Re: [PATCH 1/1] container_of: Document container_of_const() is preferred

[Matthew Wilcox]

On Tue, Jun 18, 2024 at 02:54:53PM +0200, Greg Kroah-Hartman wrote:
> > I didn't have any issues (apart from me misspelling function names ;)) with
> > GCC 12, neither in using container_of_const() in a static inline function
> > nor in using a static inline function as a _Generic() expression.
> 
> Really?  And how do you handle the pointer being either const or not,
> and propagating that back out as the return type?  I'd like to see your
> inline function please.

Here's how I did it for page_folio():

#define page_folio(p)           (_Generic((p),                          \
        const struct page *:    (const struct folio *)_compound_head(p), \
        struct page *:          (struct folio *)_compound_head(p)))

Is there something differently magic about container_of() that prevents
this trick from working?