ATCA_NO_HEAP does not cover the custom-HAL allocation in hal_iface_init()

Affected versions

• v3.8.0 (d49c7d5)

Configuration

Bare-metal target (no heap), built with:

-DATCA_NO_HEAP=ON -DATCA_HAL_CUSTOM=ON

Problem

With ATCA_NO_HEAP defined, the library is documented (and annotated) to perform no
dynamic memory allocation. However, hal_iface_init() (lib/hal/atca_hal.c) allocates the custom-HAL
function-pointer struct unconditionally when ATCA_CUSTOM_IFACE is used
(lib/hal/atca_hal.c:306-308, v3.8.0):

#ifdef ATCA_HAL_CUSTOM
        if (ATCA_CUSTOM_IFACE == cfg->iface_type)
        {
            *hal = hal_malloc(sizeof(ATCAHAL_t));   /* not gated by ATCA_NO_HEAP */

Observed behaviour

On a heapless target (malloc returns NULL), atcab_init() with a
custom-HAL ATCAIfaceCfg fails with ATCA_ALLOC_FAILURE.

Expected behaviour

With ATCA_NO_HEAP defined, no code path calls hal_malloc/hal_free.

Suggested fix

When using ATCA_NO_HEAP, use a static ATCAHAL_t instance in hal_iface_init() .