Add strcspn and iscntrl to minimal libc

[tgorochowik]

This PR adds the definitions for strcspn and iscntrl to the minimal libc library (strings).

[zephyrbot]

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[pfalcon]

These should have "libc: minimal: add ..." titles, otherwise look good, thanks for improving minlibc.

[nashif]

I am reopening a branch I started working on last year to import a more complete base libc to replace minimal libc which includes all those functions you are adding.

Lets put this on hold, you can add those function to the sample for now while we try to get a more complete c library.

[pfalcon]

now while we try to get a more complete c library.

We already have "a more complete c library", it's called Newlib. What we need is to elaborate minimal libc, while keeping it minimal by the code size. Anyway, let's what that "more complete base libc" might be...

[nashif]

a more complete c library

more complete than the minimal libc but still minimal and basic that is part of the Zephyr project. So we agree.

Not everyone wants or needs newlib.

[andrewboie]

Has anyone looked into nano-newlib as a replacement for minimal libc?
Really we need to get out of the C library business...I would prefer we just moved to third-party C libraries we can add to the west manifest and purged minimal libc from the tree completely

[nashif]

Has anyone looked into nano-newlib as a replacement for minimal libc?

that is what I am looking into now.

[KozhinovAlexander]

I am reopening a branch I started working on last year to import a more complete base libc to replace minimal libc which includes all those functions you are adding.

Lets put this on hold, you can add those function to the sample for now while we try to get a more complete c library.

@nashif

• Could you please provide the link to your active working new new libc implementation here?
• Can I also participate on meaning by you PR?