Pass down "stack start" variables from closer to the top of the stack

The implementation of `native_thread_init_stack` for the various
threading models can use the address of a local variable as part of the
calculation of the machine stack extents:

* pthreads uses it as a lower-bound on the start of the stack, because
  glibc (and maybe other libcs) can store its own data on the stack
  before calling into user code on thread creation.
* win32 uses it as an argument to VirtualQuery, which gets the extent of
  the memory mapping which contains the variable

However, the local being used for this is actually allocated _inside_
the `native_thread_init_stack` frame; that means the caller might
allocate a VALUE on the stack that actually lies outside the bounds
stored in machine.stack_{start,end}.

A local variable from one level above the topmost frame that stores
VALUEs on the stack must be drilled down into the call to
`native_thread_init_stack` to be used in the calculation. This probably
doesn't _really_ matter for the win32 case (they'll be in the same
memory mapping so VirtualQuery should return the same thing), but
definitely could matter for the pthreads case.

[Bug #20001]

1 files changed, 2 insertions, 2 deletions

diff --git a/thread_none.c b/thread_none.c
index 4d53d3bf4d..767b929cf9 100644
--- a/thread_none.c
+++ b/thread_none.c
@@ -140,12 +140,12 @@ ruby_mn_threads_params(void)
 }
 
 void
-ruby_init_stack(volatile VALUE *addr)
+ruby_init_stack(volatile void *addr)
 {
 }
 
 static int
-native_thread_init_stack(rb_thread_t *th)
+native_thread_init_stack(rb_thread_t *th, void *local_in_parent_frame)
 {
 #if defined(__wasm__) && !defined(__EMSCRIPTEN__)
     th->ec->machine.stack_start = (VALUE *)rb_wasm_stack_get_base();