linux-kernel - Re: scripts/checkpatch: Concatenated strings should use spaces between elements

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Date:   Tue, 17 Oct 2017 16:18:51 -0700
From:   Joe Perches <joe@...ches.com>
To:     Heinrich Schuchardt <xypron.glpk@....de>,
        Andy Whitcroft <apw@...onical.com>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: scripts/checkpatch: Concatenated strings should use spaces
 between elements

On Wed, 2017-10-18 at 00:58 +0200, Heinrich Schuchardt wrote:
> On 10/18/2017 12:43 AM, Joe Perches wrote:
> > On Tue, 2017-10-17 at 23:17 +0200, Heinrich Schuchardt wrote:
> > > This patch creates a warning (CHECK)
> > > "Concatenated strings should use spaces between elements"
> > > 
> > > There are no concatenated strings here.
> > 
> > Yes, there are.
> > 
> > > (checkpatch is also used in the U-Boot project where wide strings
> > > occur in the EFI implementation.)
> > > 
> > > Signed-off-by: Heinrich Schuchardt <xypron.glpk@....de>
> > > ---
> > >  test.c | 7 +++++++
> > >  1 file changed, 7 insertions(+)
> > >  create mode 100644 test.c
> > > 
> > > diff --git a/test.c b/test.c
> > > new file mode 100644
> > > index 0000000000..dfd33cd765
> > > --- /dev/null
> > > +++ b/test.c
> > > @@ -0,0 +1,6 @@
> > > +#include <foo.h>
> > > +
> > > +void foo(void)
> > > +{
> > > +	test(L"\"");
> > 
> > In this case, L must be a constant string and you
> > are concatenating L and "\""
> > 
> > 
> 
> See ISO/IEC 9899:1999
> 
> 6.4.5 String literals
> 
> <cite>
> A character string literal is a sequence of zero or more multibyte
> characters enclosed in double-quotes, as in "xyz"
> A wide  string  literal is  the  same, except prefixed by the
> letter L.
> </cite>

Kernel doesn't support wide strings.

> L"foo" is a literal of type wchar_t * and not two strings.
> L is a qualifier and not a constant string.
> 
> Just like ULL in 10ULL.
> 
> Regards
> 
> Heinrich