Debugging XS with duma/efence?

suaveant has asked for the wisdom of the Perl Monks concerning the following question:

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Re: Debugging XS with duma/efence? by renodino (Curate) on Nov 14, 2007 at 17:15 UTC
Are you using Perl's mem. mgmt. functions ? (Newz, Safefree, etc.) Or is this something external to the Perl environment (e.g., a shared library). If the latter, you might want to build an external stub and test/debug outside XS. As to using any debug heap mgrs, you probably already know that XS/Perl obsconds with the std. malloc/free symbols, so you need to create your own version in an externally compiled object. I've been using the following (you'll need to reference your own set of heap mgr libs/methods): Read more... crt_memmgt code (5 kB) Perl Contrarian & SQL fanboy	[reply] [d/l] [select]
Re^2: Debugging XS with duma/efence? by suaveant (Parson) on Nov 14, 2007 at 17:36 UTC
I basically wrote my own char by char ringbuffer parser for a product we connect to. I use a couple of linked lists. I am segfaulting on malloc, but when I clear out on of my free commands for the linked list everything runs smooth. I assume I am using freed memory somewhere and am trying to find out where. Duma does that but hooking it in seems problematic, at best. I can't easily compile the code outside of my module since it reads and writes Perl structures. All in all a nightmare :) - Ant - Some of my best work - (1 2 3)	[reply]
Re^2: Debugging XS with duma/efence? by suaveant (Parson) on Nov 14, 2007 at 19:57 UTC
Oh.. and I knew nothing of newz and safefree... I am looking into those now. Are you supposed to use them vs normal calloc free etc when writing C under Perl? (This is my first serious foray into XS) - Ant - Some of my best work - (1 2 3)	[reply]
Re^3: Debugging XS with duma/efence? by renodino (Curate) on Nov 14, 2007 at 20:04 UTC
Are you supposed to use them vs normal calloc free etc when writing C under Perl? Probably. See Memory Mgmt API in the perldocs. Perl Contrarian & SQL fanboy	[reply]
Re: Debugging XS with duma/efence? by dave_the_m (Monsignor) on Nov 14, 2007 at 23:08 UTC
If you're using Linux, just use valgrind. It will detect invalid uses of memory (eg accessing data that's been freed), and not only that, it will give you a stack dump at the point the freed block was illegally accessed, and at the point where that block was originally freed (with the option to attach gdb). It can do lots of other stuff too. And the best thing about it is you don't have to do any different compiling or linking: valgrind will run against standard binaries, eg `$ valgrind perl myprog.pl` [download] Dave.	[reply] [d/l]