Re: [Bug] hook: -Wanalyzer-deref-before-check warning in run_hooks_opt

> On Thu, Jan 08, 2026 at 08:24:01PM -0500, correctmost wrote:
>> Hi,
>> 
>> GCC 15.2.1 warns about a potential NULL pointer dereference in
>> run_hooks_opt on the master branch:
>> 
>> ---
>> 
>> ../hook.c: In function ‘run_hooks_opt’:
>> ../hook.c:167:12: error: check of ‘options’ for NULL after already dereferencing it [-Werror=analyzer-deref-before-check]
>>   167 |         if (!options)
>>       |            ^
>> 
>> [...snip...]
>> 
>>     │  156 |                 .ungroup = options->ungroup,
>>     │      |                            ~~~~~~~~~~~~~~~~
>>     │      |                                   |
>>     │      |                                   (7) pointer ‘options’ is dereferenced here
>>     │......
>>     │  167 |         if (!options)
>>     │      |            ~                           
>>     │      |            |
>>     │      |            (8)   pointer ‘options’ is checked for NULL here but it was already dereferenced at (7)
>>     │
>> 
>> ---
>> 
>> This does seem like a real bug, though I'm not sure how likely it is
>> to occur.  It looks like the warning was introduced in merge commit
>> f406b89552 ("Use hook API to replace ad-hoc invocation of hook scripts
>> with the run_command() API.").
>> 
>> I noticed the warning while compiling commit d529f3a19736 on Arch
>> Linux.
>
> It's not a real bug. If you take a look at the the `if (!options)`
> check, you'll see:
>
> 	if (!options)
> 		BUG("a struct run_hooks_opt must be provided to run_hooks");
>
> So we'd abort immediatly with an error message in case the pointer was
> `NULL`. Which clarifies that this is a case that shouldn't ever happen
> in the first place.
>
> That being said, it's of course a bit careless to dereference the
> pointer before we have the opportunity to call `BUG()`. I see two ways
> to fix this:
>
>   - We can either move all derefs of `options` after the call to
>     `BUG()`.
>
>   - Or we can drop the call to `BUG()` altogether.
>
> Out of those two I think I slightly lean towards the latter, mostly
> because the resulting code structure is simpler. And we'd reliably
> segfault anyway if we dereference the pointer, even though we would not
> get a clean error message. Not sure whether that really is worth the
> hassle though.