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Date: Fri, 11 Aug 2000 10:24:47 +0200
From: Xavier Leroy <Xavier.Leroy@inria.fr>
To: Markus Mottl <mottl@miss.wu-wien.ac.at>,
        Nicolas Joliot <Nicolas.Joliot@irisa.fr>
Cc: caml-list@inria.fr
Subject: Re: =?iso-8859-1?Q?Interfa=E7age_C=2FCAML?=
References: <3992D2D9.906E0BA7@irisa.fr> <20000810191404.A21178@miss.wu-wien.ac.at>
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In-Reply-To: <20000810191404.A21178@miss.wu-wien.ac.at>; from Markus Mottl on Thu, Aug 10, 2000 at 07:14:04PM +0200
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> [French>
>
> Si je le comprends bien, le problem c'est l'utilisation du
> "Store_double_field". La solution dans ce cas serait d'essayer le macro
> "Double_field" en place de l'autre macro.
> 
> C'est souvant un source des erreurs - peut-etre on pourrait changer le nom
> de "Store_double_field"? Il me semble que la plupart des programmeurs
> soient confuses par "Store"...
> 
> "Store_..." ne doit etre utilise que avec des "blocs structures", ou il
> sont obligatoirs.

> [English]
> 
> It seems that a common bug has struck again: using "Store_{whatever}" in
> C-interfaces is only allowed (and then mandatory) with structured blocks.
> Using it for anything else may crash the GC.

No, no, no!  Store_field can only be used (and is mandatory) for
structured blocks (with tag < No_scan_tag), but Store_double_field
can be used (and is mandatory) for blocks with tag Double_array_tag.

(If you do Double_field(array, n) = d, you'll run into alignment
problems on some platforms, e.g. the Sparc and Mips.)

So, Nicolas's code seems correct in this respect.

Nicolas: could you please send to caml@inria.fr (and not to caml-list)
a complete program that reproduces the crash?  There's not enough
details in your message to understand what goes wrong.

- Xavier Leroy