linux-kernel - Re: [PATCH 1/1] cachefiles: fix build with GCC 15

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Message-ID: <20250121224131.3845bfd7@pumpkin>
Date: Tue, 21 Jan 2025 22:41:31 +0000
From: David Laight <david.laight.linux@...il.com>
To: Brahmajit Das <brahmajit.xyz@...il.com>
Cc: dhowells@...hat.com, netfs@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] cachefiles: fix build with GCC 15

On Tue, 21 Jan 2025 22:19:11 +0000
David Laight <david.laight.linux@...il.com> wrote:

> On Tue, 21 Jan 2025 14:45:30 +0530
> Brahmajit Das <brahmajit.xyz@...il.com> wrote:
> 
> > While building with GCC 15 I noticed these build error
> > 
> > fs/cachefiles/key.c:12:9: error: initializer-string for array of ‘char’ is too long [-Werror=unterminated-string-initialization]
> >    12 |         "0123456789"                    /* 0 - 9 */
> >       |         ^~~~~~~~~~~~
> > cc1: all warnings being treated as errors
> > 
> > This due to GCC 15 having enabled -Wunterminated-string-initialization
> > by default[0]. Separating each characters to ensure NUL termination of
> > char array.
> > 
> > [0]: https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Wno-unterminated-string-initialization
> > 
> > Signed-off-by: Brahmajit Das <brahmajit.xyz@...il.com>
> > ---
> >  fs/cachefiles/key.c | 14 ++++++++------
> >  1 file changed, 8 insertions(+), 6 deletions(-)
> > 
> > diff --git a/fs/cachefiles/key.c b/fs/cachefiles/key.c
> > index bf935e25bdbe..555a0ec9eff4 100644
> > --- a/fs/cachefiles/key.c
> > +++ b/fs/cachefiles/key.c
> > @@ -8,12 +8,14 @@
> >  #include <linux/slab.h>
> >  #include "internal.h"
> >  
> > -static const char cachefiles_charmap[64] =
> > -	"0123456789"			/* 0 - 9 */
> > -	"abcdefghijklmnopqrstuvwxyz"	/* 10 - 35 */
> > -	"ABCDEFGHIJKLMNOPQRSTUVWXYZ"	/* 36 - 61 */
> > -	"_-"				/* 62 - 63 */
> > -	;
> > +static const char cachefiles_charmap[64] = {
> > +	'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', /* 0 - 9 */
> > +	'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', /* 10 - 35 */
> > +	'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', /* 10 - 35 */
> > +	'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', /* 36 - 61 */
> > +	'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', /* 36 - 61 */
> > +	'_', '-' /* 62 - 63 */
> > +};   
> 
> That is just horrid.
> I think there is a attribute that stops the warning.
> Or just convert to unsigned char [].

Bah, neither works, but see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117178
and https://gcc.gnu.org/pipermail/gcc-patches/2024-December/671714.html

If/when applied adding __attribute__((nonstring)) will disable the warning.

In this case just changing the [64] to [65] will do no harm.

But perhaps the warning should just be disabled for now.

	David



> 
> 	David
> 
> 
> >  
> >  static const char cachefiles_filecharmap[256] = {
> >  	/* we skip space and tab and control chars */  
>