Hi Andrew,
> On 2 Feb 2024, at 00:39, Andrew Cooper <[email protected]> wrote: > > Wherever possible, it is a good idea to NULL out the visible reference to an > object prior to freeing it. The FREE*() macros already collect together both > parts, making it easy to adjust. > > This has a marginal code generation improvement, as some of the calls to the > free() function can be tailcall optimised. > Could you improve a bit the commit message and explain a bit why it is a good idea and also how the code might be improved because i do not get it ? Cheers Bertrand > No functional change. > > Signed-off-by: Andrew Cooper <[email protected]> > --- > CC: George Dunlap <[email protected]> > CC: Jan Beulich <[email protected]> > CC: Stefano Stabellini <[email protected]> > CC: Wei Liu <[email protected]> > CC: Julien Grall <[email protected]> > --- > xen/include/xen/mm.h | 3 ++- > xen/include/xen/xmalloc.h | 7 ++++--- > 2 files changed, 6 insertions(+), 4 deletions(-) > > diff --git a/xen/include/xen/mm.h b/xen/include/xen/mm.h > index 3d9b2d05a5c8..044f3f3b19c8 100644 > --- a/xen/include/xen/mm.h > +++ b/xen/include/xen/mm.h > @@ -92,8 +92,9 @@ bool scrub_free_pages(void); > > /* Free an allocation, and zero the pointer to it. */ > #define FREE_XENHEAP_PAGES(p, o) do { \ > - free_xenheap_pages(p, o); \ > + void *_ptr_ = (p); \ > (p) = NULL; \ > + free_xenheap_pages(_ptr_, o); \ > } while ( false ) > #define FREE_XENHEAP_PAGE(p) FREE_XENHEAP_PAGES(p, 0) > > diff --git a/xen/include/xen/xmalloc.h b/xen/include/xen/xmalloc.h > index 9ecddbff5e00..1b88a83be879 100644 > --- a/xen/include/xen/xmalloc.h > +++ b/xen/include/xen/xmalloc.h > @@ -66,9 +66,10 @@ > extern void xfree(void *p); > > /* Free an allocation, and zero the pointer to it. */ > -#define XFREE(p) do { \ > - xfree(p); \ > - (p) = NULL; \ > +#define XFREE(p) do { \ > + void *_ptr_ = (p); \ > + (p) = NULL; \ > + xfree(_ptr_); \ > } while ( false ) > > /* Underlying functions */ > > base-commit: 3f819af8a796c0e2f798dd301ec8c3f8cccbc9fc > -- > 2.30.2 > >
