Under specific conditions, the stack frame (entry and exit code for the routine, see section section
6.3, page 404) will be omitted, and the variable will directly be accessed via the stack
pointer.
Conditions for omission of the stack frame:
The target CPU is x86 or ARM.
The -O2 or -OoSTACKFRAME command line switch must be specified.
No inline assembler is used.
No exceptions are used.
No routines are called with outgoing parameters on the stack.