[libcxx-commits] [clang] [libcxx] [Clang] Diagnose forming references to nullptr (PR #143667)

[via libcxx-commits]

NCLnclNCL wrote:

> I am seeing a new build failure when building the Linux kernel as a result of this change.
> 
> ```
> drivers/tty/sysrq.c:486:2: error: initializer element is not a compile-time constant
>   486 |         &sysrq_showlocks_op,            /* d */
>       |         ^~~~~~~~~~~~~~~~~~~
> ```
> 
> as a result of
> 
> ```c
> #ifdef CONFIG_LOCKDEP
> static void sysrq_handle_showlocks(u8 key)
> {
> 	debug_show_all_locks();
> }
> 
> static const struct sysrq_key_op sysrq_showlocks_op = {
> 	.handler	= sysrq_handle_showlocks,
> 	.help_msg	= "show-all-locks(d)",
> 	.action_msg	= "Show Locks Held",
> };
> #else
> #define sysrq_showlocks_op (*(const struct sysrq_key_op *)NULL)
> #endif
> ```
> 
> This build does not have LOCKDEP enabled so `&sysrq_showlocks_op` becomes `&(*(const struct sysrq_key_op *)((void *)0))`. Is the error expected in this case? I am not sure if this construct is used elsewhere in the kernel but it was in the first build that was attempted during a compiler upgrade.

How to fix ?

https://github.com/llvm/llvm-project/pull/143667