linux-kernel - [PATCH v2] isdn: avm: Fix string plus integer warning from Clang

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Date:   Wed,  9 Jan 2019 22:41:08 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Karsten Keil <isdn@...ux-pingi.de>,
        "David S. Miller" <davem@...emloft.net>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Nathan Chancellor <natechancellor@...il.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: [PATCH v2] isdn: avm: Fix string plus integer warning from Clang

A recent commit in Clang expanded the -Wstring-plus-int warning, showing
some odd behavior in this file.

drivers/isdn/hardware/avm/b1.c:426:30: warning: adding 'int' to a string does not append to the string [-Wstring-plus-int]
                cinfo->version[j] = "\0\0" + 1;
                                    ~~~~~~~^~~
drivers/isdn/hardware/avm/b1.c:426:30: note: use array indexing to silence this warning
                cinfo->version[j] = "\0\0" + 1;
                                           ^
                                    &      [  ]
1 warning generated.

This is equivalent to just "\0". Nick pointed out that it is smarter to
use "" instead of "\0" because "" is used elsewhere in the kernel and
can be deduplicated at the linking stage.

Link: https://github.com/ClangBuiltLinux/linux/issues/309
Suggested-by: Nick Desaulniers <ndesaulniers@...gle.com>
Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
---

v1 -> v2:

* Use "" instead of "\0", as they are equivalent, but "" can be
  deduplicated by the linker, as pointed out by Nick.

 drivers/isdn/hardware/avm/b1.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/isdn/hardware/avm/b1.c b/drivers/isdn/hardware/avm/b1.c
index 4ac378e48902..40ca1e8fa09f 100644
--- a/drivers/isdn/hardware/avm/b1.c
+++ b/drivers/isdn/hardware/avm/b1.c
@@ -423,7 +423,7 @@ void b1_parse_version(avmctrl_info *cinfo)
 	int i, j;
 
 	for (j = 0; j < AVM_MAXVERSION; j++)
-		cinfo->version[j] = "\0\0" + 1;
+		cinfo->version[j] = "";
 	for (i = 0, j = 0;
 	     j < AVM_MAXVERSION && i < cinfo->versionlen;
 	     j++, i += cinfo->versionbuf[i] + 1)
-- 
2.20.1