Re: So You Think You Can Const?

On 10/01/2025 19:56, Keith Thompson wrote:

David Brown <david.brown@hesbynett.no> writes:
[...]

If you want a better signature for "free", then I would suggest "void
free(void ** p)" - that (to me) more naturally shows that the function
is freeing the pointer, while also greatly reducing the "use after
free" errors in C code by turning them into "dereferencing a null
pointer" errors which are more easily caught by many OS's.

 I'm not sure that would work.  A void** argument means you need to pass
a pointer to a void* object.  If you've assigned the converted result of
malloc() to, say, an int* object, you don't have a void* object.  (int*
and void* might not even have the same representation).
 

Yes, you are right - while "free(void ** p)" might often be feasible in practice (since on most implementations, pointers are the same size and representation) it would at a minimum rely on compilers being somewhat lax about accepting these conversions.  Certainly it is not something that could be part of the standard.
The idea was to place the emphasis on "free" changing the pointer, rather than the data pointed to.  But it could not be done as simply as I had suggested.

Some kind of generic function that takes a pointer to an object of any
object pointer type could work, but the language doesn't support that.
(C++ addressed this by making `new` and `delete` built-in operators
rather than library functions.)