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Posted by Shaun Clowes on November 8, 2004, 10:40 am
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Hi Everyone,
I've been staring at this for hours now and I can't work out where I'm
leaking memory in a perl XS module I'm working on. Basically, I need to take
a tree of C structures:
typedef struct _SGraph {
char *name;
int size;
Graph list[];
} * Graph;
with a given head pointer and iterate through the graph and produce Perl
hashes which look like { name => "__root__", parent => undef, list = [ {
name => "child" }, parent => (ref to parent), list = ... } ]. I've got the
algorithm working a number of different ways but each one leaks memory. I'm
sending the current implementation along with this post, sorry for the long
post, this is the shortest example that demonstrates the issue.
Thanks,
Shaun
SV *RvFromRv_noinc(SV *ptRv)
{
return(newRV_noinc(SvRV(ptRv)));
}
HV *MakeHash(Graph ptGraph, SV *ptParent)
{
static HV *ptGraphStash = NULL;
HV *ptHash;
SV *ptSubHash;
AV *ptArray;
int i;
SV *ptResult;
if (ptGraphStash == NULL)
{
ptGraphStash = gv_stashpv("OGDL::Graph", 0);
if (!ptGraphStash)
ptGraphStash = (HV *) -1;
}
ptHash = (HV *) newHV();
if (!ptParent)
/* Storing &PL_sv_undef does not work */
hv_fetch(ptHash, "parent", 6, 1);
else
/* Store the reference to our parent */
hv_store(ptHash, "parent", 6, RvFromRv(ptParent), 0);
hv_store(ptHash, "name", 4, newSVpv(ptGraph->name, 0), 0);
ptResult = newRV_noinc((SV *) ptHash);
ptArray = newAV();
av_extend(ptArray, ptGraph->size);
for (i = 0; i < ptGraph->size; i++)
{
ptSubHash = MakeHash(ptGraph->nodes[i], ptResult);
av_push(ptArray, RvFromRv_noinc((SV *) ptSubHash));
}
hv_store(ptHash, "list", 4, newRV_noinc((SV *) ptArray), 0);
if (ptGraphStash && (ptGraphStash != (HV *) -1))
sv_bless(ptResult, ptGraphStash);
return(ptResult);
}
MODULE = OGDL::NativeParser PACKAGE = OGDL::NativeParser
SV *GraphFile(char *sFile)
{
SV *ptResult = NULL;
....
ptResult = MakeHash(*ptParser->g, NULL);
return(ptResult);
}
SV *
load(file)
char *file
PREINIT:
Graph ptGraph = NULL;
CODE:
/* Create perl hashes to return */
RETVAL = GraphFile(file);
OUTPUT:
RETVAL
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Posted by Ilya Zakharevich on November 8, 2004, 11:58 pm
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[A complimentary Cc of this posting was sent to
Shaun Clowes
> Hi Everyone,
>
> I've been staring at this for hours now and I can't work out where I'm
> leaking memory in a perl XS module I'm working on. Basically, I need to take
> a tree of C structures:
>
> typedef struct _SGraph {
> char *name;
> int size;
> Graph list[];
> } * Graph;
>
> with a given head pointer and iterate through the graph and produce Perl
> hashes which look like { name => "__root__", parent => undef, list = [ {
> name => "child" }, parent => (ref to parent), list = ... } ].
This creates an object with a cyclic refernce structure. You need to
"weaken" some references. Google, or look in Perl docs.
Hope this helps,
Ilya
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