Assert parking lots have no suspended waiters at destruction

[jeet-dekivadia]

Summary

• assert that a ParkingLotImpl is empty before its intrusive wait queue is destroyed
• extend the lifetime check already present on Channel to Event, Semaphore, and ParkingLot
• surface misuse at the destruction site instead of silently unlinking suspended awaiters and leaving their tasks stranded

Validation

• git diff --check
• printf '#include "corral/corral.h"\\nint main() { corral::Event e; corral::Semaphore s; corral::ParkingLot p; }\\n' | clang++ -std=c++20 -fsyntax-only -I. -x c++ -
• cmake -S . -B build -DCMAKE_C_COMPILER=gcc-14 -DCMAKE_CXX_COMPILER=g++-14 -DCORRAL_BOOST=/opt/include -DCORRAL_CATCH2=https://github.com/catchorg/catch2
• cmake --build build -j2
• ctest --test-dir build --output-on-failure
• focused Linux harness: empty destruction exited 0; destruction with one parked waiter reached the custom CORRAL_ASSERT handler with exit 42

[jeet-dekivadia]

Small follow-up for review context. This extends the existing Channel lifetime defense to the shared parking-lot base used by Event, Semaphore, and ParkingLot. Destroying a lot while a coroutine is still parked otherwise leaves an intrusive waiter behind; asserting at destruction makes that misuse deterministic at the ownership boundary.

Validation from preparation: git diff --check; clang++ -std=c++20 -fsyntax-only probe including corral/corral.h and constructing Event, Semaphore, and ParkingLot; GCC 14 configure, build, and CTest; and a focused harness that exited 0 for empty destruction and reached the custom CORRAL_ASSERT path with exit 42 for one parked waiter.