4 ms·

Right. And of course, it's not just Windows. For example the Linux syscall aio_read() similarly registers a user address with the kernel for later, asynchronou

• ryao 2y ago
  While I am not aware of a Linux syscall that would be equivalent to QueueUserAPC() to allow this to happen, the kernel writing to stack memory is not the problem here. The problem is that a C++ exception was invoked and it unwound a C stack frame. C++ exceptions that unwind C stack frames invoke undefined behavior, so the real solution is to avoid passing function pointers to C++ functions not marked noexcept to C functions as callbacks. It is rather unusual that Windows permits execution on the thread while the kernel is supposed to give it a return value. Writing to the stack is not how I would expect a return value to be passed. Presumably, had the stack frame not been unwound, things would have been fine, unless there is a horrific bug in Windows that should have been obvious when QueueUserAPC() was first implemented. Anyway, it is a shame that the compiler does not issue a warning when you do this. I filed bug reports with both GCC and LLVM requesting that they issue warnings, which should be able to avoid this mess if the compilers issue them and developers heed them: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118263 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118263 https://github.com/llvm/llvm-project/issues/121427 https://github.com/llvm/llvm-project/issues/121427