This rule is common for safety critical software and appears
in most coding guidelines. The reason is simple: memory allocators,
such as malloc, and garbage collectors often have unpredictable
behavior that can significantly impact performance.
A notable class of coding errors also stems from mishandling of
memory allocation and free routines: forgetting to free memory
or continuing to use memory after it was freed, attempting to
allocate more memory than physically available, overstepping
boundaries on allocated memory, etc. Forcing all applications
to live within a fixed, pre-allocated, area of memory can
eliminate many of these problems and make it easier to verify
Note that the only way to dynamically claim memory in the
absence of memory allocation from the heap is to use stack memory.
In the absence of recursion (Rule One),
an upper-bound on the use of stack memory can derived statically,
thus making it possible to prove that an application will always
live within its pre-allocated memory means.