* [Caml-list] Data_custom_val(v)
@ 2001-07-15 3:16 Alexander V. Voinov
2001-07-20 14:00 ` Xavier Leroy
0 siblings, 1 reply; 2+ messages in thread
From: Alexander V. Voinov @ 2001-07-15 3:16 UTC (permalink / raw)
To: caml
Hi Developers,
I forgot to mention that Data_custom_val(v) doesn't allow for
assignments in C++, instead I have to use
value blk = alloc_custom(...);
*(void **)&(Field(blk, 1)) = (void *)some_data;
Alexander
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^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [Caml-list] Data_custom_val(v)
2001-07-15 3:16 [Caml-list] Data_custom_val(v) Alexander V. Voinov
@ 2001-07-20 14:00 ` Xavier Leroy
0 siblings, 0 replies; 2+ messages in thread
From: Xavier Leroy @ 2001-07-20 14:00 UTC (permalink / raw)
To: Alexander V. Voinov; +Cc: caml
> I forgot to mention that Data_custom_val(v) doesn't allow for
> assignments in C++, instead I have to use
>
> value blk = alloc_custom(...);
> *(void **)&(Field(blk, 1)) = (void *)some_data;
Don't do that, because someday the data part of the custom block may
not be at offset 1.
What is wrong with
value blk = alloc_custom(...);
mytype * mydata = (mytype *) Data_custom_val(v);
*mydata = <initial value>;
or, more concisely,
*((mytype *) Data_custom_val(v)) = <initial value>;
Is it that evil C++ that don't let you do that?
- Xavier Leroy
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