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The C and C++ Libraries

4.9.4 __user_initial_stackheap()

Returns the locations of the initial stack and heap.

Syntax

__value_in_regs struct __initial_stackheap__user_initial_stackheap (unsigned

R0, unsigned SP, unsigned R2, unsigned SL)

Implementation

Note

If you are using scatter-loading files with the linker, you must reimplement this

function. The default implementation uses the value of the symbol

Image$$ZI$$Limit

This symbol is not defined if the linker uses a scatter-loading file (

-scatter

command-line option).

If this function is redefined, it must:

• use no more than 96 bytes of stack

• not corrupt registers other than r12 (ip)

• return in r0-r3 respectively the heap base, stack base, heap limit, and stack limit

• maintain 8-byte alignment of the heap.

For the default single region model, the values in r2 and r3 are ignored and all memory

between r0 and r1 is available for the heap. For a two region model, the heap limit is set

by r2 and the stack limit is set by r3.

The values of sp and sl inherited from the environment are passed as arguments in r1

and r3, respectively. The default implementation of

__user_initial_stackheap()

that

uses the semihosting SWI SYS_HEAPINFO is given by the library in module

sys_stackheap.o

To create a version of

__user_initial_stack_heap()

that inherits sp and sl from the

execution environment and does not have a heap, set r0 and r2 to the value of r3 and

return.

The definition of

__initial_stackheap

rt_misc.h

is:

struct __initial_stackheap{

unsigned heap_base, stack_base, heap_limit, stack_limit;}

See also the re-implementation of this function in

\Examples\Embedded\embed\retarget.c

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ARM VERSION 1.2 Scheda Tecnica Pagina 159