Python 3.14 stack overflow detection is incompatible with C++ Boost make_fcontext() coroutines

Python 3.14 introduced a new stack overflow detection mecanism: InternalDocs/stack_protection.md (#130396).

The KiCad application uses C++ Boost make_fcontext() coroutines which runs coroutine in their own stack.

Code example from fcontext doc:

// context-function
void f(intptr);

// creates a new stack
std::size_t size = 8192;
void* sp(std::malloc(size));

// context fc uses f() as context function
// fcontext_t is placed on top of context stack
// a pointer to fcontext_t is returned
fcontext_t fc(make_fcontext(sp,size,f));

_Py_InitializeRecursionLimits() is called in the main thread, whereas _Py_CheckRecursiveCall() is called for the first time in a coroutine (make_fcontext()).

Problem: Python detects a stack overflow because it's not aware that the stack base address and size changed when make_fcontext() was called.

pthread functions such as pthread_attr_getguardsize() are incompatible with make_fcontext().

cc @markshannon

Linked PRs

• gh-139667
• gh-139668
• gh-141551
• gh-141661
• gh-141711
• gh-141892
• gh-141944

Start with InternalDocs/stack_protection.md, then trace _Py_InitializeRecursionLimits() and the first _Py_CheckRecursiveCall() from a Boost make_fcontext() coroutine. Review the linked PRs to understand the current direction and whether the stack-base and size transition is already addressed; done means coroutine stacks no longer trigger a false stack-overflow detection.