Re: [Xen-devel] [PATCH] Xen: remove -fshort-wchar gcc flag

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 11.08.16 at 16:01, <arnd@xxxxxxxx> wrote:
> On Thursday, August 11, 2016 6:51:33 AM CEST Jan Beulich wrote:
>> >>> On 11.08.16 at 14:39, <arnd@xxxxxxxx> wrote:
>> > A previous patch added the --no-wchar-size-warning to the Makefile to
>> > avoid this harmless warning:
>> > 
>> > arm-linux-gnueabi-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
>> > 
>> > Changing kbuild to use thin archives instead of recursive linking
>> > unfortunately brings the same warning back during the final link.
>> > 
>> > This time, we remove the -fshort-wchar flag that originally caused
>> > the warning, hopefully fixing the problem for good. I don't see
>> > any reason for having the flag in the first place, as the Xen code
>> > does not use wchar_t at all.
>> 
>> It uses efi_char16_t, and by dropping -fshort-wchar you'd open
>> up a trap for anyone to fall into who were to add wide string
>> literals to that same file. EFI using 16-bit characters requires
>> code interfacing with EFI to do so too.
> 
> I don't understand. How is this different from other source files
> that use efi_char16_t or the wchar_t definition from include/linux/nls.h?

Perhaps they didn't run into the issue yet?

> As far as I can tell, they all use 16-bit characters, but none of the
> others sets the flag. Maybe we should just always build with -fshort-wchar
> from the top-level Makefile?

Quite possible, unless elsewhere in the tree 4-byte characters are
needed.

Jan


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