From: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
This patch introduces type-safe helper macros to re-allocate space
for a structure with a flexible array of typed objects.
For example, if we need to re-size an array with a single element:
struct arrlen
{
size_t len;
int data[1];
};
We can use the proposed macros in the following way:
new_ptr = realloc_flex_struct(old_ptr, data, nr_elem);
Subsequent patch will use this macros.
Also, while here, introduce xmalloc_flex_struct() to allocate space
for a structure with a flexible array of typed objects.
Suggested-by: Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>
Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
CC: Andrew Cooper <andrew.cooper3@citrix.com>
CC: George Dunlap <George.Dunlap@eu.citrix.com>
CC: Ian Jackson <ian.jackson@eu.citrix.com>
CC: Jan Beulich <jbeulich@suse.com>
CC: Julien Grall <julien.grall@arm.com>
CC: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
CC: Stefano Stabellini <sstabellini@kernel.org>
CC: Tim Deegan <tim@xen.org>
CC: Wei Liu <wl@xen.org>
CC: Paul Durrant <paul.durrant@citrix.com>
---
Changes V3 -> V4:
- clarified patch description
- modified to not use leading underscores
- removed unnecessary pair of outermost parentheses
- modified to use "nr" instead of "len"
- placed xmalloc_flex_struct before xrealloc_flex_struct
- simplified xrealloc_flex_struct macros
---
xen/include/xen/xmalloc.h | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/xen/include/xen/xmalloc.h b/xen/include/xen/xmalloc.h
index 831152f..f0736ce 100644
--- a/xen/include/xen/xmalloc.h
+++ b/xen/include/xen/xmalloc.h
@@ -35,6 +35,15 @@
#define xzalloc_array(_type, _num) \
((_type *)_xzalloc_array(sizeof(_type), __alignof__(_type), _num))
+/* Allocate space for a structure with a flexible array of typed objects. */
+#define xmalloc_flex_struct(type, field, nr) \
+ (type *)_xmalloc(offsetof(type, field[nr]), __alignof__(type))
+
+/* Re-allocate space for a structure with a flexible array of typed objects. */
+#define xrealloc_flex_struct(ptr, field, nr) \
+ (typeof(ptr))_xrealloc(ptr, offsetof(typeof(*(ptr)), field[nr]), \
+ __alignof__(typeof(*(ptr))))
+
/* Allocate untyped storage. */
#define xmalloc_bytes(_bytes) _xmalloc(_bytes, SMP_CACHE_BYTES)
#define xzalloc_bytes(_bytes) _xzalloc(_bytes, SMP_CACHE_BYTES)
--
2.7.4
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https://lists.xenproject.org/mailman/listinfo/xen-develOn 13.09.2019 17:35, Oleksandr Tyshchenko wrote:
> --- a/xen/include/xen/xmalloc.h
> +++ b/xen/include/xen/xmalloc.h
> @@ -35,6 +35,15 @@
> #define xzalloc_array(_type, _num) \
> ((_type *)_xzalloc_array(sizeof(_type), __alignof__(_type), _num))
>
> +/* Allocate space for a structure with a flexible array of typed objects. */
> +#define xmalloc_flex_struct(type, field, nr) \
> + (type *)_xmalloc(offsetof(type, field[nr]), __alignof__(type))
> +
> +/* Re-allocate space for a structure with a flexible array of typed objects. */
> +#define xrealloc_flex_struct(ptr, field, nr) \
> + (typeof(ptr))_xrealloc(ptr, offsetof(typeof(*(ptr)), field[nr]), \
> + __alignof__(typeof(*(ptr))))
With the missing parentheses around the entire constructs added
Reviewed-by: Jan Beulich <jbeulich@suse.com>
I'd like to note though that it sort of feels as if this notation
isn't going to provide maximum flexibility. I therefore wonder
whether the last two parameters shouldn't be combined, resulting
in an invocation like
ptr = xmalloc_flex_struct(struct s, field[5]);
But I realize this would allow for (more; I'll reply to patch 6
in a minute) abuse, so this wouldn't be a clear win.
Jan
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On 16.09.19 13:37, Jan Beulich wrote: Hi, Jan > On 13.09.2019 17:35, Oleksandr Tyshchenko wrote: >> --- a/xen/include/xen/xmalloc.h >> +++ b/xen/include/xen/xmalloc.h >> @@ -35,6 +35,15 @@ >> #define xzalloc_array(_type, _num) \ >> ((_type *)_xzalloc_array(sizeof(_type), __alignof__(_type), _num)) >> >> +/* Allocate space for a structure with a flexible array of typed objects. */ >> +#define xmalloc_flex_struct(type, field, nr) \ >> + (type *)_xmalloc(offsetof(type, field[nr]), __alignof__(type)) >> + >> +/* Re-allocate space for a structure with a flexible array of typed objects. */ >> +#define xrealloc_flex_struct(ptr, field, nr) \ >> + (typeof(ptr))_xrealloc(ptr, offsetof(typeof(*(ptr)), field[nr]), \ >> + __alignof__(typeof(*(ptr)))) > With the missing parentheses around the entire constructs added > Reviewed-by: Jan Beulich <jbeulich@suse.com> Thank you. > I'd like to note though that it sort of feels as if this notation > isn't going to provide maximum flexibility. I therefore wonder > whether the last two parameters shouldn't be combined, resulting > in an invocation like > > ptr = xmalloc_flex_struct(struct s, field[5]); > > But I realize this would allow for (more; I'll reply to patch 6 > in a minute) abuse, so this wouldn't be a clear win. Agree. -- Regards, Oleksandr Tyshchenko _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
Hi Jan > >> On 13.09.2019 17:35, Oleksandr Tyshchenko wrote: >>> --- a/xen/include/xen/xmalloc.h >>> +++ b/xen/include/xen/xmalloc.h >>> @@ -35,6 +35,15 @@ >>> #define xzalloc_array(_type, _num) \ >>> ((_type *)_xzalloc_array(sizeof(_type), __alignof__(_type), >>> _num)) >>> +/* Allocate space for a structure with a flexible array of typed >>> objects. */ >>> +#define xmalloc_flex_struct(type, field, nr) \ >>> + (type *)_xmalloc(offsetof(type, field[nr]), __alignof__(type)) >>> + >>> +/* Re-allocate space for a structure with a flexible array of typed >>> objects. */ >>> +#define xrealloc_flex_struct(ptr, field, >>> nr) \ >>> + (typeof(ptr))_xrealloc(ptr, offsetof(typeof(*(ptr)), >>> field[nr]), \ >>> + __alignof__(typeof(*(ptr)))) >> With the missing parentheses around the entire constructs added >> Reviewed-by: Jan Beulich <jbeulich@suse.com> > > Thank you. Would you be happy if I add xzalloc_flex_struct here as well (may I retain your R-b)? Actually the xzalloc_flex_struct better fits in [1] ... [1] https://www.mail-archive.com/xen-devel@lists.xenproject.org/msg55557.html -- Regards, Oleksandr Tyshchenko _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
On 20.09.2019 11:51, Oleksandr wrote: >>> On 13.09.2019 17:35, Oleksandr Tyshchenko wrote: >>>> --- a/xen/include/xen/xmalloc.h >>>> +++ b/xen/include/xen/xmalloc.h >>>> @@ -35,6 +35,15 @@ >>>> #define xzalloc_array(_type, _num) \ >>>> ((_type *)_xzalloc_array(sizeof(_type), __alignof__(_type), >>>> _num)) >>>> +/* Allocate space for a structure with a flexible array of typed >>>> objects. */ >>>> +#define xmalloc_flex_struct(type, field, nr) \ >>>> + (type *)_xmalloc(offsetof(type, field[nr]), __alignof__(type)) >>>> + >>>> +/* Re-allocate space for a structure with a flexible array of typed >>>> objects. */ >>>> +#define xrealloc_flex_struct(ptr, field, >>>> nr) \ >>>> + (typeof(ptr))_xrealloc(ptr, offsetof(typeof(*(ptr)), >>>> field[nr]), \ >>>> + __alignof__(typeof(*(ptr)))) >>> With the missing parentheses around the entire constructs added >>> Reviewed-by: Jan Beulich <jbeulich@suse.com> >> >> Thank you. > > > Would you be happy if I add xzalloc_flex_struct here as well (may I > retain your R-b)? Yes to both. Jan _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
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