime GitHub notifications bot (Oct 21 2026 at 00:26):

jrandolf opened PR #14895 from jrandolf:fuzz-implements to bytecodealliance:main:

This adds a component_implements fuzzer, run by the misc fuzz target, for the implements and external-id name annotations. It supersedes #14802, which only toggled implements on and off in the component_api fuzzer.

It generates components of many shapes:

• WIT packages come from wit-smith, and the world either comes from wit-smith or is generated over its interfaces. Interfaces are imported and exported both by their own names and under labels, often several labels for one interface.
• Every world item, function and type gets a random external-id or none.
• A core module is generated where most exports forward to a random import of the same type. wit-component turns it into a component, optionally with canonical names.
• Optionally, the component is nested in an outer one that instantiates it, possibly swapping labels of the same interface, and re-exports everything.

It then checks that:

• component_type() has exactly the expected imports and exports, with the right implements and external-id, before and after serialize/deserialize.
• is_implements matches the interface and its semver-compatible versions, and nothing else.
• A Linker missing an import fails to instantiate, even if the implemented interface is defined under its own name.
• Each call to a forwarding export reaches exactly the import it's wired to, including when another import is stubbed with define_unknown_imports_as_{traps,default_values}.

It ran for 40 minutes, and for 30 minutes under AddressSanitizer, without failures. One case is skipped with a FIXME: with canonical names, is_implements doesn't match the full version of an interface whose version has build metadata but no semver-compatible track (0.0.x or a prerelease), because the version-suffix of names isn't kept.

Run it with FUZZER=component_implements cargo +nightly fuzz run misc.

Wasmtime GitHub notifications bot (Oct 21 2026 at 02:05):

:cross_mark: jrandolf closed without merge PR #14895.

Last updated: Oct 31 2026 at 23:03 UTC