Defined in rt_misc.h, __user_initial_stackheap() is
supported for backwards compatibility with earlier versions of the
ARM C and C++ libraries.
Note
ARM recommends that you use __user_setup_stackheap() in
preference to __user_initial_stackheap().
The differences between __user_initial_stackheap() and __user_setup_stackheap() are:
__user_initial_stackheap()receives the stack pointer (containing the same value it had on entry to__main()) inr1, and is expected to return the new stack base inr1.__user_setup_stackheap()receives the stack pointer insp, and returns the stack base insp.__user_initial_stackheap()is provided with a small temporary stack to run on. This temporary stack enables__user_initial_stackheap()to be implemented in C, providing that it uses no more than 88 bytes of stack space.__user_setup_stackheap()has no temporary stack and cannot usually be implemented in C.
Using __user_setup_stackheap() instead
of __user_initial_steakheap() reduces code
size, because __user_setup_stackheap() has
no requirement for a temporary stack.
In the following circumstances you cannot use the provided __user_setup_stackheap() function, but
you can use the __user_initial_stackheap() function:
your implementation is sufficiently complex that it warrants the use of a temporary stack when setting up the initial heap and stack
you have a requirement to implement the heap and stack creation code in C rather than in assembly language.
See also- Reference
ARM C and C++ Libraries and Floating-Point Support Reference:
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