Re: passing NULL to a "char *" from tcl

On Sat, 1 Feb 2020 at 08:34, Mihir Luthra <[email protected]>
wrote:

> Hi,
>
> First of all, I found swig yesterday and seriously, AMAZING! Especially
> that guide for truly lazy people for writing interface file. Thanks for the
> tool!
>
> I posted on the list to receive some help regarding using C functions in
> tcl.
> I have compiled and loaded all packages successfully.
>
> The point where I am stuck is that my function looks like this in C:
>
> bool abc(void *a, char *b);
>
> Doc [1] says to pass NULL from tcl, we should pass "NULL". I need to pass
> both
> arguments NULL.
>
> I do like:
>
> abc "NULL" "NULL"
>
> This works well for first argument. But second argument treats NULL as a
> string instead. Can anyone help me with this?
>
>
The idea with SWIG is it provides a default type mapping and you can change
this if you want some other behaviour. In this case, char * expects a
proper string. You could modify the char * typemap to accept a TCL NULL.
I'm not very familiar with Tcl, so I'm afraid I can't help with that,
you'll need to know the Tcl C API in order to support this. I suggest you
take a look at typemaps.

Regards
William

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