linux-kernel - Re: [PATCH] Xen: don't warn about 2-byte wchar

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Date:	Mon, 16 May 2016 12:08:17 +0100 (BST)
From:	Stefano Stabellini <sstabellini@...nel.org>
To:	Arnd Bergmann <arnd@...db.de>
cc:	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	David Vrabel <david.vrabel@...rix.com>,
	Juergen Gross <jgross@...e.com>,
	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	Ian Campbell <ian.campbell@...rix.com>,
	Shannon Zhao <shannon.zhao@...aro.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Xen: don't warn about 2-byte wchar_t in efi

On Wed, 11 May 2016, Arnd Bergmann wrote:
> The XEN UEFI code has become available on the ARM architecture
> recently, but now causes a link-time warning:
> 
> ld: warning: drivers/xen/efi.o uses 2-byte wchar_t yet the output is to use 4-byte wchar_t; use of wchar_t values across objects may fail
> 
> This seems harmless, because the efi code only uses 2-byte
> characters when interacting with EFI, so we don't pass on those
> strings to elsewhere in the system, and we just need to
> silence the warning.
> 
> It is not clear to me whether we actually need to build the file
> with the -fshort-wchar flag, but if we do, then we should also
> pass --no-wchar-size-warning to the linker, to avoid the warning.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> Fixes: 37060935dc04 ("ARM64: XEN: Add a function to initialize Xen specific UEFI runtime services")

Given that drivers/xen/efi.c doesn't actually use any wchar_t, it is not
clear to me whether we need to pass -fshort-wchar either. However this
patch is correct any, so I committed it to xentip.


>  drivers/xen/Makefile | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/xen/Makefile b/drivers/xen/Makefile
> index 415f2869054b..8feab810aed9 100644
> --- a/drivers/xen/Makefile
> +++ b/drivers/xen/Makefile
> @@ -8,6 +8,7 @@ nostackp := $(call cc-option, -fno-stack-protector)
>  CFLAGS_features.o			:= $(nostackp)
>  
>  CFLAGS_efi.o				+= -fshort-wchar
> +LDFLAGS					+= $(call ld-option, --no-wchar-size-warning)
>  
>  dom0-$(CONFIG_ARM64) += arm-device.o
>  dom0-$(CONFIG_PCI) += pci.o
> -- 
> 2.7.0
>