Messages in this thread | | | Date | Fri, 16 Nov 2018 15:04:32 +0100 | From | Stefano Brivio <> | Subject | Re: [PATCH net-next v2] geneve: Use empty braces for addr6 initializer |
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On Mon, 12 Nov 2018 23:11:47 -0700 Nathan Chancellor <natechancellor@gmail.com> wrote:
> Clang warns: > > drivers/net/geneve.c:428:29: error: suggest braces around initialization > of subobject [-Werror,-Wmissing-braces] > struct in6_addr addr6 = { 0 }; > ^ > {} > > Most initializations of structs in the kernel seem to use this format.
Actually, even with this, we get a warning with gcc 4.4 and 4.8. I tried a few compilers:
$ gcc-4.4 --version | head -n1 rhel-6.9-gcc (GCC) 4.4.7 20120313 (Red Hat 4.4.7-18) $ gcc-4.8 --version | head -n1 rhel-7.5-gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-28) $ gcc-7.3 --version | head -n1 gcc-7.3-gcc (GCC) 7.3.0 $ gcc-8.2 --version | head -n1 gcc (Debian 8.2.0-9) 8.2.0 $ clang --version | head -n1 clang version 6.0.1-9.2 (tags/RELEASE_601/final)
$ cat init.c #include <linux/in6.h> int main() { struct in6_addr addr6 = INIT; return addr6.in6_u.u6_addr8[0]; }
$ gcc-4.4 -DINIT="{ }" -S -Wall -Wextra -o init init.c 2>&1 | grep warning | head -n1 init.c:5: warning: missing initializer $ gcc-4.4 -DINIT="{ 0 }" -S -Wall -Wextra -o init init.c 2>&1 | grep warning | head -n1 init.c:5: warning: missing braces around initializer $ gcc-4.4 -DINIT="{ { { 0 } } }" -S -Wall -Wextra -o init init.c 2>&1 | grep warning | head -n1
$ gcc-4.8 -DINIT="{ }" -S -Wall -Wextra -o init init.c 2>&1 | grep warning | head -n1 init.c:5:16: warning: missing initializer for field 'in6_u' of 'struct in6_addr' [-Wmissing-field-initializers] $ gcc-4.8 -DINIT="{ 0 }" -S -Wall -Wextra -o init init.c 2>&1 | grep warning | head -n1 init.c:5:16: warning: missing braces around initializer [-Wmissing-braces] $ gcc-4.8 -DINIT="{ { { 0 } } }" -S -Wall -Wextra -o init init.c 2>&1 | grep warning | head -n1
$ gcc-7.3 -DINIT="{ }" -S -Wall -Wextra -o init init.c 2>&1 | grep warning | head -n1 $ gcc-7.3 -DINIT="{ 0 }" -S -Wall -Wextra -o init init.c 2>&1 | grep warning | head -n1 $ gcc-7.3 -DINIT="{ { { 0 } } }" -S -Wall -Wextra -o init init.c 2>&1 | grep warning | head -n1
$ gcc-8.2 -DINIT="{ }" -S -Wall -Wextra -o init init.c 2>&1 | grep warning | head -n1 $ gcc-8.2 -DINIT="{ 0 }" -S -Wall -Wextra -o init init.c 2>&1 | grep warning | head -n1 $ gcc-8.2 -DINIT="{ { { 0 } } }" -S -Wall -Wextra -o init init.c 2>&1 | grep warning | head -n1
$ clang -DINIT="{ }" -S -Wall -Wextra -o init init.c 2>&1 | grep warning | head -n1 $ clang -DINIT="{ 0 }" -S -Wall -Wextra -o init init.c 2>&1 | grep warning | head -n1 init.c:5:33: warning: suggest braces around initialization of subobject [-Wmissing-braces] $ clang -DINIT="{ { { 0 } } }" -S -Wall -Wextra -o init init.c 2>&1 | grep warning | head -n1
So { { { 0 } } } seems to be the safest option. We could go with static but it looks even uglier to me.
Joe, suggestions?
-- Stefano
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