Re: Help porting newlib to a new CPU architecture (sorta)

["Hans-Bernhard Bröker" <HBBroeker@t-online.de>]

Am 06.07.2021 um 21:04 schrieb Orlando Arias:

> Right, went back and looked at the standard. There is no description of
> what the abstract machine for the execution environment should be. I
> guess my confusion came from the second paragraph in [1]. Harvard
> architectures still have the thing that you have to define whether a
> pointer refers to something in program space or data space, and standard
> C has no way of signaling this. 

You're mixing thing up there.  Standard C has a perfectly fine 
distinction between program space and data space, including pointers 
thereto.  Function pointers and data pointers _are_ distinct.

What Standard C does lack is a standardized distinction between pointers 
into ROM data and RAM data.  const-qualified pointers may seem like they 
offer that, but ultimately they don't.

> This is what I meant by the von Neumann requirement: all pointers
> dereference to the same address space. 

That's stated broadly enough to be wrong.  The C virtual machine is, in 
fact, a Harvard architecture.  It assumes that const and non-const data 
live in the same address space, but that doesn't make it von-Neumann.