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Re: [PATCH 3/6] xen/efi: Make efi-boot.h compile with -Wwrite-strings
- To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Tue, 21 Nov 2023 09:40:15 +0100
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- Cc: Roger Pau Monné <roger.pau@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, Roberto Bagnara <roberto.bagnara@xxxxxxxxxxx>, Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Tue, 21 Nov 2023 08:40:30 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 20.11.2023 23:49, Andrew Cooper wrote:
> GCC complains:
>
> In file included from arch/arm/efi/boot.c:700:
> arch/arm/efi/efi-boot.h: In function 'efi_arch_handle_cmdline':
> arch/arm/efi/efi-boot.h:482:16: error: assignment discards 'const'
> qualifier from pointer target type [-Werror=discarded-qualifiers]
> 482 | name.s = "xen";
> | ^
>
> There's no easy option. .rodata is really read-only, so the fact Xen doesn't
> crash means these strings aren't written to.
And the consuming sites confirm this being the case. Hence ...
> Lie to the compiler using a union.
... to at least slightly limit the lying, how about ...
> --- a/xen/arch/arm/efi/efi-boot.h
> +++ b/xen/arch/arm/efi/efi-boot.h
> @@ -479,7 +479,7 @@ static void __init efi_arch_handle_cmdline(CHAR16
> *image_name,
> w2s(&name);
> }
> else
> - name.s = "xen";
> + name.cs = "xen"; /* TODO, find a better way of doing this. */
>
> prop_len = 0;
> prop_len += snprintf(buf + prop_len,
... you also switch to using name.cs down below here and ...
> --- a/xen/arch/x86/efi/efi-boot.h
> +++ b/xen/arch/x86/efi/efi-boot.h
> @@ -324,7 +324,8 @@ static void __init efi_arch_handle_cmdline(CHAR16
> *image_name,
> w2s(&name);
> }
> else
> - name.s = "xen";
> + name.cs = "xen"; /* TODO, find a better way of doing this. */
> +
> place_string(&mbi.cmdline, name.s);
... here?
An alternative would be to introduce 'char xen[4] = "xen";' in both
cases, and use them instead of plain string literals.
Jan
|
