unknown check_stack option
An unknown option was given with the old form of the check_stack pragma. With the old form, the argument to the pragma must be empty, +, or -.
The current state of stack checking was left unchanged.
For example, the following generates this warning:
#pragma check_stack yes
The following code corrects this situation:
#pragma check_stack + // Old form
or
#pragma check_stack (on) // New form