Marcus Holland-Moritz <[EMAIL PROTECTED]> writes:
>I'm wondering if someone else ever wanted to do this...
>
>Deep inside my XS module I create an object and pass it to
>a function (which may pass it to other functions and so on).
>However, any of these functions may call Perl_croak(), and
>if they do, I need to destroy the object if I don't want to
>leak memory. Here's an excerpt of the original code:
>
> tag = tag_new(tagid, gs_TagTbl[tagid].vtbl);
> rv = gs_TagTbl[tagid].set(aTHX_ ptti, tag, val);
> insert_tag(ptl, tag);
>
>Calling the 'set' method in the second line may eventually
>call croak(). If it does, I just want to throw away the tag
>object and croak() again.
>
>I didn't find anything in perl(xs|guts|call|api), so I looked
>at how "eval" does it, and came up with the following macros:
>
> #define dXCPT dJMPENV; int rEtV = 0
>
> #define XCPT_TRY_START JMPENV_PUSH(rEtV); \
> if (rEtV == 0)
>
> #define XCPT_TRY_END JMPENV_POP;
>
> #define XCPT_CATCH if (rEtV != 0)
>
> #define XCPT_RETHROW JMPENV_JUMP(rEtV)
>
>With these macros, I can rewrite the above code as:
>
> dXCPT;
>
> tag = tag_new(tagid, gs_TagTbl[tagid].vtbl);
>
> XCPT_TRY_START {
> rv = gs_TagTbl[tagid].set(aTHX_ ptti, tag, val);
> } XCPT_TRY_END
>
> XCPT_CATCH
> {
> tag_delete(tag);
> XCPT_RETHROW;
> }
>
> insert_tag(ptl, tag);
>
>This seems to work fine, but makes use of internal API.
Which is why I have to date avoid this and done this kind of thing
one of two ways:
A. Make the "object" a perl level object (as well)
and give the perl class a DESTROY method which discards
the C/C++ objuect.
B. Wrap the callback (your .set) in a perl XS 'cv'
and call that via call_sv(cv,G_EVAL)
and the test SvTRUE(ERRSV)
>
>Is this the way to do it?
I am not entirely sure.
>Or is there any other/better way?
Two other ways above...
>
>If it turns out to be correct, would it make sense to document
>it and/or add some public interface for this purpose?
That would be good.
>
>Marcus
