[Bug c/115185] Missing "too long" warning when string-array size doesn't include NULL byte

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115185

--- Comment #21 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Wentao Zhang from comment #18)
> This produces warnings in kernel defconfig builds and they become errors due
> to 
> CONFIG_WERROR.
> 
> Cases I've observed so far:
> 
> 1. initialization    
> https://elixir.bootlin.com/linux/v6.10-rc7/source/drivers/pnp/quirks.c#L412
>    related definition


> https://elixir.bootlin.com/linux/v6.10-rc7/source/include/linux/pnp.h#L293

That is a real bug:
```
        for (f = pnp_fixups; *f->id; f++) {
                if (!compare_pnp_id(dev->id, f->id))
                        continue;
...
int compare_pnp_id(struct pnp_id *pos, const char *id)
{
        if (!pos || !id || (strlen(id) != 7))
                return 0;

....
```
strlen(id) is dependent on the value of the fixup function and what endian and
such.


> 2. initialization    
> https://elixir.bootlin.com/linux/v6.10-rc7/source/drivers/acpi/nhlt.c#L23
>    related definition
> https://elixir.bootlin.com/linux/v6.10-rc7/source/include/acpi/actbl.h#L69

This might be ok though but maybe the warning should be disabled for this
initialization (in the source).

> 3.
> https://elixir.bootlin.com/linux/v6.10-rc7/source/drivers/acpi/tables.c#L385
> 4. initialization    
> https://elixir.bootlin.com/linux/v6.10-rc7/source/drivers/acpi/acpica/
> acpredef.h#L187
>    related definition
> https://elixir.bootlin.com/linux/v6.10-rc7/source/drivers/acpi/acpica/
> aclocal.h#L296 

This looks ok but only indirectly uses strncmp.

> 5. initialization    
> https://elixir.bootlin.com/linux/v6.10-rc7/source/drivers/acpi/acpica/
> nsrepair.c#L66
>    related definition
> https://elixir.bootlin.com/linux/v6.10-rc7/source/drivers/acpi/acpica/
> aclocal.h#L373 

Likewise.


> 6. initialization    
> https://elixir.bootlin.com/linux/v6.10-rc7/source/drivers/acpi/acpica/
> nsrepair2.c#L114
>    related definition
> https://elixir.bootlin.com/linux/v6.10-rc7/source/drivers/acpi/acpica/
> nsrepair2.c#L28
> 7.
> https://elixir.bootlin.com/linux/v6.10-rc7/source/drivers/gpu/drm/display/
> drm_dp_dual_mode_helper.c#L163
> 8. initialization    
> https://elixir.bootlin.com/linux/v6.10-rc7/source/drivers/power/supply/
> power_supply_sysfs.c#L182
>    related definition
> https://elixir.bootlin.com/linux/v6.10-rc7/source/drivers/power/supply/
> power_supply_sysfs.c#L26 
> 9. https://elixir.bootlin.com/linux/v6.10-rc7/source/fs/proc/task_mmu.c#L648

This one is ok, I think.

> 
> It still triggers the warning even if "\0" is explicitly specified and the
> length is exactly MAX_PROP_NAME_LEN + 1 (31).

Filed as PR 116082.