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> There shall be no direct or indirect use of recursive function calls. > [The] absence of recursion prevents runaway code, and helps to secure predictable per

• projectileboy 11y ago
  Well, when your code runs on an interplanetary spacecraft, you tend to be extra cautious.
  • mturmon 11y ago
    Yes, these guidelines do not dictate how ground software, and especially research codes, are written at JPL. See the section of the doc under "Scope."
• dahart 11y ago
  That sorta goes hand-in-hand with "There shall be no use of dynamic memory allocation after task initialization." Which in my experience is the harder rule to deal with. It's not that often that you really truly need recursion. It happens, just not often. But no allocations, that radically changes how one codes. But, these rules are for safety on embedded systems with very small amounts of memory. These represent the best lessons learned, the best ways to guarantee your function will finish in finite time and not run out of memory.
  • fsloth 11y ago
    "But no allocations, that radically changes how one codes." But this does not forbid implementing ones own memory manager that uses blocks from a huge continuous buffer.
    • dahart 11y ago
      True. Though I don't work at JPL or speak to what they would allow or forbid, but if you did implement your own memory manager, I imagine that you'd still need to write code that guarantees it will never run out, which might be harder to do if you have this abstraction. The spirit of these rules is to be enable code writing that is obviously correct and finite in time and space, at a glance. So I'm in pure speculation land here, but I could see JPL frowning on rolling your own memory manager. Though I also imagine many applications of these rules happen on hardware that is small enough to make writing a memory manager overkill anyway.