Make all sync mechanisms public

[jean-roland]

Some system-abstracted functions where public, like z_time and z_clock while the multi-thread ones z_task, z_mutex and z_condvar were not. This PR fixes this inconsistency that was noted in #271.

Note that 2 systems are not fully covered (functions and types are stubs):

• Arduino/opencr has no support for task, mutex and condvar
• FreeRTOS has no support for condvar

[github-advanced-security]

Cppcheck (reported by Codacy) found more than 20 potential problems in the proposed changes. Check the Files changed tab for more details.

[p-avital]

If we want them public, can it at least be restricted to zp namespace? Otherwise zenoh-c will also have to expose these

[Mallets]

I agree with @p-avital . Let's expose them public but with the zp_ prefix.

[jean-roland]

But wasn't Zenoh C supposed to eventually or already expose at least some of these? Also it would be weird to have some of them in z_ and some in zp_ so here are all the mechanisms concerned:

• z_random
• z_malloc/z_free
• z_task
• z_mutex
• z_condvar
• z_sleep
• z_clock
• z_time

[Mallets]

But wasn't Zenoh C supposed to eventually or already expose at least some of these? Also it would be weird to have some of them in z_ and some in zp_ so here are all the mechanisms concerned:

• z_random
• z_malloc/z_free
• z_task
• z_mutex
• z_condvar
• z_sleep
• z_clock
• z_time

I think we need a table checking what is supported and what not. The real API I'm quite confident restricting to zp_ only for now is z_task since zenoh-c is a binding to async Rust. We might expose it in the future though. Comments?

[jean-roland]

Agreed for z_task, and beside z_random that is not used in the examples, exposing the others on zenoh-c should allow the zenoh-pico examples to run on zenoh-c.

[Mallets]

I believe the type should be called zp_task_t.

[Mallets]

I believe the type should be called zp_task_attr_t.

[Mallets]

It seems that z_mutex_t and z_condvar_t are not available in zenoh-c.

[Mallets]

Before merging, can you please confirm that:

z_malloc/z_free
z_mutex
z_condvar
z_sleep
z_clock
z_time

are all supported in zenoh-c?

[jean-roland]

None of these types are currently supported in zenoh-c

[Mallets]

Ok, then let's stick to zp_xxx namespace.
Once those functions are added to zenoh-c we can always do a #define zp_xxx z_xxx for backward compatibility.