Re: [XEN PATCH v3 09/16] xen: address violations of MISRA C:2012 Directive 4.10

[Jan Beulich <jbeulich@xxxxxxxx>]

On 11.03.2024 09:59, Simone Ballarin wrote:
> Amend inclusion guards to address violations of
> MISRA C:2012 Directive 4.10 ("Precautions shall be taken in order
> to prevent the contents of a header file being included more than
> once").
> 
> Inclusion guards must appear at the beginning of the headers
> (comments are permitted anywhere) and the #if directive cannot
> be used for other checks.

This latter restriction, even if just slightly, hampers readability

> --- a/xen/include/xen/err.h
> +++ b/xen/include/xen/err.h
> @@ -1,5 +1,6 @@
> -#if !defined(__XEN_ERR_H__) && !defined(__ASSEMBLY__)
> -#define __XEN_ERR_H__
> +#ifndef XEN_INCLUDE_XEN_ERR_H
> +#define XEN_INCLUDE_XEN_ERR_H
> +#ifndef __ASSEMBLY__
>  
>  #include <xen/compiler.h>
>  #include <xen/errno.h>
> @@ -41,4 +42,5 @@ static inline int __must_check PTR_RET(const void *ptr)
>       return IS_ERR(ptr) ? PTR_ERR(ptr) : 0;
>  }
>  
> -#endif /* __XEN_ERR_H__ */
> +#endif /* __ASSEMBLY__ */
> +#endif /* XEN_INCLUDE_XEN_ERR_H */

... here, ...

> --- a/xen/include/xen/softirq.h
> +++ b/xen/include/xen/softirq.h
> @@ -1,5 +1,6 @@
> -#if !defined(__XEN_SOFTIRQ_H__) && !defined(__ASSEMBLY__)
> -#define __XEN_SOFTIRQ_H__
> +#ifndef XEN_INCLUDE_XEN_SOFTIRQ_H
> +#define XEN_INCLUDE_XEN_SOFTIRQ_H
> +#ifndef __ASSEMBLY__
>  
>  /* Low-latency softirqs come first in the following list. */
>  enum {
> @@ -40,4 +41,5 @@ void cpu_raise_softirq_batch_finish(void);
>   */
>  void process_pending_softirqs(void);
>  
> -#endif /* __XEN_SOFTIRQ_H__ */
> +#endif /* __ASSEMBLY__ */
> +#endif /* XEN_INCLUDE_XEN_SOFTIRQ_H */

... here, and ...

> --- a/xen/include/xen/vmap.h
> +++ b/xen/include/xen/vmap.h
> @@ -1,5 +1,6 @@
> -#if !defined(__XEN_VMAP_H__) && defined(VMAP_VIRT_START)
> -#define __XEN_VMAP_H__
> +#ifndef XEN_INCLUDE_XEN_VMAP_H
> +#define XEN_INCLUDE_XEN_VMAP_H
> +#ifdef VMAP_VIRT_START
>  
>  #include <xen/mm-frame.h>
>  #include <xen/page-size.h>
> @@ -42,4 +43,5 @@ static inline void vm_init(void)
>      vm_init_type(VMAP_DEFAULT, (void *)VMAP_VIRT_START, 
> arch_vmap_virt_end());
>  }
>  
> -#endif /* __XEN_VMAP_H__ */
> +#endif /* VMAP_VIRT_START */
> +#endif /* XEN_INCLUDE_XEN_VMAP_H */

... here. Wasn't a goal of Misra to also not have negative effects on code
readability?

Jan