[En-Nut-Discussion] Use of alloca in Nut/OS

[Henrik Maier]

Hi Ole,

> We just differentiate between GNU and IMAGECRAFT in the usage of alloca.
> Imagefcraft does not support alloca as well.
> 
> That's right. My intention was to speedup the code by using alloca for
> dynamic allocation of just small amounts of stack for temporaly holding
> a short string. Using NutHeapAlloc is much slower and will potentially
> fragment the heap if some other heap is allocated in the meanwhile.

I agree with those reasons and in principal stack allocation has benefits.
The challenge is to balance both requirements.

> Would be an idea. I even would vote to use it in more places, but that's
> only possible if every compiler would support alloca. Perhaps we could
> add our own alloca implementation? (By just moving the stack pointer by
> x bytes). Shure, it does not help on systems with low memory...
> Any more thoughts on it?

I suggest to leave it to the system designer (the person who configures
Nut/OS for a particular platform) to decide which way to go. That means an
entry in the Configurator rather using magic pre-processor definitions.
There are also ARM based systems out there with only 32K of RAM where the
thread stack space may only be 512 bytes.

Henrik