Currently the stack limit margin is hard-coded in each port's call to
`mp_stack_set_limit()`, but on threaded ports it's fiddlier and can lead to
bugs (such as incorrect thread stack margin on esp32).
This commit provides a new API to initialise the C Stack in one function
call, with a config macro to set the margin. Where possible the new call
is inlined to reduce code size in thread-free ports.
Intended replacement for `MP_TASK_STACK_LIMIT_MARGIN` on esp32.
The previous `stackctrl.h` API is still present and unmodified apart from a
deprecation comment. However it's not available when the
`MICROPY_PREVIEW_VERSION_2` macro is set.
This work was funded through GitHub Sponsors.
Signed-off-by: Angus Gratton <angus@redyak.com.au>
Header files that are considered internal to the py core and should not
normally be included directly are:
py/nlr.h - internal nlr configuration and declarations
py/bc0.h - contains bytecode macro definitions
py/runtime0.h - contains basic runtime enums
Instead, the top-level header files to include are one of:
py/obj.h - includes runtime0.h and defines everything to use the
mp_obj_t type
py/runtime.h - includes mpstate.h and hence nlr.h, obj.h, runtime0.h,
and defines everything to use the general runtime support functions
Additional, specific headers (eg py/objlist.h) can be included if needed.
I.e. in this mode, C stack will never be used to call a Python function,
but if there's no free heap for a call, it will be reported as
RuntimeError (as expected), not MemoryError.
This patch consolidates all global variables in py/ core into one place,
in a global structure. Root pointers are all located together to make
GC tracing easier and more efficient.
Such mechanism is important to get stable Python functioning, because Python
function calling is handled with C stack. The idea is to sprinkle
STACK_CHECK() calls in places where there can be C recursion.
TODO: Add more STACK_CHECK()'s.
