Sorry for lateness, I was away on week-end.

Hello there. Unfortunately I can't find the Alien::igraph, did you post that somewhere? No matter though.

It's on a bitbucket repository only right now: https://bitbucket.org/fgabolde/alien-igraph

From a cursory look at the igraph library, it seems igraph API expects you to manage the allocation of igraph_t structure on your own. Either a static or malloc'ed struct, but you have to allocate it somewhere. From this I presume you'd want a chunk (sizeof(igraph_t)) of opaque data in your perl object, not an opaque pointer. HtH.

Like I said, I don't know much about C, but it does not look like the library expects me to allocate memory. From the API docs:

igraph_t g;
igraph_empty(&g, 0, 1);
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seems to be enough to get an initialized graph in g. If this were XS I'd just do that but I don't really understand how to drop down to C in Platypus.

This allocates memory, either on the stack or in the area for global memory:

igraph_t g;
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For Perl, you will need to allocate a buffer, more or less with:

use vars '$g';
$g = "\x00" x IGRAPH_T_SIZE;
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... and ideally you can call/compile sizeof(igraph_t) in C so your C compiler and Perl agree on how much memory should be allocated for it.

Alright, I think I get it now (and I very obviously need to step back and find a C book somewhere). Platypus even exposes a sizeof() method so I can try some stuff with that.

Thanks to all involved!