[Clang-21-git] New Wdefault-const-init-var-unsafe warnings with Kernel 6.14.4

[ms178]

Using clang version 21.0.0git (https://github.com/llvm/llvm-project.git 3015edf96e4faad0d367d0879269c1c905a4eec7), I see a lot of these new warnings when compiling Kernel 6.14.4. Is this a known issue?

In file included from drivers/target/target_core_tpg.c:21:
In file included from ./include/net/tcp.h:32:
In file included from ./include/net/inet_hashtables.h:26:
./include/net/ip.h:484:14: warning: default initialization of an object of type 'typeof (rt->dst.expires)' (aka 'const unsigned long') leaves the object uninitialized and is incompatible with C++ [-Wdefault-const-init-var-unsafe]
  484 |                 if (mtu && time_before(jiffies, rt->dst.expires))
      |                            ^
./include/linux/jiffies.h:138:26: note: expanded from macro 'time_before'
  138 | #define time_before(a,b)        time_after(b,a)
      |                                 ^
./include/linux/jiffies.h:128:3: note: expanded from macro 'time_after'
  128 |         (typecheck(unsigned long, a) && \
      |          ^
./include/linux/typecheck.h:11:12: note: expanded from macro 'typecheck'
   11 |         typeof(x) __dummy2; \
      |                   ^
In file included from drivers/target/target_core_tpg.c:21:
In file included from ./include/net/tcp.h:44:
In file included from ./include/net/xfrm.h:26:
./include/net/ip6_fib.h:271:10: warning: default initialization of an object of type 'typeof (f6i->expires)' (aka 'const unsigned long') leaves the object uninitialized and is incompatible with C++ [-Wdefault-const-init-var-unsafe]
  271 |                 return time_after(jiffies, f6i->expires);
      |                        ^
./include/linux/jiffies.h:129:3: note: expanded from macro 'time_after'
  129 |          typecheck(unsigned long, b) && \
      |          ^
./include/linux/typecheck.h:11:12: note: expanded from macro 'typecheck'
   11 |         typeof(x) __dummy2; \
      |                   ^
In file included from drivers/target/target_core_transport.c:27:
In file included from ./include/net/tcp.h:32:
In file included from ./include/net/inet_hashtables.h:26:
./include/net/ip.h:484:14: warning: default initialization of an object of type 'typeof (rt->dst.expires)' (aka 'const unsigned long') leaves the object uninitialized and is incompatible with C++ [-Wdefault-const-init-var-unsafe]
  484 |                 if (mtu && time_before(jiffies, rt->dst.expires))
      |                            ^
./include/linux/jiffies.h:138:26: note: expanded from macro 'time_before'
  138 | #define time_before(a,b)        time_after(b,a)
      |                                 ^
./include/linux/jiffies.h:128:3: note: expanded from macro 'time_after'
  128 |         (typecheck(unsigned long, a) && \
      |          ^
./include/linux/typecheck.h:11:12: note: expanded from macro 'typecheck'
   11 |         typeof(x) __dummy2; \
      |                   ^
In file included from drivers/target/target_core_transport.c:27:
In file included from ./include/net/tcp.h:44:
In file included from ./include/net/xfrm.h:26:
./include/net/ip6_fib.h:271:10: warning: default initialization of an object of type 'typeof (f6i->expires)' (aka 'const unsigned long') leaves the object uninitialized and is incompatible with C++ [-Wdefault-const-init-var-unsafe]
  271 |                 return time_after(jiffies, f6i->expires);
      |                        ^
./include/linux/jiffies.h:129:3: note: expanded from macro 'time_after'
  129 |          typecheck(unsigned long, b) && \
      |          ^
./include/linux/typecheck.h:11:12: note: expanded from macro 'typecheck'
   11 |         typeof(x) __dummy2; \
      |                   ^
2 warnings generated.
2 warnings generated.
In file included from drivers/target/iscsi/iscsi_target_login.c:17:
./include/net/ip.h:484:14: warning: default initialization of an object of type 'typeof (rt->dst.expires)' (aka 'const unsigned long') leaves the object uninitialized and is incompatible with C++ [-Wdefault-const-init-var-unsafe]
  484 |                 if (mtu && time_before(jiffies, rt->dst.expires))
      |                            ^
./include/linux/jiffies.h:138:26: note: expanded from macro 'time_before'
  138 | #define time_before(a,b)        time_after(b,a)
      |                                 ^
./include/linux/jiffies.h:128:3: note: expanded from macro 'time_after'
  128 |         (typecheck(unsigned long, a) && \
      |          ^
./include/linux/typecheck.h:11:12: note: expanded from macro 'typecheck'
   11 |         typeof(x) __dummy2; \
      |                   ^
1 warning generated.

[nathanchance]

Yes:

llvm/llvm-project#137166 (comment)

I plan to send a series to try and get this fixed today or tomorrow.

[ms178]

Hi @nathanchance , testing your v2 patchset with the same llvm-revision as before, I still get a lot of new warnings, this time for -Wunterminated-string-initialization which I didn't see on an older LLVM revision. Shall I open a new issue to track these? Are these a known issue, too?

drivers/net/ethernet/emulex/benet/be_cmds.c:2618:51: warning: initializer-string for character array is too long, array size is 16 but initializer has size 17 (including the null terminating character); did you mean to use the 'nonstring' attribute? [-Wunterminated-string-initialization]
 2618 | static char flash_cookie[2][16] = {"*** SE FLAS", "H DIRECTORY *** "};
      |                                                   ^~~~~~~~~~~~~~~~~~
1 warning generated.
drivers/net/wireguard/noise.c:28:38: warning: initializer-string for character array is too long, array size is 37 but initializer has size 38 (including the null terminating character); did you mean to use the 'nonstring' attribute? [-Wunterminated-string-initialization]
   28 | static const u8 handshake_name[37] = "Noise_IKpsk2_25519_ChaChaPoly_BLAKE2s";
      |                                      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/net/wireguard/noise.c:29:39: warning: initializer-string for character array is too long, array size is 34 but initializer has size 35 (including the null terminating character); did you mean to use the 'nonstring' attribute? [-Wunterminated-string-initialization]
   29 | static const u8 identifier_name[34] = "WireGuard v1 zx2c4 Jason@zx2c4.com";
      |                                       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2 warnings generated.
drivers/net/wireguard/cookie.c:29:56: warning: initializer-string for character array is too long, array size is 8 but initializer has size 9 (including the null terminating character); did you mean to use the 'nonstring' attribute? [-Wunterminated-string-initialization]
   29 | static const u8 mac1_key_label[COOKIE_KEY_LABEL_LEN] = "mac1----";
      |                                                        ^~~~~~~~~~
drivers/net/wireguard/cookie.c:30:58: warning: initializer-string for character array is too long, array size is 8 but initializer has size 9 (including the null terminating character); did you mean to use the 'nonstring' attribute? [-Wunterminated-string-initialization]
   30 | static const u8 cookie_key_label[COOKIE_KEY_LABEL_LEN] = "cookie--";
      |                                                          ^~~~~~~~~~
2 warnings generated.
drivers/power/supply/power_supply_sysfs.c:183:2: warning: initializer-string for character array is too long, array size is 31 but initializer has size 32 (including the null terminating character); did you mean to use the 'nonstring' attribute? [-Wunterminated-string-initialization]

[nathanchance]

Hi @nathanchance , testing your v2 patchset with the same llvm-revision as before, I still get a lot of new warnings, this time for -Wunterminated-string-initialization which I didn't see on an older LLVM revision. Shall I open a new issue to track these? Are these a known issue, too?

drivers/net/ethernet/emulex/benet/be_cmds.c:2618:51: warning: initializer-string for character array is too long, array size is 16 but initializer has size 17 (including the null terminating character); did you mean to use the 'nonstring' attribute? [-Wunterminated-string-initialization]
 2618 | static char flash_cookie[2][16] = {"*** SE FLAS", "H DIRECTORY *** "};
      |                                                   ^~~~~~~~~~~~~~~~~~
1 warning generated.
drivers/net/wireguard/noise.c:28:38: warning: initializer-string for character array is too long, array size is 37 but initializer has size 38 (including the null terminating character); did you mean to use the 'nonstring' attribute? [-Wunterminated-string-initialization]
   28 | static const u8 handshake_name[37] = "Noise_IKpsk2_25519_ChaChaPoly_BLAKE2s";
      |                                      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/net/wireguard/noise.c:29:39: warning: initializer-string for character array is too long, array size is 34 but initializer has size 35 (including the null terminating character); did you mean to use the 'nonstring' attribute? [-Wunterminated-string-initialization]
   29 | static const u8 identifier_name[34] = "WireGuard v1 zx2c4 Jason@zx2c4.com";
      |                                       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2 warnings generated.
drivers/net/wireguard/cookie.c:29:56: warning: initializer-string for character array is too long, array size is 8 but initializer has size 9 (including the null terminating character); did you mean to use the 'nonstring' attribute? [-Wunterminated-string-initialization]
   29 | static const u8 mac1_key_label[COOKIE_KEY_LABEL_LEN] = "mac1----";
      |                                                        ^~~~~~~~~~
drivers/net/wireguard/cookie.c:30:58: warning: initializer-string for character array is too long, array size is 8 but initializer has size 9 (including the null terminating character); did you mean to use the 'nonstring' attribute? [-Wunterminated-string-initialization]
   30 | static const u8 cookie_key_label[COOKIE_KEY_LABEL_LEN] = "cookie--";
      |                                                          ^~~~~~~~~~
2 warnings generated.
drivers/power/supply/power_supply_sysfs.c:183:2: warning: initializer-string for character array is too long, array size is 31 but initializer has size 32 (including the null terminating character); did you mean to use the 'nonstring' attribute? [-Wunterminated-string-initialization]

Fixed in mainline but the initial patches that disabled -Wunterminated-string-initialization for GCC 15 (1, 2, 3) need to be backported to stable for that one to apply properly.

[ms178]

Fixed in mainline but the initial patches that disabled -Wunterminated-string-initialization for GCC 15 (1, 2, 3) need to be backported to stable for that one to apply properly.

Thank you for the pointers, Nathan!