Day: July 11, 2017

Comparing NuttX with Zephyr

Today I decided to do a basic test comparing a small NuttX hello-world against the zephyr hello-world.

First let explain that I’m a NuttX contributor and maybe I’m a little bit biased, but I tried to keep me (as much as I could) neutral on this.

What motivated to do that was the nice Eric Styger article: https://mcuoneclipse.com/2017/01/22/zephyr-thoughts-and-first-steps-on-the-arm-cortex-m4f-with-gcc-gdb-and-eclipse/

I like the part that Eric said:

“I’m really not sure how Intel has convinced the Linux Foundation to promote Zephyr. If someone is looking for an operating system with Linux heritage, then it would something like NuttX or eCos in my view. On the other hand: more free and open source choices are good :-).”

(Hey Eric, we need you on NuttX!)

Let’s to start our test, first (of course) NuttX:

$ git clone https://www.bitbucket.org/nuttx/nuttx nuttx-project
$ git clone https://www.bitbucket.org/nuttx/apps
$ cd nuttx-project/
$ ./tools/configure.sh stm32f103-minimum/hello
  Copy files
  Refreshing...

$ make
make[1]: Entering directory '/home/alan/nuttx-project/tools'
make[1]: Leaving directory '/home/alan/nuttx-project/tools'
No .version file found, creating one
make[1]: Entering directory '/home/alan/nuttx-project/tools'
make[1]: Leaving directory '/home/alan/nuttx-project/tools'
LN: include/arch to arch/arm/include
LN: include/arch/board to /home/alan/nuttx-project/configs/stm32f103-minimum/include
LN: include/arch/chip to arch/arm/include/stm32
LN: arch/arm/src/board to /home/alan/nuttx-project/configs/stm32f103-minimum/src
LN: arch/arm/src/chip to arch/arm/src/stm32
make[1]: Entering directory '/home/alan/nuttx-project/configs'
make[1]: Leaving directory '/home/alan/nuttx-project/configs'
make[1]: Entering directory '/home/alan/apps'
make[2]: Entering directory '/home/alan/apps/platform'
LN: platform/board to /home/alan/apps/platform/dummy
make[2]: Leaving directory '/home/alan/apps/platform'
make[1]: Leaving directory '/home/alan/apps'
make[1]: Entering directory '/home/alan/nuttx-project/configs'
make[2]: Entering directory '/home/alan/nuttx-project/configs/stm32f103-minimum/src'
make[2]: Nothing to be done for 'context'.
make[2]: Leaving directory '/home/alan/nuttx-project/configs/stm32f103-minimum/src'
make[1]: Leaving directory '/home/alan/nuttx-project/configs'
make[1]: Entering directory '/home/alan/apps'
make[2]: Entering directory '/home/alan/apps/builtin'
make[3]: Entering directory '/home/alan/apps/builtin/registry'
make[3]: Leaving directory '/home/alan/apps/builtin/registry'
make[2]: Leaving directory '/home/alan/apps/builtin'
make[2]: Entering directory '/home/alan/apps'
make[3]: Entering directory '/home/alan/apps/examples/hello'
make[3]: Nothing to be done for 'context'.
make[3]: Leaving directory '/home/alan/apps/examples/hello'
make[3]: Entering directory '/home/alan/apps/examples/nsh'
make[3]: Nothing to be done for 'context'.
make[3]: Leaving directory '/home/alan/apps/examples/nsh'
make[3]: Entering directory '/home/alan/apps/nshlib'
make[3]: Nothing to be done for 'context'.
make[3]: Leaving directory '/home/alan/apps/nshlib'
make[3]: Entering directory '/home/alan/apps/system/readline'
make[3]: Nothing to be done for 'context'.
make[3]: Leaving directory '/home/alan/apps/system/readline'
make[3]: Entering directory '/home/alan/apps/platform'
LN: platform/board to /home/alan/apps/platform/dummy
make[3]: Leaving directory '/home/alan/apps/platform'
make[2]: Leaving directory '/home/alan/apps'
make[1]: Leaving directory '/home/alan/apps'
make[1]: Entering directory '/home/alan/nuttx-project/tools'
make[1]: Leaving directory '/home/alan/nuttx-project/tools'
make[1]: Entering directory '/home/alan/nuttx-project/tools'
make[1]: Leaving directory '/home/alan/nuttx-project/tools'
make[1]: Entering directory '/home/alan/nuttx-project/sched'
make[1]: Leaving directory '/home/alan/nuttx-project/sched'
make[1]: Entering directory '/home/alan/nuttx-project/drivers'
make[1]: Leaving directory '/home/alan/nuttx-project/drivers'
make[1]: Entering directory '/home/alan/nuttx-project/configs'
make[1]: Leaving directory '/home/alan/nuttx-project/configs'
make[1]: Entering directory '/home/alan/nuttx-project/arch/arm/src'
make[2]: Entering directory '/home/alan/nuttx-project/configs/stm32f103-minimum/src'
make[2]: Leaving directory '/home/alan/nuttx-project/configs/stm32f103-minimum/src'
make[1]: Leaving directory '/home/alan/nuttx-project/arch/arm/src'
make[1]: Entering directory '/home/alan/apps'
make[2]: Entering directory '/home/alan/apps/builtin'
make[3]: Entering directory '/home/alan/apps/builtin/registry'
make[3]: Nothing to be done for 'context'.
make[3]: Leaving directory '/home/alan/apps/builtin/registry'
make[2]: Leaving directory '/home/alan/apps/builtin'
make[2]: Entering directory '/home/alan/apps'
make[3]: Entering directory '/home/alan/apps/examples/hello'
make[3]: Nothing to be done for 'context'.
make[3]: Leaving directory '/home/alan/apps/examples/hello'
make[3]: Entering directory '/home/alan/apps/examples/nsh'
make[3]: Nothing to be done for 'context'.
make[3]: Leaving directory '/home/alan/apps/examples/nsh'
make[3]: Entering directory '/home/alan/apps/nshlib'
make[3]: Nothing to be done for 'context'.
make[3]: Leaving directory '/home/alan/apps/nshlib'
make[3]: Entering directory '/home/alan/apps/system/readline'
make[3]: Nothing to be done for 'context'.
make[3]: Leaving directory '/home/alan/apps/system/readline'
make[3]: Entering directory '/home/alan/apps/platform'
LN: platform/board to /home/alan/apps/platform/dummy
make[3]: Leaving directory '/home/alan/apps/platform'
make[2]: Leaving directory '/home/alan/apps'
make[2]: Entering directory '/home/alan/apps/examples/hello'
make[2]: Leaving directory '/home/alan/apps/examples/hello'
make[2]: Entering directory '/home/alan/apps/examples/nsh'
make[2]: Leaving directory '/home/alan/apps/examples/nsh'
make[2]: Entering directory '/home/alan/apps/nshlib'
make[2]: Leaving directory '/home/alan/apps/nshlib'
make[2]: Entering directory '/home/alan/apps/system/readline'
make[2]: Leaving directory '/home/alan/apps/system/readline'
make[2]: Entering directory '/home/alan/apps/platform'
LN: platform/board to /home/alan/apps/platform/dummy
make[2]: Leaving directory '/home/alan/apps/platform'
make[1]: Leaving directory '/home/alan/apps'
make[1]: Entering directory '/home/alan/nuttx-project/libc'
make[1]: Leaving directory '/home/alan/nuttx-project/libc'
make[1]: Entering directory '/home/alan/nuttx-project/mm'
make[1]: Leaving directory '/home/alan/nuttx-project/mm'
make[1]: Entering directory '/home/alan/nuttx-project/fs'
make[1]: Leaving directory '/home/alan/nuttx-project/fs'
make[1]: Entering directory '/home/alan/nuttx-project/binfmt'
make[1]: Leaving directory '/home/alan/nuttx-project/binfmt'
make[1]: Entering directory '/home/alan/nuttx-project/sched'
CC:  clock/clock_initialize.c
CC:  clock/clock_settime.c
CC:  clock/clock_gettime.c
CC:  clock/clock_getres.c
CC:  clock/clock_time2ticks.c
CC:  clock/clock_abstime2ticks.c
CC:  clock/clock_ticks2time.c
CC:  clock/clock_systimer.c
CC:  clock/clock_systimespec.c
CC:  clock/clock_timespec_add.c
CC:  clock/clock_timespec_subtract.c
CC:  errno/errno_getptr.c
CC:  group/group_create.c
CC:  group/group_join.c
CC:  group/group_leave.c
CC:  group/group_find.c
CC:  group/group_setupstreams.c
CC:  group/group_setupidlefiles.c
CC:  group/group_setuptaskfiles.c
CC:  group/group_foreachchild.c
CC:  group/group_killchildren.c
CC:  init/os_start.c
CC:  init/os_bringup.c
CC:  irq/irq_initialize.c
CC:  irq/irq_attach.c
CC:  irq/irq_dispatch.c
CC:  irq/irq_unexpectedisr.c
CC:  paging/pg_miss.c
CC:  paging/pg_worker.c
CC:  sched/sched_garbage.c
CC:  sched/sched_getfiles.c
CC:  sched/sched_addreadytorun.c
CC:  sched/sched_removereadytorun.c
CC:  sched/sched_addprioritized.c
CC:  sched/sched_mergeprioritized.c
CC:  sched/sched_mergepending.c
CC:  sched/sched_addblocked.c
CC:  sched/sched_removeblocked.c
CC:  sched/sched_free.c
CC:  sched/sched_gettcb.c
CC:  sched/sched_verifytcb.c
CC:  sched/sched_releasetcb.c
CC:  sched/sched_getsockets.c
CC:  sched/sched_getstreams.c
CC:  sched/sched_setparam.c
CC:  sched/sched_setpriority.c
CC:  sched/sched_getparam.c
CC:  sched/sched_setscheduler.c
CC:  sched/sched_getscheduler.c
CC:  sched/sched_yield.c
CC:  sched/sched_rrgetinterval.c
CC:  sched/sched_foreach.c
CC:  sched/sched_lock.c
CC:  sched/sched_unlock.c
CC:  sched/sched_lockcount.c
CC:  sched/sched_idletask.c
CC:  sched/sched_self.c
CC:  sched/sched_roundrobin.c
CC:  sched/sched_resumescheduler.c
CC:  sched/sched_processtimer.c
CC:  semaphore/sem_destroy.c
CC:  semaphore/sem_wait.c
CC:  semaphore/sem_trywait.c
CC:  semaphore/sem_tickwait.c
CC:  semaphore/sem_timedwait.c
CC:  semaphore/sem_timeout.c
CC:  semaphore/sem_post.c
CC:  semaphore/sem_recover.c
CC:  semaphore/sem_reset.c
CC:  semaphore/sem_waitirq.c
CC:  task/task_create.c
CC:  task/task_init.c
CC:  task/task_setup.c
CC:  task/task_activate.c
CC:  task/task_start.c
CC:  task/task_delete.c
CC:  task/task_exit.c
CC:  task/task_exithook.c
CC:  task/task_getgroup.c
CC:  task/task_getpid.c
CC:  task/task_prctl.c
CC:  task/task_recover.c
CC:  task/task_restart.c
CC:  task/task_spawnparms.c
CC:  task/task_setcancelstate.c
CC:  task/task_terminate.c
CC:  task/exit.c
CC:  task/task_spawn.c
CC:  wdog/wd_initialize.c
CC:  wdog/wd_create.c
CC:  wdog/wd_start.c
CC:  wdog/wd_cancel.c
CC:  wdog/wd_delete.c
CC:  wdog/wd_gettime.c
CC:  wdog/wd_recover.c
AR:   clock_initialize.o clock_settime.o clock_gettime.o clock_getres.o clock_time2ticks.o clock_abstime2ticks.o clock_ticks2time.o clock_systimer.o clock_systimespec.o clock_timespec_add.o clock_timespec_subtract.o errno_getptr.o group_create.o group_join.o group_leave.o group_find.o group_setupstreams.o group_setupidlefiles.o group_setuptaskfiles.o group_foreachchild.o group_killchildren.o os_start.o os_bringup.o irq_initialize.o irq_attach.o irq_dispatch.o irq_unexpectedisr.o pg_miss.o pg_worker.o sched_garbage.o sched_getfiles.o sched_addreadytorun.o sched_removereadytorun.o sched_addprioritized.o sched_mergeprioritized.o sched_mergepending.o sched_addblocked.o sched_removeblocked.o sched_free.o sched_gettcb.o sched_verifytcb.o sched_releasetcb.o sched_getsockets.o sched_getstreams.o sched_setparam.o sched_setpriority.o sched_getparam.o sched_setscheduler.o sched_getscheduler.o sched_yield.o sched_rrgetinterval.o sched_foreach.o sched_lock.o sched_unlock.o sched_lockcount.o sched_idletask.o sched_self.o sched_roundrobin.o sched_resumescheduler.o sched_processtimer.o sem_destroy.o sem_wait.o sem_trywait.o sem_tickwait.o sem_timedwait.o sem_timeout.o sem_post.o sem_recover.o sem_reset.o sem_waitirq.o task_create.o task_init.o task_setup.o task_activate.o task_start.o task_delete.o task_exit.o task_exithook.o task_getgroup.o task_getpid.o task_prctl.o task_recover.o task_restart.o task_spawnparms.o task_setcancelstate.o task_terminate.o exit.o task_spawn.o wd_initialize.o wd_create.o wd_start.o wd_cancel.o wd_delete.o wd_gettime.o wd_recover.o
make[1]: Leaving directory '/home/alan/nuttx-project/sched'
make[1]: Entering directory '/home/alan/nuttx-project/drivers'
CC:  pipes/pipe.c
CC:  pipes/fifo.c
CC:  pipes/pipe_common.c
CC:  serial/serial.c
CC:  serial/serial_io.c
CC:  serial/lowconsole.c
CC:  syslog/vsyslog.c
CC:  syslog/syslog_stream.c
CC:  syslog/syslog_emergstream.c
CC:  syslog/syslog_channel.c
CC:  syslog/syslog_putc.c
CC:  syslog/syslog_write.c
CC:  syslog/syslog_force.c
CC:  syslog/syslog_flush.c
CC:  syslog/syslog_initialize.c
CC:  syslog/syslog_device.c
CC:  syslog/syslog_consolechannel.c
CC:  usbhost/hid_parser.c
CC:  dev_null.c
CC:  dev_zero.c
AR:   pipe.o fifo.o pipe_common.o serial.o serial_io.o lowconsole.o vsyslog.o syslog_stream.o syslog_emergstream.o syslog_channel.o syslog_putc.o syslog_write.o syslog_force.o syslog_flush.o syslog_initialize.o syslog_device.o syslog_consolechannel.o hid_parser.o dev_null.o dev_zero.o
make[1]: Leaving directory '/home/alan/nuttx-project/drivers'
make[1]: Entering directory '/home/alan/nuttx-project/configs'
AR:    
make[1]: Leaving directory '/home/alan/nuttx-project/configs'
make[1]: Entering directory '/home/alan/nuttx-project/libc'
CC:  dirent/lib_readdirr.c
CC:  dirent/lib_telldir.c
CC:  fixedmath/lib_fixedmath.c
CC:  fixedmath/lib_b16sin.c
CC:  fixedmath/lib_b16cos.c
CC:  fixedmath/lib_b16atan2.c
CC:  fixedmath/lib_ubsqrt.c
CC:  inttypes/lib_imaxabs.c
CC:  inttypes/lib_strtoimax.c
CC:  inttypes/lib_strtoumax.c
CC:  libgen/lib_basename.c
CC:  libgen/lib_dirname.c
CC:  misc/lib_stream.c
CC:  misc/lib_utsname.c
CC:  misc/lib_xorshift128.c
CC:  misc/lib_tea_encrypt.c
CC:  misc/lib_tea_decrypt.c
CC:  misc/lib_umul32.c
CC:  misc/lib_umul64.c
CC:  misc/lib_umul32x64.c
CC:  misc/lib_uadd32x64.c
CC:  misc/lib_uadd64.c
CC:  misc/lib_usub64x32.c
CC:  misc/lib_usub64.c
CC:  misc/lib_sendfile.c
CC:  misc/lib_streamsem.c
CC:  misc/lib_crc64.c
CC:  misc/lib_crc32.c
CC:  misc/lib_crc16.c
CC:  misc/lib_crc8.c
CC:  misc/lib_dumpbuffer.c
CC:  misc/lib_match.c
CC:  net/lib_addrconfig.c
CC:  net/lib_etherntoa.c
CC:  net/lib_htons.c
CC:  net/lib_htonl.c
CC:  net/lib_inetaddr.c
CC:  net/lib_inetntoa.c
CC:  net/lib_inetntop.c
CC:  net/lib_inetpton.c
CC:  queue/sq_addlast.c
CC:  queue/sq_addfirst.c
CC:  queue/sq_addafter.c
CC:  queue/sq_cat.c
CC:  queue/sq_rem.c
CC:  queue/sq_remlast.c
CC:  queue/sq_remfirst.c
CC:  queue/sq_remafter.c
CC:  queue/sq_count.c
CC:  queue/dq_addlast.c
CC:  queue/dq_addfirst.c
CC:  queue/dq_addafter.c
CC:  queue/dq_addbefore.c
CC:  queue/dq_cat.c
CC:  queue/dq_rem.c
CC:  queue/dq_remlast.c
CC:  queue/dq_remfirst.c
CC:  queue/dq_count.c
CC:  sched/sched_getprioritymax.c
CC:  sched/sched_getprioritymin.c
CC:  sched/task_setcanceltype.c
CC:  sched/task_testcancel.c
CC:  semaphore/sem_init.c
CC:  semaphore/sem_getprotocol.c
CC:  semaphore/sem_getvalue.c
CC:  semaphore/sem_setprotocol.c
CC:  spawn/lib_psfa_addaction.c
CC:  spawn/lib_psfa_addclose.c
CC:  spawn/lib_psfa_adddup2.c
CC:  spawn/lib_psfa_addopen.c
CC:  spawn/lib_psfa_destroy.c
CC:  spawn/lib_psfa_init.c
CC:  spawn/lib_psa_getflags.c
CC:  spawn/lib_psa_getschedparam.c
CC:  spawn/lib_psa_getschedpolicy.c
CC:  spawn/lib_psa_init.c
CC:  spawn/lib_psa_setflags.c
CC:  spawn/lib_psa_setschedparam.c
CC:  spawn/lib_psa_setschedpolicy.c
CC:  spawn/lib_psa_getstacksize.c
CC:  spawn/lib_psa_setstacksize.c
CC:  stdio/lib_fileno.c
CC:  stdio/lib_printf.c
CC:  stdio/lib_sprintf.c
CC:  stdio/lib_asprintf.c
CC:  stdio/lib_snprintf.c
CC:  stdio/lib_libsprintf.c
CC:  stdio/lib_vsprintf.c
CC:  stdio/lib_vasprintf.c
CC:  stdio/lib_vsnprintf.c
CC:  stdio/lib_libvsprintf.c
CC:  stdio/lib_dprintf.c
CC:  stdio/lib_vdprintf.c
CC:  stdio/lib_meminstream.c
CC:  stdio/lib_memoutstream.c
CC:  stdio/lib_memsistream.c
CC:  stdio/lib_memsostream.c
CC:  stdio/lib_lowoutstream.c
CC:  stdio/lib_zeroinstream.c
CC:  stdio/lib_nullinstream.c
CC:  stdio/lib_nulloutstream.c
CC:  stdio/lib_sscanf.c
CC:  stdio/lib_rawinstream.c
CC:  stdio/lib_rawoutstream.c
CC:  stdio/lib_rawsistream.c
CC:  stdio/lib_rawsostream.c
CC:  stdio/lib_libnoflush.c
CC:  stdio/lib_libsnoflush.c
CC:  stdio/lib_remove.c
CC:  stdio/lib_fopen.c
CC:  stdio/lib_freopen.c
CC:  stdio/lib_fclose.c
CC:  stdio/lib_fread.c
CC:  stdio/lib_libfread.c
CC:  stdio/lib_fseek.c
CC:  stdio/lib_ftell.c
CC:  stdio/lib_fsetpos.c
CC:  stdio/lib_fgetpos.c
CC:  stdio/lib_fgetc.c
CC:  stdio/lib_fgets.c
CC:  stdio/lib_gets_s.c
CC:  stdio/lib_gets.c
CC:  stdio/lib_libfgets.c
CC:  stdio/lib_fwrite.c
CC:  stdio/lib_libfwrite.c
CC:  stdio/lib_fflush.c
CC:  stdio/lib_libflushall.c
CC:  stdio/lib_libfflush.c
CC:  stdio/lib_rdflush.c
CC:  stdio/lib_wrflush.c
CC:  stdio/lib_fputc.c
CC:  stdio/lib_puts.c
CC:  stdio/lib_fputs.c
CC:  stdio/lib_ungetc.c
CC:  stdio/lib_vprintf.c
CC:  stdio/lib_fprintf.c
CC:  stdio/lib_vfprintf.c
CC:  stdio/lib_stdinstream.c
CC:  stdio/lib_stdoutstream.c
CC:  stdio/lib_stdsistream.c
CC:  stdio/lib_stdsostream.c
CC:  stdio/lib_perror.c
CC:  stdio/lib_feof.c
CC:  stdio/lib_ferror.c
CC:  stdio/lib_clearerr.c
CC:  stdlib/lib_abs.c
CC:  stdlib/lib_abort.c
CC:  stdlib/lib_div.c
CC:  stdlib/lib_ldiv.c
CC:  stdlib/lib_lldiv.c
CC:  stdlib/lib_itoa.c
CC:  stdlib/lib_labs.c
CC:  stdlib/lib_llabs.c
CC:  stdlib/lib_bsearch.c
CC:  stdlib/lib_rand.c
CC:  stdlib/lib_qsort.c
CC:  stdlib/lib_srand.c
CC:  stdlib/lib_strtol.c
CC:  stdlib/lib_strtoll.c
CC:  stdlib/lib_strtoul.c
CC:  stdlib/lib_strtoull.c
CC:  stdlib/lib_strtod.c
CC:  stdlib/lib_strtof.c
CC:  stdlib/lib_strtold.c
CC:  stdlib/lib_checkbase.c
CC:  string/lib_ffs.c
CC:  string/lib_ffsl.c
CC:  string/lib_ffsll.c
CC:  string/lib_fls.c
CC:  string/lib_flsl.c
CC:  string/lib_flsll.c
CC:  string/lib_isbasedigit.c
CC:  string/lib_memset.c
CC:  string/lib_memchr.c
CC:  string/lib_memccpy.c
CC:  string/lib_memcmp.c
CC:  string/lib_memmove.c
CC:  string/lib_skipspace.c
CC:  string/lib_stpcpy.c
CC:  string/lib_strcasecmp.c
CC:  string/lib_strcat.c
CC:  string/lib_strchr.c
CC:  string/lib_strcpy.c
CC:  string/lib_strcmp.c
CC:  string/lib_strcspn.c
CC:  string/lib_strdup.c
CC:  string/lib_strerror.c
CC:  string/lib_strlen.c
CC:  string/lib_strnlen.c
CC:  string/lib_strncasecmp.c
CC:  string/lib_strncat.c
CC:  string/lib_strncmp.c
CC:  string/lib_strncpy.c
CC:  string/lib_strndup.c
CC:  string/lib_strcasestr.c
CC:  string/lib_strpbrk.c
CC:  string/lib_strrchr.c
CC:  string/lib_strspn.c
CC:  string/lib_strstr.c
CC:  string/lib_strtok.c
CC:  string/lib_strtokr.c
CC:  string/lib_strerrorr.c
CC:  string/lib_explicit_bzero.c
CC:  string/lib_memcpy.c
CC:  symtab/symtab_findbyname.c
CC:  symtab/symtab_findbyvalue.c
CC:  symtab/symtab_findorderedbyname.c
CC:  symtab/symtab_findorderedbyvalue.c
CC:  syslog/lib_syslog.c
CC:  syslog/lib_setlogmask.c
CC:  termios/lib_cfgetspeed.c
CC:  termios/lib_cfsetspeed.c
CC:  termios/lib_isatty.c
CC:  termios/lib_tcflush.c
CC:  termios/lib_tcgetattr.c
CC:  termios/lib_tcsetattr.c
CC:  time/lib_strftime.c
CC:  time/lib_calendar2utc.c
CC:  time/lib_daysbeforemonth.c
CC:  time/lib_gettimeofday.c
CC:  time/lib_isleapyear.c
CC:  time/lib_settimeofday.c
CC:  time/lib_time.c
CC:  time/lib_difftime.c
CC:  time/lib_mktime.c
CC:  time/lib_gmtime.c
CC:  time/lib_gmtimer.c
CC:  unistd/lib_access.c
CC:  unistd/lib_swab.c
CC:  unistd/lib_getopt.c
CC:  unistd/lib_getoptargp.c
CC:  unistd/lib_getoptindp.c
CC:  unistd/lib_getoptoptp.c
AR:    bin/lib_readdirr.o  bin/lib_telldir.o  bin/lib_fixedmath.o  bin/lib_b16sin.o  bin/lib_b16cos.o  bin/lib_b16atan2.o  bin/lib_ubsqrt.o  bin/lib_imaxabs.o  bin/lib_strtoimax.o  bin/lib_strtoumax.o  bin/lib_basename.o  bin/lib_dirname.o  bin/lib_stream.o  bin/lib_utsname.o  bin/lib_xorshift128.o  bin/lib_tea_encrypt.o  bin/lib_tea_decrypt.o  bin/lib_umul32.o  bin/lib_umul64.o  bin/lib_umul32x64.o  bin/lib_uadd32x64.o  bin/lib_uadd64.o  bin/lib_usub64x32.o  bin/lib_usub64.o  bin/lib_sendfile.o  bin/lib_streamsem.o  bin/lib_crc64.o  bin/lib_crc32.o  bin/lib_crc16.o  bin/lib_crc8.o  bin/lib_dumpbuffer.o  bin/lib_match.o  bin/lib_addrconfig.o  bin/lib_etherntoa.o  bin/lib_htons.o  bin/lib_htonl.o  bin/lib_inetaddr.o  bin/lib_inetntoa.o  bin/lib_inetntop.o  bin/lib_inetpton.o  bin/sq_addlast.o  bin/sq_addfirst.o  bin/sq_addafter.o  bin/sq_cat.o  bin/sq_rem.o  bin/sq_remlast.o  bin/sq_remfirst.o  bin/sq_remafter.o  bin/sq_count.o  bin/dq_addlast.o  bin/dq_addfirst.o  bin/dq_addafter.o  bin/dq_addbefore.o  bin/dq_cat.o  bin/dq_rem.o  bin/dq_remlast.o  bin/dq_remfirst.o  bin/dq_count.o  bin/sched_getprioritymax.o  bin/sched_getprioritymin.o  bin/task_setcanceltype.o  bin/task_testcancel.o  bin/sem_init.o  bin/sem_getprotocol.o  bin/sem_getvalue.o  bin/sem_setprotocol.o  bin/lib_psfa_addaction.o  bin/lib_psfa_addclose.o  bin/lib_psfa_adddup2.o  bin/lib_psfa_addopen.o  bin/lib_psfa_destroy.o  bin/lib_psfa_init.o  bin/lib_psa_getflags.o  bin/lib_psa_getschedparam.o  bin/lib_psa_getschedpolicy.o  bin/lib_psa_init.o  bin/lib_psa_setflags.o  bin/lib_psa_setschedparam.o  bin/lib_psa_setschedpolicy.o  bin/lib_psa_getstacksize.o  bin/lib_psa_setstacksize.o  bin/lib_fileno.o  bin/lib_printf.o  bin/lib_sprintf.o  bin/lib_asprintf.o  bin/lib_snprintf.o  bin/lib_libsprintf.o  bin/lib_vsprintf.o  bin/lib_vasprintf.o  bin/lib_vsnprintf.o  bin/lib_libvsprintf.o  bin/lib_dprintf.o  bin/lib_vdprintf.o  bin/lib_meminstream.o  bin/lib_memoutstream.o  bin/lib_memsistream.o  bin/lib_memsostream.o  bin/lib_lowoutstream.o  bin/lib_zeroinstream.o  bin/lib_nullinstream.o  bin/lib_nulloutstream.o  bin/lib_sscanf.o  bin/lib_rawinstream.o  bin/lib_rawoutstream.o  bin/lib_rawsistream.o  bin/lib_rawsostream.o  bin/lib_libnoflush.o  bin/lib_libsnoflush.o  bin/lib_remove.o  bin/lib_fopen.o  bin/lib_freopen.o  bin/lib_fclose.o  bin/lib_fread.o  bin/lib_libfread.o  bin/lib_fseek.o  bin/lib_ftell.o  bin/lib_fsetpos.o  bin/lib_fgetpos.o  bin/lib_fgetc.o  bin/lib_fgets.o  bin/lib_gets_s.o  bin/lib_gets.o  bin/lib_libfgets.o  bin/lib_fwrite.o  bin/lib_libfwrite.o  bin/lib_fflush.o  bin/lib_libflushall.o  bin/lib_libfflush.o  bin/lib_rdflush.o  bin/lib_wrflush.o  bin/lib_fputc.o  bin/lib_puts.o  bin/lib_fputs.o  bin/lib_ungetc.o  bin/lib_vprintf.o  bin/lib_fprintf.o  bin/lib_vfprintf.o  bin/lib_stdinstream.o  bin/lib_stdoutstream.o  bin/lib_stdsistream.o  bin/lib_stdsostream.o  bin/lib_perror.o  bin/lib_feof.o  bin/lib_ferror.o  bin/lib_clearerr.o  bin/lib_abs.o  bin/lib_abort.o  bin/lib_div.o  bin/lib_ldiv.o  bin/lib_lldiv.o  bin/lib_itoa.o  bin/lib_labs.o  bin/lib_llabs.o  bin/lib_bsearch.o  bin/lib_rand.o  bin/lib_qsort.o  bin/lib_srand.o  bin/lib_strtol.o  bin/lib_strtoll.o  bin/lib_strtoul.o  bin/lib_strtoull.o  bin/lib_strtod.o  bin/lib_strtof.o  bin/lib_strtold.o  bin/lib_checkbase.o  bin/lib_ffs.o  bin/lib_ffsl.o  bin/lib_ffsll.o  bin/lib_fls.o  bin/lib_flsl.o  bin/lib_flsll.o  bin/lib_isbasedigit.o  bin/lib_memset.o  bin/lib_memchr.o  bin/lib_memccpy.o  bin/lib_memcmp.o  bin/lib_memmove.o  bin/lib_skipspace.o  bin/lib_stpcpy.o  bin/lib_strcasecmp.o  bin/lib_strcat.o  bin/lib_strchr.o  bin/lib_strcpy.o  bin/lib_strcmp.o  bin/lib_strcspn.o  bin/lib_strdup.o  bin/lib_strerror.o  bin/lib_strlen.o  bin/lib_strnlen.o  bin/lib_strncasecmp.o  bin/lib_strncat.o  bin/lib_strncmp.o  bin/lib_strncpy.o  bin/lib_strndup.o  bin/lib_strcasestr.o  bin/lib_strpbrk.o  bin/lib_strrchr.o  bin/lib_strspn.o  bin/lib_strstr.o  bin/lib_strtok.o  bin/lib_strtokr.o  bin/lib_strerrorr.o  bin/lib_explicit_bzero.o  bin/lib_memcpy.o  bin/symtab_findbyname.o  bin/symtab_findbyvalue.o  bin/symtab_findorderedbyname.o  bin/symtab_findorderedbyvalue.o  bin/lib_syslog.o  bin/lib_setlogmask.o  bin/lib_cfgetspeed.o  bin/lib_cfsetspeed.o  bin/lib_isatty.o  bin/lib_tcflush.o  bin/lib_tcgetattr.o  bin/lib_tcsetattr.o  bin/lib_strftime.o  bin/lib_calendar2utc.o  bin/lib_daysbeforemonth.o  bin/lib_gettimeofday.o  bin/lib_isleapyear.o  bin/lib_settimeofday.o  bin/lib_time.o  bin/lib_difftime.o  bin/lib_mktime.o  bin/lib_gmtime.o  bin/lib_gmtimer.o  bin/lib_access.o  bin/lib_swab.o  bin/lib_getopt.o  bin/lib_getoptargp.o  bin/lib_getoptindp.o  bin/lib_getoptoptp.o
make[1]: Leaving directory '/home/alan/nuttx-project/libc'
make[1]: Entering directory '/home/alan/nuttx-project/mm'
CC:  mm_heap/mm_initialize.c
CC:  mm_heap/mm_sem.c
CC:  mm_heap/mm_addfreechunk.c
CC:  mm_heap/mm_size2ndx.c
CC:  mm_heap/mm_shrinkchunk.c
CC:  mm_heap/mm_brkaddr.c
CC:  mm_heap/mm_calloc.c
CC:  mm_heap/mm_extend.c
CC:  mm_heap/mm_free.c
CC:  mm_heap/mm_mallinfo.c
CC:  mm_heap/mm_malloc.c
CC:  mm_heap/mm_memalign.c
CC:  mm_heap/mm_realloc.c
CC:  mm_heap/mm_zalloc.c
CC:  umm_heap/umm_initialize.c
CC:  umm_heap/umm_addregion.c
CC:  umm_heap/umm_sem.c
CC:  umm_heap/umm_brkaddr.c
CC:  umm_heap/umm_calloc.c
CC:  umm_heap/umm_extend.c
CC:  umm_heap/umm_free.c
CC:  umm_heap/umm_mallinfo.c
CC:  umm_heap/umm_malloc.c
CC:  umm_heap/umm_memalign.c
CC:  umm_heap/umm_realloc.c
CC:  umm_heap/umm_zalloc.c
CC:  umm_heap/umm_globals.c
AR:    bin/mm_initialize.o  bin/mm_sem.o  bin/mm_addfreechunk.o  bin/mm_size2ndx.o  bin/mm_shrinkchunk.o  bin/mm_brkaddr.o  bin/mm_calloc.o  bin/mm_extend.o  bin/mm_free.o  bin/mm_mallinfo.o  bin/mm_malloc.o  bin/mm_memalign.o  bin/mm_realloc.o  bin/mm_zalloc.o  bin/umm_initialize.o  bin/umm_addregion.o  bin/umm_sem.o  bin/umm_brkaddr.o  bin/umm_calloc.o  bin/umm_extend.o  bin/umm_free.o  bin/umm_mallinfo.o  bin/umm_malloc.o  bin/umm_memalign.o  bin/umm_realloc.o  bin/umm_zalloc.o  bin/umm_globals.o
make[1]: Leaving directory '/home/alan/nuttx-project/mm'
make[1]: Entering directory '/home/alan/nuttx-project/arch/arm/src'
AS:  chip/gnu/stm32_vectors.S
AS:  armv7-m/gnu/up_saveusercontext.S
AS:  armv7-m/gnu/up_fullcontextrestore.S
AS:  armv7-m/gnu/up_switchcontext.S
AS:  armv7-m/gnu/up_testset.S
AS:  armv7-m/gnu/vfork.S
AS:  armv7-m/gnu/up_exception.S
CC:  chip/stm32_allocateheap.c
CC:  chip/stm32_start.c
CC:  chip/stm32_rcc.c
CC:  chip/stm32_lse.c
CC:  chip/stm32_lsi.c
CC:  chip/stm32_gpio.c
CC:  chip/stm32_exti_gpio.c
CC:  chip/stm32_flash.c
CC:  chip/stm32_irq.c
CC:  chip/stm32_dma.c
CC:  chip/stm32_lowputc.c
CC:  chip/stm32_serial.c
CC:  chip/stm32_spi.c
CC:  chip/stm32_i2s.c
CC:  chip/stm32_sdio.c
CC:  chip/stm32_tim.c
CC:  chip/stm32_waste.c
CC:  chip/stm32_ccm.c
CC:  chip/stm32_uid.c
CC:  chip/stm32_capture.c
CC:  chip/stm32_timerisr.c
CC:  chip/stm32_i2c.c
CC:  chip/stm32_idle.c
CC:  chip/stm32_pmstop.c
CC:  chip/stm32_pmstandby.c
CC:  chip/stm32_pmsleep.c
CC:  chip/stm32_pminitialize.c
CC:  armv7-m/up_assert.c
CC:  armv7-m/up_blocktask.c
CC:  armv7-m/up_copyfullstate.c
CC:  common/up_createstack.c
CC:  common/up_mdelay.c
CC:  common/up_udelay.c
CC:  common/up_exit.c
CC:  common/up_initialize.c
CC:  armv7-m/up_initialstate.c
CC:  common/up_interruptcontext.c
CC:  armv7-m/up_memfault.c
CC:  common/up_modifyreg8.c
CC:  common/up_modifyreg16.c
CC:  common/up_modifyreg32.c
CC:  armv7-m/up_releasepending.c
CC:  common/up_releasestack.c
CC:  armv7-m/up_reprioritizertr.c
CC:  armv7-m/up_schedulesigaction.c
CC:  armv7-m/up_sigdeliver.c
CC:  common/up_stackframe.c
CC:  armv7-m/up_systemreset.c
CC:  armv7-m/up_unblocktask.c
CC:  common/up_usestack.c
CC:  armv7-m/up_doirq.c
CC:  armv7-m/up_hardfault.c
CC:  armv7-m/up_svcall.c
CC:  common/up_vfork.c
CC:  armv7-m/up_vectors.c
AR:  stm32_vectors.o up_saveusercontext.o up_fullcontextrestore.o up_switchcontext.o up_testset.o vfork.o up_exception.o stm32_allocateheap.o stm32_start.o stm32_rcc.o stm32_lse.o stm32_lsi.o stm32_gpio.o stm32_exti_gpio.o stm32_flash.o stm32_irq.o stm32_dma.o stm32_lowputc.o stm32_serial.o stm32_spi.o stm32_i2s.o stm32_sdio.o stm32_tim.o stm32_waste.o stm32_ccm.o stm32_uid.o stm32_capture.o stm32_timerisr.o stm32_i2c.o stm32_idle.o stm32_pmstop.o stm32_pmstandby.o stm32_pmsleep.o stm32_pminitialize.o up_assert.o up_blocktask.o up_copyfullstate.o up_createstack.o up_mdelay.o up_udelay.o up_exit.o up_initialize.o up_initialstate.o up_interruptcontext.o up_memfault.o up_modifyreg8.o up_modifyreg16.o up_modifyreg32.o up_releasepending.o up_releasestack.o up_reprioritizertr.o up_schedulesigaction.o up_sigdeliver.o up_stackframe.o up_systemreset.o up_unblocktask.o up_usestack.o up_doirq.o up_hardfault.o up_svcall.o up_vfork.o up_vectors.o
make[1]: Leaving directory '/home/alan/nuttx-project/arch/arm/src'
make[1]: Entering directory '/home/alan/apps'
make[2]: Entering directory '/home/alan/apps/examples/hello'
CC:  hello_main.c
AR:     hello_main.o
make[2]: Leaving directory '/home/alan/apps/examples/hello'
make[2]: Entering directory '/home/alan/apps/examples/nsh'
CC:  nsh_main.c
AR:     nsh_main.o
make[2]: Leaving directory '/home/alan/apps/examples/nsh'
make[2]: Entering directory '/home/alan/apps/nshlib'
CC:  nsh_init.c
CC:  nsh_parse.c
CC:  nsh_console.c
CC:  nsh_script.c
CC:  nsh_system.c
CC:  nsh_command.c
CC:  nsh_fscmds.c
CC:  nsh_ddcmd.c
CC:  nsh_proccmds.c
CC:  nsh_mmcmds.c
CC:  nsh_timcmds.c
CC:  nsh_envcmds.c
CC:  nsh_syscmds.c
CC:  nsh_dbgcmds.c
CC:  nsh_session.c
CC:  nsh_fsutils.c
CC:  nsh_consolemain.c
AR:   nsh_init.o nsh_parse.o nsh_console.o nsh_script.o nsh_system.o nsh_command.o nsh_fscmds.o nsh_ddcmd.o nsh_proccmds.o nsh_mmcmds.o nsh_timcmds.o nsh_envcmds.o nsh_syscmds.o nsh_dbgcmds.o nsh_session.o nsh_fsutils.o nsh_consolemain.o
make[2]: Leaving directory '/home/alan/apps/nshlib'
make[2]: Entering directory '/home/alan/apps/system/readline'
CC:  readline.c
CC:  readline_common.c
AR:   readline.o readline_common.o
make[2]: Leaving directory '/home/alan/apps/system/readline'
make[2]: Entering directory '/home/alan/apps/platform'
AR:   
make[2]: Leaving directory '/home/alan/apps/platform'
make[1]: Leaving directory '/home/alan/apps'
make[1]: Entering directory '/home/alan/nuttx-project/fs'
CC:  fs_initialize.c
CC:  inode/fs_files.c
CC:  inode/fs_foreachinode.c
CC:  inode/fs_inode.c
CC:  inode/fs_inodeaddref.c
CC:  inode/fs_inodebasename.c
CC:  inode/fs_inodefind.c
CC:  inode/fs_inodefree.c
CC:  inode/fs_inoderelease.c
CC:  inode/fs_inoderemove.c
CC:  inode/fs_inodereserve.c
CC:  inode/fs_inodesearch.c
CC:  inode/fs_filedetach.c
CC:  vfs/fs_close.c
CC:  vfs/fs_dup.c
CC:  vfs/fs_dup2.c
CC:  vfs/fs_fcntl.c
CC:  vfs/fs_dupfd.c
CC:  vfs/fs_dupfd2.c
CC:  vfs/fs_epoll.c
CC:  vfs/fs_fstat.c
CC:  vfs/fs_fstatfs.c
CC:  vfs/fs_getfilep.c
CC:  vfs/fs_ioctl.c
CC:  vfs/fs_lseek.c
CC:  vfs/fs_mkdir.c
CC:  vfs/fs_open.c
CC:  vfs/fs_poll.c
CC:  vfs/fs_read.c
CC:  vfs/fs_rename.c
CC:  vfs/fs_rmdir.c
CC:  vfs/fs_statfs.c
CC:  vfs/fs_stat.c
CC:  vfs/fs_select.c
CC:  vfs/fs_unlink.c
CC:  vfs/fs_write.c
CC:  vfs/fs_pread.c
CC:  vfs/fs_pwrite.c
CC:  vfs/fs_link.c
CC:  vfs/fs_readlink.c
CC:  vfs/fs_fdopen.c
CC:  driver/fs_registerdriver.c
CC:  driver/fs_unregisterdriver.c
CC:  dirent/fs_closedir.c
CC:  dirent/fs_opendir.c
CC:  dirent/fs_readdir.c
CC:  dirent/fs_rewinddir.c
CC:  dirent/fs_seekdir.c
CC:  mmap/fs_mmap.c
AR:   fs_initialize.o fs_files.o fs_foreachinode.o fs_inode.o fs_inodeaddref.o fs_inodebasename.o fs_inodefind.o fs_inodefree.o fs_inoderelease.o fs_inoderemove.o fs_inodereserve.o fs_inodesearch.o fs_filedetach.o fs_close.o fs_dup.o fs_dup2.o fs_fcntl.o fs_dupfd.o fs_dupfd2.o fs_epoll.o fs_fstat.o fs_fstatfs.o fs_getfilep.o fs_ioctl.o fs_lseek.o fs_mkdir.o fs_open.o fs_poll.o fs_read.o fs_rename.o fs_rmdir.o fs_statfs.o fs_stat.o fs_select.o fs_unlink.o fs_write.o fs_pread.o fs_pwrite.o fs_link.o fs_readlink.o fs_fdopen.o fs_registerdriver.o fs_unregisterdriver.o fs_closedir.o fs_opendir.o fs_readdir.o fs_rewinddir.o fs_seekdir.o fs_mmap.o
make[1]: Leaving directory '/home/alan/nuttx-project/fs'
make[1]: Entering directory '/home/alan/nuttx-project/binfmt'
CC:  binfmt_globals.c
CC:  binfmt_register.c
CC:  binfmt_unregister.c
CC:  binfmt_loadmodule.c
CC:  binfmt_unloadmodule.c
CC:  binfmt_execmodule.c
CC:  binfmt_exec.c
CC:  binfmt_copyargv.c
CC:  binfmt_dumpmodule.c
AR:   binfmt_globals.o binfmt_register.o binfmt_unregister.o binfmt_loadmodule.o binfmt_unloadmodule.o binfmt_execmodule.o binfmt_exec.o binfmt_copyargv.o binfmt_dumpmodule.o
make[1]: Leaving directory '/home/alan/nuttx-project/binfmt'
make[1]: Entering directory '/home/alan/nuttx-project/arch/arm/src'
make[2]: Entering directory '/home/alan/nuttx-project/configs/stm32f103-minimum/src'
CC:  stm32_boot.c
CC:  stm32_bringup.c
CC:  stm32_spi.c
CC:  stm32_userleds.c
AR:   stm32_boot.o stm32_bringup.o stm32_spi.o stm32_userleds.o 
make[2]: Leaving directory '/home/alan/nuttx-project/configs/stm32f103-minimum/src'
LD: nuttx
make[1]: Leaving directory '/home/alan/nuttx-project/arch/arm/src'
CP: nuttx.bin

Now let see the NuttX’s “hello world” size:

$ arm-none-eabi-size nuttx
   text	   data	    bss	    dec	    hex	filename
  15068	     84	   1676	  16828	   41bc	nuttx

So, the NuttX’s helloworld is about 15KB.

Time to compile and compare Zephyr:

$ git clone https://gerrit.zephyrproject.org/r/zephyr zephyr-project
$ cd zephyr-project/
$ git checkout tags/v1.6.0
$ export ZEPHYR_BASE=/home/alan/zephyr-project
$ export ZEPHYR_GCC_VARIANT=gccarmemb
$ export GCCARMEMB_TOOLCHAIN_PATH=/usr
$ cd samples/hello_world/
$ make BOARD=frdm_k64f
make[1]: Entering directory '/home/alan/zephyr/zephyr-project'
make[2]: Entering directory '/home/alan/zephyr/zephyr-project/samples/hello_world/outdir/frdm_k64f'
  GEN     ./Makefile
scripts/kconfig/conf --silentoldconfig Kconfig
  Using /home/alan/zephyr/zephyr-project as source for kernel
  GEN     ./Makefile
  CHK     include/generated/version.h
  UPD     include/generated/version.h
  CHK     misc/generated/configs.c
  UPD     misc/generated/configs.c
  CHK     include/generated/offsets.h
  UPD     include/generated/offsets.h
  CHK     misc/generated/sysgen/prj.mdef
  UPD     misc/generated/sysgen/prj.mdef
  LD      lib/iot/built-in.o
  LD      lib/libc/minimal/source/stdlib/built-in.o
  CC      lib/libc/minimal/source/stdout/fprintf.o
  CC      lib/libc/minimal/source/stdout/prf.o
  CC      lib/libc/minimal/source/stdout/sprintf.o
  CC      lib/libc/minimal/source/stdout/stdout_console.o
  LD      lib/libc/minimal/source/stdout/built-in.o
  CC      lib/libc/minimal/source/string/string.o
  LD      lib/libc/minimal/source/string/built-in.o
  LD      lib/libc/minimal/source/built-in.o
  LD      lib/libc/minimal/built-in.o
  LD      lib/libc/built-in.o
  LD      lib/built-in.o
  CC      misc/printk.o
  LD      misc/debug/built-in.o
  CC      misc/generated/configs.o
  CC      misc/generated/sysgen/kernel_main.o
  LD      misc/generated/sysgen/built-in.o
  LD      misc/generated/built-in.o
  LD      misc/built-in.o
  LD      net/built-in.o
  LD      boards/arm/frdm_k64f/built-in.o
  LD      boards/built-in.o
  LD      ext/fs/built-in.o
  CC      ext/hal/ksdk/devices/MK64F12/fsl_clock.o
  LD      ext/hal/ksdk/components/built-in.o
  LD      ext/hal/ksdk/drivers/built-in.o
  LD      ext/hal/ksdk/built-in.o
  LD      ext/hal/built-in.o
  LD      ext/lib/crypto/built-in.o
  LD      ext/lib/built-in.o
  LD      ext/built-in.o
  LD      subsys/built-in.o
  LD      tests/built-in.o
  AS      arch/arm/core/exc_exit.o
  CC      arch/arm/core/irq_init.o
  AS      arch/arm/core/swap.o
  CC      arch/arm/core/fault.o
  CC      arch/arm/core/irq_manage.o
  CC      arch/arm/core/thread.o
  AS      arch/arm/core/cpu_idle.o
  AS      arch/arm/core/fault_s.o
  AS      arch/arm/core/isr_wrapper.o
  CC      arch/arm/core/fatal.o
  CC      arch/arm/core/sys_fatal_error_handler.o
  CC      arch/arm/core/thread_abort.o
  AS      arch/arm/core/cortex_m/vector_table.o
  AS      arch/arm/core/cortex_m/reset.o
  AS      arch/arm/core/cortex_m/nmi_on_reset.o
  CC      arch/arm/core/cortex_m/prep_c.o
  CC      arch/arm/core/cortex_m/scs.o
  CC      arch/arm/core/cortex_m/scb.o
  CC      arch/arm/core/cortex_m/nmi.o
  CC      arch/arm/core/cortex_m/exc_manage.o
  CC      arch/arm/core/cortex_m/irq_vector_table.o
  AS      arch/arm/core/cortex_m/sw_isr_table.o
  LD      arch/arm/core/cortex_m/built-in.o
  LD      arch/arm/core/built-in.o
  CC      arch/arm/soc/nxp_kinetis/k6x/soc_config.o
  CC      arch/arm/soc/nxp_kinetis/k6x/soc.o
  AS      arch/arm/soc/nxp_kinetis/k6x/wdog.o
  LD      arch/arm/soc/nxp_kinetis/k6x/built-in.o
  LD      arch/arm/soc/nxp_kinetis/built-in.o
  LD      arch/arm/built-in.o
  LD      arch/built-in.o
  CC      drivers/console/uart_console.o
  LD      drivers/console/built-in.o
  CC      drivers/gpio/gpio_k64.o
  LD      drivers/gpio/built-in.o
  LD      drivers/interrupt_controller/built-in.o
  CC      drivers/pinmux/k64/pinmux.o
  CC      drivers/pinmux/k64/pinmux_board_frdm_k64f.o
  LD      drivers/pinmux/built-in.o
  LD      drivers/random/built-in.o
  CC      drivers/serial/uart_k20.o
  LD      drivers/serial/built-in.o
  CC      drivers/timer/cortex_m_systick.o
  CC      drivers/timer/sys_clock_init.o
  LD      drivers/timer/built-in.o
  LD      drivers/built-in.o
  CC      kernel/unified/version.o
  LD      kernel/unified/built-in.o
  CC      kernel/unified/alert.o
  CC      kernel/unified/device.o
  CC      kernel/unified/errno.o
  CC      kernel/unified/fifo.o
  CC      kernel/unified/idle.o
  CC      kernel/unified/init.o
  CC      kernel/unified/legacy_offload.o
  CC      kernel/unified/legacy_timer.o
  CC      kernel/unified/lifo.o
  CC      kernel/unified/mailbox.o
  CC      kernel/unified/mem_pool.o
  CC      kernel/unified/mem_slab.o
  CC      kernel/unified/msg_q.o
  CC      kernel/unified/mutex.o
  CC      kernel/unified/pipes.o
  CC      kernel/unified/sched.o
  CC      kernel/unified/sem.o
  CC      kernel/unified/stack.o
  CC      kernel/unified/sys_clock.o
  CC      kernel/unified/system_work_q.o
  CC      kernel/unified/thread.o
  CC      kernel/unified/thread_abort.o
  CC      kernel/unified/timer.o
  CC      kernel/unified/work_q.o
  AR      kernel/unified/lib.a
  CC      src/main.o
  LD      src/built-in.o
  AR      libzephyr.a
  LINK    zephyr.lnk
  BIN     zephyr.bin
make[2]: Leaving directory '/home/alan/zephyr/zephyr-project/samples/hello_world/outdir/frdm_k64f'
make[1]: Leaving directory '/home/alan/zephyr/zephyr-project'

And the size is:

$ arm-none-eabi-size outdir/frdm_k64f/zephyr.elf 
   text	   data	    bss	    dec	    hex	filename
  10226	    400	   7808	  18434	   4802	outdir/frdm_k64f/zephyr.elf

Then Zephyr’s size is about 10KB!

Maybe you could think: “Oh, NuttX is 50% bigger!”, but you are wrong here.

First: NuttX is a real POSIX RTOS, the helloworld example use the POSIX printf() function. Zephyr is not POSIX and it uses a limited/trimmed-down printk() function.

Second: as you saw NuttX compiled many more files and this simple helloworld includes File System support and the structure to support Device Drivers.

Third: this 15KB is only the initial overhead, probably NuttX increases more slowly than Zephyr because NuttX is very modular and its features are separated in many files.