Re: Having memory leak issues with perl-c
demerphq <[email protected]> Thu, 4 Aug 2022 21:10:57 +0200
| Newsgroups | gmane.comp.lang.perl.quality-assurance |
|---|---|
| Message-ID | <CANgJU+W95nxb9HB_EEXUo3KDYqx-1xe14TZmJG_v-RBD=evZpw@mail.gmail.com> |
--000000000000b5508f05e56f1c26 Content-Type: text/plain; charset="UTF-8" On Thu, 4 Aug 2022 at 17:04, Mark Murawski <[email protected]> wrote: > On 8/4/22 02:50, demerphq wrote: > > On Thu, 4 Aug 2022 at 01:58, Mark Murawski <[email protected]> > wrote: > >> I'm still not getting something... if I want to fix the code-as-is and do >> this: >> >> FNsv = get_sv("main::_FN", GV_ADD); >> if (!FNsv) >> ereport(ERROR, >> (errcode(ERRCODE_EXTERNAL_ROUTINE_EXCEPTION), >> errmsg("couldn't fetch $_FN"))); >> >> save_item(FNsv); /* local $_FN */ >> > > I dont get the sequence here. You take the old value of $main::_FN and > then you localize it after you fetch it? That seems weird. > > You did not respond to this comment ^^ > > >> >> hv = newHV(); // create new hash >> hv_store_string(hv, "name", cstr2sv(desc->proname)); >> > > Really you shouldnt do this until you have safely managed the refcounts of > all your newly created objects so that if this die's nothing leaks. > > > I take this to mean , setting up FNsv first, and then allocating hv? But > in this case we seem to have a chicken/egg problem? How can you set up > FNsv to point to hv without first setting up hv? > No, you shouldn't do anything after creating the hash that might die until you have arranged for hv to be freed. Storing into the hash might die. > > WARNING: Attempt to free unreferenced scalar: SV 0x55d5b1cf6480, Perl >> interpreter: 0x55d5b17226c0 >> > > Why are you decrementing hv? You dont own hv anymore, it's owned by svFN > and after the sv_setsv() call also FNsv. You shouldnt mess with its > refcount anymore. > > > The ownership aspect is making more sense now, thanks for clarifying. > YW. > > Obviously in perl we can write: > > my %hash; > $main::_FN= \%hash; > > And in XS we can do the same thing. Unfortunately there isn't a utility > sub to do this currently, it has been on my TODO list to add one for some > time but lack of round tuits and all that. > > You want code something like this: > > sv_clear(FNsv); /* undef the sv */ > sv_upgrade(FNsv,SVt_RV); > SvRV_set(FNsv, (SV*)hv); > SvROK_on(FNsv); > > Again, make liberal use of sv_dump() it is the XS version of Data::Dumper > more or less. > > > I have been playing with sv_dump()... At the end of this flow, the > refcount to FNsv is 1 and should get automatically cleaned up by Perl, > right? > Well I dont know for sure as I dont know the latest state of your code. But my thinking is that you asked for $main::_FN which is in the package table, so perl should clean it up. But I dont understand why you are using save_item(FNsv). > I still have a leak here, using the above code. > Probably I would be able to help you better if you posted the latest state of your code, with sv_dump() calls liberally sprinkled through the code, and post the output as well. > > Also... i get a crash when I use sv_clear(FNsv); right away like this. > And what does FNsv look like immediately before you call sv_clear()? > If I take it out, the code seems to all run correctly, but I have a leak > and the hash or the hash reference is not being cleaned up. > Can you please show a reduced version of the code? And explain why you are doing save_item(FNsv)? And provide some of the output of sv_dump()? cheers, Yves -- perl -Mre=debug -e "/just|another|perl|hacker/" --000000000000b5508f05e56f1c26 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable <div dir=3D"ltr"><div dir=3D"ltr">On Thu, 4 Aug 2022 at 17:04, Mark Murawsk= i <<a href=3D"mailto:[email protected]">markm-lists@intellasof= t.net</a>> wrote:<br></div><div class=3D"gmail_quote"><blockquote class= =3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rg= b(204,204,204);padding-left:1ex"> =20 =20 =20 <div> <div>On 8/4/22 02:50, demerphq wrote:<br> </div> <blockquote type=3D"cite"> =20 <div dir=3D"ltr"> <div dir=3D"ltr">On Thu, 4 Aug 2022 at 01:58, Mark Murawski <<a = href=3D"mailto:[email protected]" target=3D"_blank">markm-lists@i= ntellasoft.net</a>> wrote:<br> </div> <div class=3D"gmail_quote"> <blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8= ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"> <div> <div>I'm still not getting something... if I want to fix the code-as-is and do this:<br> </div> <br> =C2=A0=C2=A0=C2=A0 FNsv =3D get_sv("main::_FN", GV_= ADD);<br> =C2=A0=C2=A0=C2=A0 if (!FNsv)<br> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 ereport(ERROR,<br> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 (errcode(ERRCODE_EXTERNAL_ROUTINE_EXCEPTION),<br> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 errmsg("couldn't fetch $_FN&q= uot;)));<br> <br> =C2=A0=C2=A0=C2=A0 save_item(FNsv);=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 /* local $_FN */<br> </div> </blockquote> <div><br> </div> <div>I dont get the sequence here. You take the old value of $main::_FN and then you localize it after you fetch it? That seems weird.</div></div></div></blockquote></div></blockquote><= div><br></div><div>You did not respond to this comment ^^</div><div>=C2=A0<= /div><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;bo= rder-left:1px solid rgb(204,204,204);padding-left:1ex"><div><blockquote typ= e=3D"cite"><div dir=3D"ltr"><div class=3D"gmail_quote"> <div>=C2=A0</div> <blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8= ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"> <div> <br> =C2=A0=C2=A0=C2=A0 hv =3D newHV(); // create new hash<br> =C2=A0=C2=A0=C2=A0 hv_store_string(hv, "name", cstr2sv(desc->proname));<br> </div> </blockquote> <div><br> </div> <div>Really you shouldnt do this until you have safely managed the refcounts of all your newly created objects so that if this die's nothing leaks.</div> </div> </div> </blockquote> <br> I take this to mean , setting up FNsv first, and then allocating hv?=C2=A0 But in this case we seem to have a chicken/egg problem?=C2=A0= How can you set up FNsv to point to hv without first setting up hv?<br></di= v></blockquote><div><br></div><div>No, you shouldn't do anything after = creating the hash that might die until you have arranged for hv to be freed= . Storing into the hash might die.</div><div><br></div><blockquote class=3D= "gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(2= 04,204,204);padding-left:1ex"><div> <br> <br> <blockquote type=3D"cite"> <div dir=3D"ltr"> <div class=3D"gmail_quote"> <blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8= ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"> <div> WARNING:=C2=A0 Attempt to free unreferenced scalar: SV 0x55d5b1cf6480, Perl interpreter: 0x55d5b17226c0<br> </div> </blockquote> <div><br> </div> <div>Why are you decrementing hv? You dont own hv anymore, it's owned by svFN and after the sv_setsv() call also FNsv. You shouldnt mess with its refcount anymore.</div> </div> </div> </blockquote> <br> The ownership aspect is making more sense now, thanks for clarifying.<br></div></blockquote><div><br></div><div>YW.</div><div>=C2= =A0</div><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8e= x;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div> <br> <blockquote type=3D"cite"> <div dir=3D"ltr"> <div class=3D"gmail_quote"> <div>Obviously in perl we can write:</div> <div><br> </div> <div>my %hash;</div> <div>$main::_FN=3D \%hash;</div> <div><br> </div> <div>And in XS we can do the same thing. Unfortunately there isn't=C2=A0a utility sub to do this currently, it has=C2=A0= been on my TODO list to add one for some time but lack of round=C2=A0tuits and all that.=C2=A0</div> <div><br> </div> <div>You want code something like this:</div> <div><br> </div> <div>sv_clear(FNsv); /* undef the sv */</div> <div>sv_upgrade(FNsv,SVt_RV);</div> <div>SvRV_set(FNsv, (SV*)hv);</div> <div>SvROK_on(FNsv);</div> <div><br> </div> <div>Again, make liberal use of sv_dump() it is the XS version of <a>Data::Dumper</a> more or less.</div> </div> </div> </blockquote> <br> I have been playing with sv_dump()... At the end of this flow, the refcount to FNsv is 1 and should get automatically cleaned up by Perl, right?=C2=A0 </div></blockquote><div><br></div><div>Well I dont k= now for sure as I dont know the latest state of your code. But my thinking = is that you asked for $main::_FN which is in the package table, so perl sho= uld clean it up. But I dont understand why you are=C2=A0using save_item(FNs= v).</div><div>=C2=A0</div><blockquote class=3D"gmail_quote" style=3D"margin= :0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"= ><div>I still have a leak here, using the above code.<br></div></blockquote= ><div><br></div><div>Probably I would be able to help you=C2=A0 better if y= ou posted the latest state of your code, with sv_dump() calls liberally spr= inkled through the code, and post the output as well.</div><div>=C2=A0</div= ><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border= -left:1px solid rgb(204,204,204);padding-left:1ex"><div> <br> Also... i get a crash when I use sv_clear(FNsv); right away like this.<br></div></blockquote><div><br>And what does FNsv look like immed= iately before you call sv_clear()?=C2=A0</div><div>=C2=A0</div><blockquote = class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px sol= id rgb(204,204,204);padding-left:1ex"><div> If I take it out, the code seems to all run correctly, but I have a leak and the hash or the hash reference is not being cleaned up.</div><= /blockquote><div><br></div><div>Can you please show a reduced version of th= e code? And explain why you are doing save_item(FNsv)? And provide some of = the output of sv_dump()?</div><div><br></div><div>cheers,</div><div>Yves</d= iv><div><br></div></div>-- <br><div dir=3D"ltr" class=3D"gmail_signature">p= erl -Mre=3Ddebug -e "/just|another|perl|hacker/"</div></div> --000000000000b5508f05e56f1c26--