UNPROTECT        2620 gc/os_dep.c            UNPROTECT(h, GC_page_size);
UNPROTECT        2686 gc/os_dep.c        UNPROTECT(h_trunc, (ptr_t)h_end - (ptr_t)h_trunc);
UNPROTECT        2946 gc/os_dep.c        UNPROTECT(start_block,
UNPROTECT        3883 gc/os_dep.c            UNPROTECT(h, GC_page_size);