Reserve stack space on non-main threads for crash recovery on Windows

src/crystal/system/win32/thread.cr

@@ -12,13 +12,24 @@ module Crystal::System::Thread
     @system_handle = GC.beginthreadex(
       security: Pointer(Void).null,
       stack_size: LibC::UInt.zero,
-      start_address: ->(data : Void*) { data.as(::Thread).start; LibC::UInt.zero },
+      start_address: ->Thread.thread_proc(Void*),
       arglist: self.as(Void*),
       initflag: LibC::UInt.zero,
       thrdaddr: Pointer(LibC::UInt).null,
     )
   end
 
+  def self.thread_proc(data : Void*) : LibC::UInt
+    # ensure that even in the case of stack overflow there is enough reserved
+    # stack space for recovery (for the main thread this is done in
+    # `Exception::CallStack.setup_crash_handler`)
+    stack_size = Crystal::System::Fiber::RESERVED_STACK_SIZE
+    LibC.SetThreadStackGuarantee(pointerof(stack_size))
+
+    data.as(::Thread).start
+    LibC::UInt.zero
+  end
+
   def self.current_handle : Handle
     # `GetCurrentThread` returns a _constant_ and is only meaningful as an
     # argument to Win32 APIs; to uniquely identify it we must duplicate the handle

src/exception/call_stack/stackwalk.cr

@@ -51,7 +51,8 @@ struct Exception::CallStack
     end)
 
     # ensure that even in the case of stack overflow there is enough reserved
-    # stack space for recovery
+    # stack space for recovery (for other threads this is done in
+    # `Crystal::System::Thread.thread_proc`)
     stack_size = Crystal::System::Fiber::RESERVED_STACK_SIZE
     LibC.SetThreadStackGuarantee(pointerof(stack_size))
   end