From the change:
// xtensa has more registers than an instruction can address. The 16 that
// can be addressed are called the "window". When a function is called or
// returns the window rotates. This allows for more efficient function calls
// because ram doesn't need to be used. It's only used if the window wraps
// around onto itself. At that point values are "spilled" to empty spots in
// the stack that were set aside. When the window rotates back around (on
// function return), the values are restored into the register from ram.
// So, in order to read the values in the stack scan we must make sure all
// of the register values we care about have been spilled to RAM. Luckily,
// there is a HAL call to do it. There is a bit of a race condition here
// because the register value could change after it's been restored but that
// is unlikely to happen with a heap pointer while we do a GC.
Fixes#2907
* Fix flash writes that don't end on a sector boundary. Fixes#2944
* Fix enum incompatibility with IDF.
* Fix printf output so it goes out debug UART.
* Increase stack size to 8k.
* Fix sleep of less than a tick so it doesn't crash.
Diego Elio Pettenò
Scott Shawcroft
jerryneedell