Re: [Sdcc-user] _Optional

[Maarten B. <sou...@ds...>]

Philipp Klaus Krause schreef op 2025-02-26 11:22:
> Dear SDCC users,
> 
> would an _Optional qualifier (see N3422 -
> https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3422.pdf for details)
> be useful to you?
> 
> Basically, it would be a way for programmers to explicitly specify that
> a pointer might be null.
> 
> This would allow the compiler to warn on missing null pointer checks, 
> e.g.:
> 
> void f(_Optional char *p)
> {
> 	*p = 0; // Warning here
> }
> 
> void g(_Optional char *p)
> {
> 	if(p)
> 		*p = 0; // No warning here
> }
> 
> Since _Optional is essentially an opt-in mechanism, we would not get 
> any
> false warnings on existing code.
> 
> Philipp

Is there also a counterpart like _Required or _NonNull to indicate that 
the
pointer must already be checked to be non-null? It would have to be used 
in
the prototype of course. It could climb up the calling tree to a point
where the check is performed only once.

E.g.

void f(_NonNull char *p);
{
     *p = 0;     // No warning here
}

void g(char *p)
{
     f(p++);     // Warning here
     if (p)
     {
         f(p++); // No warning here
         f(p++); // No warning here
         f(p++); // No warning here
     }
}

For backward compatibility the choice to warn for neither keywords can 
be
done through pedantic setting.

Maarten