xpui-cpp-abi

The two ABI boundaries this repository owns, checked on every run.

Using it

Five boundaries cross between Rust and C++ in this organisation. Three belong to the backend and are checked in xpui-backends; these two cross into the application, so they are checked here:

Header	Defined by	Declared by	Who calls
cpp_host/cpp/xpui_host.h	cpp/host_*.cpp	cpp_host/src/raw.rs	Rust calls C++
cpp_host/cpp/xpui_app.h	cpp_host/src/lib.rs, and what register_screen! generates	the header itself	C++ calls Rust

The second is the awkward one. No Rust file spells those signatures out — the only place they exist is the macro's own body, in another repository — so xpui-fui exports its source as a &'static str and this crate parses that. A git dependency lands in a cargo checkout directory with no path a sibling can name, which is why a string and not a file.

What it catches that a link does not: C has no mangling, so two swapped parameters resolve perfectly and corrupt the call frame. symbols_agree in xtask/src/boundary.rs compares which symbols exist; this compares what they are. Neither subsumes the other, and a symbol wrong in the second way is a rendering fault somewhere unrelated.

Checking it

cargo test -p xpui-cpp-abi

The gate runs the same thing under tests.