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Re: [PATCH] xen/decompress: resolve MISRA R5.5 identifier/macro name conflicts


  • To: Dmytro Prokopchuk1 <dmytro_prokopchuk1@xxxxxxxx>
  • From: Jan Beulich <jbeulich@xxxxxxxx>
  • Date: Fri, 22 May 2026 08:10:55 +0200
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  • Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Anthony PERARD <anthony.perard@xxxxxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, Julien Grall <julien@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
  • Delivery-date: Fri, 22 May 2026 06:11:17 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 21.05.2026 22:18, Dmytro Prokopchuk1 wrote:
> Convert 'malloc' and 'free' macros in 'decompress.h' from object-like
> to function-like form.
> 
> The object-like macros '#define free xfree' perform unconditional text
> replacement, causing conflicts with struct field 'free' in 'page_info'
> unions. Function-like macros only match when followed by parentheses,
> allowing 'free' to be used both as a macro and as a struct field without
> conflicts.

At the same time function-like macros cannot be used to e.g. pass the
(underlying) function pointer to a function. Likely there aren't any
such uses here, but imo this aspect needs covering in patches like
this one.

> Applying function-like form to both 'malloc' and 'free' ensures consistent
> macro style.

Not quite, seeing ...

> --- a/xen/common/decompress.h
> +++ b/xen/common/decompress.h
> @@ -9,8 +9,8 @@
>  #include <xen/types.h>
>  #include <xen/xmalloc.h>
>  
> -#define malloc xmalloc_bytes
> -#define free xfree
> +#define malloc(a) xmalloc_bytes(a)
> +#define free(a) xfree(a)
>  
>  #define large_malloc xmalloc_bytes
>  #define large_free xfree

... these two in context? IOW if you mean to achieve consistency,
convert these (and whatever else, if anything) as well?

Jan



 


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