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0305c1ace7
1. No timeout → wait_for + 30 s default (ffi/codegen/cpp.nim)
ffi_call_ now takes std::chrono::milliseconds timeout and uses cv.wait_for. All factory/method signatures carry a timeout parameter (default std::chrono::seconds{30}), mirroring the Rust blocking API.
2. Stack-allocated state → shared_ptr ownership (ffi/codegen/cpp.nim)
ffi_cb_ now receives a heap-allocated std::shared_ptr<FfiCallState_>* as user_data. The refcount is 2 going in (one for ffi_call_, one for the callback). If ffi_call_ times out and returns, its copy drops — but the state stays alive (refcount 1) until Nim eventually calls back and delete sptr in ffi_cb_ drops the last reference. No more stack UAF.
3. Destructor + Rule of 5 (ffi/codegen/cpp.nim, examples/nim_timer/nim_timer.nim)
Added nimtimer_destroy to nim_timer.nim with {.dynlib, exportc, cdecl, raises: [].} — joins the FFI and watchdog threads, frees the context
Codegen now always emits void {libName}_destroy(void* ctx) in extern "C" and generates a destructor, deleted copy ctor/assignment, and move ctor/assignment for the context class
timeout_ stored in the class; move transfers it, destructor uses it
4. Hardcoded TimerConfig in createAsync (ffi/codegen/cpp.nim)
createAsync now uses the actual ctorParams list (same as create), so it's correct for any library, not just nim_timer.
5. Opaque exceptions → clear error messages (ffi/codegen/cpp.nim)
deserializeFfiResult wraps nlohmann::json::parse + .get<T>() in a catch that rethrows as "FFI response deserialization failed: ...". The stoull in create() is also try-caught with "FFI create returned non-numeric address: " + raw.
nim_timer example
This example is a self-contained Nimble project demonstrating how to import nim-ffi and use the .ffiCtor. / .ffi. abstraction.
Usage
-
Change into the example directory:
cd examples/nim_timer -
Install the local
ffidependency:nimble install -y ../.. -
Build the example library:
nimble build -
Generate bindings:
nimble genbindings_rust nimble genbindings_cpp
Rust example clients
The Rust client lives in examples/nim_timer/rust_client.
-
Run the sync example:
cd examples/nim_timer/rust_client cargo run --bin rust_client -
Run the Tokio example:
cd examples/nim_timer/rust_client cargo run --bin tokio_client
C++ example
The generated C++ example lives in examples/nim_timer/cpp_bindings.
Build and run it with:
cd examples/nim_timer/cpp_bindings
cmake -S . -B build
cmake --build build
./build/example