Find a better naming for "MAIN"-constants

[OlegHahm]

There are two constants in RIOT having a MAIN in their name, that are actually meant to be used not only for the main thread (as the name would suggest) but as standard case:

• KERNEL_CONF_STACKSIZE_MAIN
• PRIORITY_MAIN

In order to reflect the intension to use these variables as a default value I propose to add a constant PRIORITY_DEFAULT. However, for the stack size constant it's a bit more difficult, because we already have a KERNEL_CONF_STACKSIZE_DEFAULT which differs from KERNEL_CONF_STACKSIZE_MAIN by not offering enough stack for using printf(). So, in short I'm looking for a more self-explaining name for a constant set to (KERNEL_CONF_STACKSIZE_DEFAULT + KERNEL_CONF_STACKSIZE_PRINTF).

[Jentsch]

Why not increment KERNEL_CONF_STACKSIZE_PRINTF by KERNEL_CONF_STACKSIZE_DEFAULT and drop the KERNEL_CONF_STACKSIZE_MAIN name?

[OlegHahm]

Well, KERNEL_CONF_STACKSIZE_DEFAULT is the recommended stack size for a "normal" thread (not using printf). KERNEL_CONF_STACKSIZE_PRINTF is the additional stack size needed if the thread uses printf() (might be zero). Since the main thread always uses printf() KERNEL_CONF_STACKSIZE_MAIN is a sum of both. I would say, all three macros are needed.

[Jentsch]

I would think currently …STACKSIZE_PRINT has no meaning for application developer.

Either I create a thread with printf, then I use …STACKSIZE_DEFAULT or I use printf and use …STACKSIZE_MAIN, but I would never use …STACKSIZE_PRINTF. It's only confusing to have such an option. (see this discussion)

May we should keep …STACKSIZE_PRINTF for internals (e.g. calculation of …STACKSIZE_MAIN) but hide it somehow from application developers.

[OlegHahm]

What about this case: your application or library needs to spawn a thread and you know that it requires a stack either much smaller or much bigger than the default case. But this thread also calls printf() and you know that some platforms with shitty libcs (say newlibc) require additional stack for these calls.

Anyway, if I get you right you feel comfortable with KERNEL_CONF_STACKSIZE_DEFAULT and KERNEL_CONF_STACKSIZE_MAIN and are only confused about this PRINTF define?

[Jentsch]

Let me rephrase it: my application needs printf and needs much more memory than usually. KERNEL_CONF_STACKSIZE_MAIN + X where X is the additional memory. Still no need for ...STACKSIZE_PRINTF.

[OlegHahm]

It seems no one has a good idea.