Re: A nasty, silent native-component gotcha (GB_BASE) - (follow-up on the uvicorn thread)

[Benoît Minisini <benoit.minisini@xxxxxxxxxxxxxxxx>]

Le 09/09/2026 à 00:20, Alarch a écrit :
> Dear Benoît, dear Claus, dear all,
>
> ...
>
> The mistake: my class' native struct did not have GB_BASE as its first
> field.
>
> typedef struct { llhttp_t parser; llhttp_settings_t settings; ... } 
> CLLHTTPPARSER;
>
> instead of
>
> typedef struct { GB_BASE ob;   /* forgot this */ llhttp_t parser; 
> llhttp_settings_t settings; ... } CLLHTTPPARSER;
>
> ...
>
> Two things I wanted to ask/suggest, now that I've found it:
>
> 1. Would a cheap sanity check be worth adding somewhere in 
> CLASS_register_class (or right after a native _new call, in debug builds
> only) - e.g. checking that the class pointer embedded at the start of
> a freshly allocated object still matches what was written at allocation
> time? I don't know the internals well enough to judge the cost/
> complexity, but even a debug-only assertion would have saved me a
> good few hours, since it would point straight at the object instead of
> crashing somewhere unrelated much later.

Sorry for your struggle with that bug, but I don't think it's possible 
to detect that mistake at compile time or at run time.

> 2. Would it be worth a short, explicit warning on the component-
> writing wiki page (with exactly this failure mode described), for
> anyone writing their first native class the way I did? I'm happy to
> draft that if it's welcome - it's exactly the kind of thing that's
> obvious in hindsight and invisible beforehand.

Feel free to add it on the wiki.

Anyway, it's a very common programming pattern to have a common part at 
the beginning of a structure when you implement dynamic object with 
inheritance in C.

Regards,

--
Benoît Minisini.