Re: [Tarantool-patches] [PATCH luajit 1/2] build: introduce LUAJIT_USE_UBSAN option

[Sergey Kaplun via Tarantool-patches <tarantool-patches@dev.tarantool.org>]

Hi, folks!
Some more thoughts below.

On 15.05.24, Sergey Kaplun wrote:

<snipped>

> +  string(JOIN "," UBSAN_IGNORE_OPTIONS
> +    # Misaligned pseudo-pointers are used to determine internal
> +    # variable names inside the `for` cycle.
> +    alignment
> +    # Not interested in float cast overflow errors.
> +    float-cast-overflow
> +    # NULL checking is disabled because this is not a UB and
> +    # raises lots of false-positive fails.
> +    null

Maybe it is worth to add also "nonnull-attribute" to the ignore options:

```
LSAN_OPTIONS="abort_on_error=1" src/luajit -e 'error("bad usage", 3)'
/home/burii/builds_workspace/luajit/gh-8473-ubsan/src/lj_buf.h:75:25: runtime error: null pointer passed as argument 1, which is declared to never be null
/usr/include/string.h:44:28: note: nonnull attribute specified here
```

Here, `memcpy()` gets the NULL pointer as the first argument and the
`len` == 0. So there are no problems here. Also, the nullability
violation is not a UB, as mentioned in the documentation.

Thoughts?

> +    # Not interested in checking arithmetic with NULL.
> +    pointer-overflow
> +    # Shifts of negative numbers are widely used in parsing ULEB,
> +    # cdata arithmetic, vmevent hash calculation, etc.
> +    shift-base
> +  )

-- 
Best regards,
Sergey Kaplun