Re^3: Wrapping a C shared library with Perl and XS

One of the approaches to freeing memory is to call free right after the last usage of a pointer (in our case it's the loop which calls inline_stack_push(sv_2mortal(newSViv(c_array[i])));) and set it to NULL afterwards.

Setting a pointer to NULL serves double purpose:

Checking for NULL is very easy, checking if non-NULL pointer is valid is very complex at best
If you defensively call free(c_array) in another part of the program, free(NULL) would be safe on modern libcs, while free of a freed pointer causes memory corruption

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Re^4: Wrapping a C shared library with Perl and XS by stevieb (Canon) on Mar 31, 2017 at 23:23 UTC
Thank you very much AnonyMonk! I especially appreciated the fact you used the term "our" in your reply, as it shows that even Anonymous Monk cares and has interest ;) I'll pull this back out over the weekend sometime and play around with it and run things against `valgrind`. Your feedback is appreciated in my curve of learning. I'll update the OP after I've played around.	[reply] [d/l]
Re^5: Wrapping a C shared library with Perl and XS by Anonymous Monk on Apr 06, 2017 at 17:38 UTC
I'll pull this back out over the weekend sometime and play around with it and run things against `valgrind`. I'm not sure about properly written `libperl` applications (i.e. ones creating `PerlInterpreter` objects and not forgetting to call `perl_destruct(my_perl); perl_free(my_perl); PERL_SYS_TERM();` afterwards), but `perl` itself is known to show leaks when checked by `valgrind`. As in, `$ valgrind perl -e1 2>&1 \| grep definitely ==12501== definitely lost: 7,075 bytes in 15 blocks` [download] Part of the reason for that might be to speed up termination: why bother calling `free()` if the process is going to die right now and the OS will pick up its resources anyway? But there are other possible reasons for valgrind to report a memory leak.	[reply] [d/l] [select]
Re^6: Wrapping a C shared library with Perl and XS by stevieb (Canon) on Apr 08, 2017 at 03:34 UTC
I still haven't got back to this yet, but I'm re-raising now that I'm back home to look into it. Thanks for the deep insight!	[reply]
Re^7: Wrapping a C shared library with Perl and XS by Anonymous Monk on May 08, 2017 at 12:37 UTC
Re^8: Wrapping a C shared library with Perl and XS by stevieb (Canon) on May 08, 2017 at 14:42 UTC


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