On Sat, Mar 20, 2010 at 12:53:12PM +0000, Martin Kersten wrote:
> Update of /cvsroot/monetdb/MonetDB5/src/modules/kernel
> In directory sfp-cvsdas-1.v30.ch3.sourceforge.com:/tmp/cvs-serv10537
>
> Modified Files:
> Tag: Feb2010
> batcast.mx
> Log Message:
> Backport of possible dangerous double frees. No roll forward needed.
While your revised code looks indeed more efficient to me (as it allows
ATOMfromstr() --- well, at least strFromStr(); I cannot tell about other
"extern" (varsized) atoms --- to reuse a allocated temporary buffer),
I wonder whether/why the original experienced double frees?
Called with v==NULL,
ATOMfromstr() --- again, I refer only to strFromStr(); FromStr functions for
other "extern" (varsized) atoms might behave differently; IMHO, we don't
have any "contract" or "policies" for FromStr() implementations --- would
allocate a buffer for the result,
ATOMput() copies the value from the buffer to the BAT heap,
and then the buffer is (was) freed.
Looks very sound to me.
What am I missing?
I would be thankful for any enlightment.
Stefan
> Index: batcast.mx
> ===================================================================
> RCS file: /cvsroot/monetdb/MonetDB5/src/modules/kernel/batcast.mx,v
> retrieving revision 1.31.2.7
> retrieving revision 1.31.2.8
> diff -u -d -r1.31.2.7 -r1.31.2.8
> --- batcast.mx 18 Feb 2010 01:04:05 -0000 1.31.2.7
> +++ batcast.mx 20 Mar 2010 12:53:10 -0000 1.31.2.8
> @@ -248,6 +248,8 @@
> BAT *b,*bn;
> BATiter bi;
> BUN p, q, r = 0;
> + ptr v = NULL;
> + int len = 0;
>
> @:getBATdescriptor(bid, b, "batca...@1")@
> @:voidresultBAT(ty...@1,"batca...@1")@
> @@ -255,15 +257,12 @@
>
> BATaccessBegin(b, USE_TAIL, MMAP_SEQUENTIAL);
> BATloop(b, p, q) {
> - ptr v = NULL;
> - int len = 0;
> -
> ATOMfromstr(ty...@1, &v, &len, (char *) BUNtvar(bi, p));
> ATOMput(ty...@1, bn->T->vheap, Tloc(bn, r), v);
> - if (ATOMextern(ty...@1))
> - GDKfree(v);
> r++;
> }
> + if (ATOMextern(ty...@1))
> + GDKfree(v);
> BATsetcount(bn, BATcount(b));
> bunins_failed:
> BATaccessEnd(b, USE_TAIL, MMAP_SEQUENTIAL);
>
>
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--
| Dr. Stefan Manegold | mailto:stefan.maneg...@cwi.nl |
| CWI, P.O.Box 94079 | http://www.cwi.nl/~manegold/ |
| 1090 GB Amsterdam | Tel.: +31 (20) 592-4212 |
| The Netherlands | Fax : +31 (20) 592-4199 |
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Try the new software tools for yourself. Speed compiling, find bugs
proactively, and fine-tune applications for parallel performance.
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