The copy constructors are causing problems when the `fiber.stack` vector
gets reallocated when its capacity is full, since when vectors are
reallocated, the elements are moved (or copied if there's no usable move
constructor) to the reallocated memory and then the original elements
are destroyed.
This premature calling of destructors leads to double-free and
use-after-free errors.
I fixed it by deleting the copy constructors and explicitly defining
move constructors.
Not sure why, but this fixes crashes when calling variadic functions in
the Ruby API in libretro builds when Ruby is built without `-DNDEBUG`.
Maybe the previous way of calling varargs functions was undefined
behaviour somehow.
`rb_rescue` only catches `StandardError`s, which doesn't include things
like Ruby syntax errors that we'd like to catch. We need to explicitly
use `rb_rescue2` to catch `Exception` in order to catch everything.
Okay, the coroutine implementation of `sandbox_malloc` is clearly
broken. It would be working if Asyncify instrumented the `memory.grow`
WebAssembly instruction, but it doesn't instrument it.
This commit reverts commit 42c4ff9497 and
also increases the default VM memory allocation from 64 MiB to 96 MiB to
account for the lack of ability to increase the memory allocation at run
time. I'll find some new way to implement increasing the memory
allocation later.
In release 1.0 of the WebAssembly Specification, it says that all the
bytes in WebAssembly memory need to be initialized to 0 on creation of
the memory, and when memory is grown, the new bytes also need to be
initialized to 0.
It seems this zeroing behaviour is indeed required for the sandbox to
operate correctly. Not zeroing leads to undefined behaviour. This
manifested as a crash that occurred when restarting the libretro core,
but for some reason, only on Emscripten. Not sure why this didn't happen
on other platforms. Even sanitizers weren't able to detect the bug!
(cherry picked from commit edf061e323b8f0ab0c6a72c76ae7ccc07a1649c0)
