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

[Jan Beulich <jbeulich@xxxxxxxx>]

On 20.08.2019 20:09, Oleksandr Tyshchenko 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))
>   
> +/* Re-allocate space for a structure with a flexible array of typed objects. */
> +#define xrealloc_flex_struct(_ptr, _type, _field, _len) ({                   \
May I ask that you don't extend the bad use of leading underscores here?

> +    /* type checking: make sure that incoming pointer is of correct type */  \
Comment style (should start with upper case char)

> +    (void)((typeof(_ptr)) 0 == (_type *) 0);                                 \
Stray blanks before 0. And why not simply "(void)((ptr) == (type *)0)"?
(You'd need to avoid the double evaluation of ptr, yes.)

> +    ((_type *)_xrealloc(_ptr, offsetof(_type, _field[_len]),                 \
> +                        __alignof__(_type)));                                \
Unnecessary pair of outermost parentheses.

> +})
> +
> +/* Allocate space for a structure with a flexible array of typed objects. */
> +#define xmalloc_flex_struct(_type, _field, _len) \
> +    ((_type *)_xmalloc(offsetof(_type, _field[_len]), __alignof__(_type)))
I think this wants to go ahead of its re-alloc counterpart.

In both cases I'd also like to suggest using "nr" instead of "len",
as something called "length" can be mistaken to represent the
overall length of the resulting object, rather than the number of
array elements.

Jan

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