Most versions of the C library include a function, alloca, that dynamically allocates space within the current stack frame.2 It has two advantages over the usual malloc, which allocates space in the heap: it’s usually very fast, and the space it allocates is reclaimed automatically when the current subroutine returns. Assuming the programmer wants deallocation to happen then, it’s convenient to be able to skip the explicit free operations. How might you implement alloca in conjunction with the calling conventions of our various case studies?