Lies in education [was Re: The "loop and a half"]

[bartc]

On 13/10/2017 07:16, Gregory Ewing wrote:
> Steve D'Aprano wrote:
>> On Fri, 13 Oct 2017 03:37 pm, Gregory Ewing wrote:
>>
>>> If the compiler can tell where p is initially pointing, it could
>>> put the pointer in read-only memory.
>>
>> If it's read-only, how can the compiler write to it?
>>
>> (I come from the days when ROM was actual ROM, burned in at the factory.)
> 
> So, the factory is allowed to write to it. Possibly
> it's writing data that came from... a compiler?
> 
> A memory that couldn't be written to at all, ever, would
> be a bit useless!
> 

It's read-only in the same sense as a printed book; you can't change the 
marks already on the page.

I've programmed EPROMS. Neither the C language nor the concept of 
'const' attributes for data ever came into it. While executable code 
doesn't really need it.

It is simply not a necessity. You just arranged for writeable portions 
of memory to be at different locations than that containing the code and 
fixed data. Sometimes it was only data.

'const' is anyway the wrong sort of attribute to use, as I've already 
explained. For example:

   const int A = rand();  // inside a function

A is written to multiple times at runtime. It can't go into actual 
read-only memory like a ROM. And it might have trouble going into a 
memory page with read-only attributes.

'const' tries to do too many things, most of them poorly, although it 
does a very good job at adding clutter.

-- 
bartc