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From: Julio Di Egidio <julio@diegidio.name>
Newsgroups: comp.lang.c
Subject: Re: So You Think You Can Const?
Date: Sat, 11 Jan 2025 17:21:25 +0100
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On 11/01/2025 17:07, Julio Di Egidio wrote:
> On 11/01/2025 12:14, David Brown wrote:
>> On 10/01/2025 19:56, Keith Thompson wrote:
> <snip>
>> The idea was to place the emphasis on "free" changing the pointer, 
>> rather than the data pointed to.
> 
> I feel I am still altogether missing the point.
> 
> Is my understanding correct that when freeing a pointer: 1) the pointer 
> value, i.e. the address it holds, does not change; OTOH, 2) the 
> pointed-to object does change, in the sense that it is marked unusable 
> (and, supposedly, made available to re-allocation)?
> 
> Moreover, while the pointer value has not changed, it is in fact changed 
> in the sense that it has become invalid, namely the pointer cannot be 
> used (validly dereferenced) anymore.  Not just that, but *every* pointer 
> to the same object, i.e. holding the same address, has become invalid.
> 
> All that considered, how isn't `void free(void *p)`, i.e. with no const 
> qualifiers anywhere, the only reasonable signature?

In fact, along that line, I could see one might insist that "strictly 
speaking, it should be `void free(void *const p)` because the pointer 
value is not changed" (my considerations above are indeed more 
"semantic"), OTOH, I just cannot see a case for `void free(void const 
*p)`, not even strictly technically.

-Julio