undefined reference to _open when using libc with NCS 2.4.2 and above

[pnc2]

Hello,

I am developing an application for a custom nrf52840 board. This application has been building and running without problems for nrf Connect SDK v 2.3.0

However, I recently tried to upgrade to NCS v2.5.0 and I get the below link-time error:

D:/ncs2/toolchains/c57af46cb7/opt/zephyr-sdk/arm-zephyr-eabi/arm-zephyr-eabi/lib/thumb/v7e-m/nofp\libc.a(lib_a-openr.o): in function `_open_r':
openr.c:(.text._open_r+0x14): undefined reference to `_open'

Note that 

CONFIG_NEWLIB_LIBC=y

CONFIG_FILE_SYSTEM=y

CONFIG_FILE_SYSTEM_LITTLEFS=y

is set in my prj.conf. I also see these lines in autoconf.h: 

#define CONFIG_FULL_LIBC_SUPPORTED 1
#define CONFIG_MINIMAL_LIBC_SUPPORTED 1
#define CONFIG_NEWLIB_LIBC_SUPPORTED 1
#define CONFIG_PICOLIBC_SUPPORTED 1
#define CONFIG_NEWLIB_LIBC 1
#define CONFIG_HAS_NEWLIB_LIBC_NANO 1

I tried to downgrade to NCS 2.4.2, but it seems to have the same issue. However, no problems with NCS v2.3.0

Has something changed since NCS 2.4.2? Am I supposed to enable some other config flag as well, in order to use full newlib libc?

thanks

regards

pnc

[pnc2]

By the way, I have also now tried it with NCS2.5.99-dev1, and the problem is still there.

[Håkon Alseth]

Hi,

 

fopen() is a std lib function that is provided by the libc that is chosen, and for newlib (and newlib-nano), this is provided by the toolchain that you use.

I would recommend that you use the zephyr fs subsys.

 

Kind regards,

Håkon

[pnc2]

Hi Hakon,

as you will see from the above messages, I already have 

CONFIG_FILE_SYSTEM=y

I use the posix file API for a particular reason (as I mentioned in my first message) It is a project requirement. Also, as previously mentioned, my code works fine with NCS 2.3.0 and below. Something seems to have broken with NCS 2.5.0. As for toolchain, I use the toolchain that your Toolchain Manager installs along with NCS 2.5.0

I have also mentioned above that I have reproduced this problem above with a Nordic board and a standard sample. I request you to please look into this.

Thanks

[Håkon Alseth]

Hi,

 

The POSIX support in zephyr is partial for DEVICE_IO, as shown here:

https://docs.zephyrproject.org/latest/services/portability/posix/option_groups/index.html#posix-device-io

When adding CONFIG_POSIX_FS=y, I see that this compiles in ncs v2.3.0 (zephyr v3.2.99-ncs1) and fails to compile in ncs v2.5.0.

If we fallback to picolib (CONFIG_PICOLIB=y), the default selected libc in zephyr, it does compile as expected.

 

I would recommend that you open a issue on zephyr github wrt. POSIX compatibility:

https://github.com/zephyrproject-rtos/zephyr/issues

 

Kind regards,

Håkon

[pnc2]

Hi Hakon,

as suggested by you, I posted this to Zephyr issues forum. Here is the link:

https://github.com/zephyrproject-rtos/zephyr/issues/66132

This was the "helpful" response I got:

====================================================

Thank you for reporting this. However - unless you are able to reproduce this issue with upstream Zephyr main - please report issues with the nRF Connect SDK (NCS) on the Nordic Semiconductor DevZone.

==================================================

As mentioned previously, I already have tried it out with the latest development version of NCS 2.5.99-dev1 ( Zephyr 3.4.99). Unfortunately, you do not use upstream Zephyr, but a fork of Zephyr currently at 3.4.99, and it is clear that the Zephyr folk won't help me unless I can reproduce this with upstream Zephyr main (currently at 3.5.99).

As my organization's hardware vendor, it is certainly your responsibility to fix this issue, rather than batting this down to Zephyr.