start2_addr      1923 gc/os_dep.c        ptr_t start2_addr = GC_unmap_start(start2, bytes2);
start2_addr      1926 gc/os_dep.c        ptr_t end_addr = start2_addr;
start2_addr      1930 gc/os_dep.c        if (0 == start2_addr) end_addr = GC_unmap_end(start1, bytes1 + bytes2);