linux-kernel - [PATCH v2 1/1] netfs: fix building with GCC 15

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Message-ID: <20250414144500.20934-1-listout@listout.xyz>
Date: Mon, 14 Apr 2025 20:14:57 +0530
From: Brahmajit Das <brahmajit.xyz@...il.com>
To: 
Cc: jlayton@...nel.org,
	David Howells <dhowells@...hat.com>,
	Paulo Alcantara <pc@...guebit.com>,
	netfs@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Subject: [PATCH v2 1/1] netfs: fix building with GCC 15

Since the Linux kernel initializes many non-C-string char arrays with
literals. While it would be possible to convert initializers from:
   { "BOOP", ... }
to:
   { { 'B', 'O', 'O', 'P' }, ... }
that is annoying.
Making -Wunterminated-string-initialization stay silent about char
arrays marked with nonstring would be much better.

Without the __attribute__((nonstring)) we would get the following build
error:
fs/netfs/fscache_cache.c:375:67: error: initializer-string for array of ‘char’ is too long [-Werror=unterminated-string-initialization]
  375 | static const char fscache_cache_states[NR__FSCACHE_CACHE_STATE] = "-PAEW";
      |                                                                   ^~~~~~~
...
fs/netfs/fscache_cookie.c:32:69: error: initializer-string for array of ‘char’ is too long [-Werror=unterminated-string-initialization]
   32 | static const char fscache_cookie_states[FSCACHE_COOKIE_STATE__NR] = "-LCAIFUWRD";
      |                                                                     ^~~~~~~~~~~~
cc1: all warnings being treated as errors

Upstream GCC has added this commit
622968990beee7499e951590258363545b4a3b57[0][1] which silences warning
about truncating NUL char when initializing nonstring arrays.

[0]: https://gcc.gnu.org/cgit/gcc/commit/?id=622968990beee7499e951590258363545b4a3b57
[1]: https://gcc.gnu.org/cgit/gcc/commit/?id=afb46540d3921e96c4cd7ba8fa2c8b0901759455

Thanks to Jakub Jelinek <jakub@....gnu.org> for the gcc patch.

Signed-off-by: Brahmajit Das <listout@...tout.xyz>
---
 fs/cachefiles/key.c       | 2 +-
 fs/netfs/fscache_cache.c  | 3 ++-
 fs/netfs/fscache_cookie.c | 3 ++-
 3 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/fs/cachefiles/key.c b/fs/cachefiles/key.c
index bf935e25bdbe..1d5685edd1c9 100644
--- a/fs/cachefiles/key.c
+++ b/fs/cachefiles/key.c
@@ -8,7 +8,7 @@
 #include <linux/slab.h>
 #include "internal.h"
 
-static const char cachefiles_charmap[64] =
+static const char cachefiles_charmap[64] __attribute((nonstring)) =
 	"0123456789"			/* 0 - 9 */
 	"abcdefghijklmnopqrstuvwxyz"	/* 10 - 35 */
 	"ABCDEFGHIJKLMNOPQRSTUVWXYZ"	/* 36 - 61 */
diff --git a/fs/netfs/fscache_cache.c b/fs/netfs/fscache_cache.c
index 9397ed39b0b4..ccfe52056ed3 100644
--- a/fs/netfs/fscache_cache.c
+++ b/fs/netfs/fscache_cache.c
@@ -372,7 +372,8 @@ void fscache_withdraw_cache(struct fscache_cache *cache)
 EXPORT_SYMBOL(fscache_withdraw_cache);
 
 #ifdef CONFIG_PROC_FS
-static const char fscache_cache_states[NR__FSCACHE_CACHE_STATE] = "-PAEW";
+static const char fscache_cache_states[NR__FSCACHE_CACHE_STATE]
+	__attribute__((nonstring)) = "-PAEW";
 
 /*
  * Generate a list of caches in /proc/fs/fscache/caches
diff --git a/fs/netfs/fscache_cookie.c b/fs/netfs/fscache_cookie.c
index d4d4b3a8b106..c455d1b0f440 100644
--- a/fs/netfs/fscache_cookie.c
+++ b/fs/netfs/fscache_cookie.c
@@ -29,7 +29,8 @@ static LIST_HEAD(fscache_cookie_lru);
 static DEFINE_SPINLOCK(fscache_cookie_lru_lock);
 DEFINE_TIMER(fscache_cookie_lru_timer, fscache_cookie_lru_timed_out);
 static DECLARE_WORK(fscache_cookie_lru_work, fscache_cookie_lru_worker);
-static const char fscache_cookie_states[FSCACHE_COOKIE_STATE__NR] = "-LCAIFUWRD";
+static const char fscache_cookie_states[FSCACHE_COOKIE_STATE__NR]
+	__attribute__((nonstring)) = "-LCAIFUWRD";
 static unsigned int fscache_lru_cookie_timeout = 10 * HZ;
 
 void fscache_print_cookie(struct fscache_cookie *cookie, char prefix)
-- 
2.49.0