Re: [RFC PATCH] libacpi: Fix cross building x86 on arm

[Jan Beulich <jbeulich@xxxxxxxx>]

On 23.08.2022 12:24, Bertrand Marquis wrote:
> --- a/tools/libacpi/mk_dsdt.c
> +++ b/tools/libacpi/mk_dsdt.c
> @@ -18,6 +18,16 @@
>  #include <stdlib.h>
>  #include <stdbool.h>
>  #if defined(CONFIG_X86)
> +/*
> + * When building on non x86 host, arch-x86/xen.h will include xen.h which 
> will
> + * try to include the arch xen.h (for example if built on arm, x86/xen.h will
> + * include xen.h which will include arch-arm.h).
> + * To prevent this effect, define x86 to have the proper sub arch included 
> when
> + * the compiler does not define it.
> + */
> +#if !(defined(__i386__) || defined(__x86_64__))
> +#define __x86_64__
> +#endif

Besides being confusing this depends on the order of checks in xen.h.

>  #include <xen/arch-x86/xen.h>
>  #include <xen/hvm/hvm_info_table.h>
>  #elif defined(CONFIG_ARM_64)

At the very least you will want to #undef the auxiliary define as soon
as practically possible.

But I think a different solution will want finding. Did you check what
the #include is needed for, really? I've glanced through the file
without being able to spot anything ... After all this is a build tool,
which generally can't correctly use many of the things declared in the
header.

> diff --git a/xen/include/public/arch-x86/xen.h 
> b/xen/include/public/arch-x86/xen.h
> index 58a1e87ee971..ea33a56eb6a0 100644
> --- a/xen/include/public/arch-x86/xen.h
> +++ b/xen/include/public/arch-x86/xen.h
> @@ -24,6 +24,7 @@
>   * Copyright (c) 2004-2006, K A Fraser
>   */
>  
> +/* TODO: when cross building, this will include the wrong arch header */
>  #include "../xen.h"

I'm firmly against adding such a comment in a public header, the more
that it's misleading: Cross-building of Xen, for example, works quite
fine. The issue is limited to HOSTCC != CC (or yet more precisely the
target architecture of each), afaict.

Jan