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Re: [Xen-devel] [PATCH V3 4/8] xen/common: Introduce xrealloc_flex_struct() helper macros




On 29.08.19 10:21, Jan Beulich wrote:

Hi Jan

On 28.08.2019 20:23, Oleksandr wrote:
--- a/xen/include/xen/xmalloc.h
+++ b/xen/include/xen/xmalloc.h
@@ -35,6 +35,18 @@
   #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, type, field, nr)
({                        \
+    typeof(*(ptr)) *ptr_ =
(ptr);                                            \
+    /* Type checking: make sure that incoming pointer is of correct
type */  \
+    (void)((ptr) == (type
*)0);                                              \
+    (type *)_xrealloc(ptr_, offsetof(type, field[nr]),
__alignof__(type));   \
+})
+
What about

#define xrealloc_flex_struct(ptr, field, nr)                         \
     (typeof(ptr))_xrealloc(ptr, offsetof(typeof(*(ptr)), field[nr]), \
                            __alignof__(typeof(*(ptr))))

?

Even better. And works...

Thank you.


--
Regards,

Oleksandr Tyshchenko


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