[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: 20020313: ncendef error

This archive contains answers to questions sent to Unidata support through mid-2025. Note that the archive is no longer being updated. We provide the archive for reference; many of the answers presented here remain technically correct, even if somewhat outdated. For the most up-to-date information on the use of NSF Unidata software and data services, please consult the Software Documentation first.

  • Subject: Re: 20020313: ncendef error
  • Date: Thu, 19 Sep 2002 17:16:32 -0600
Hi Masaki Fukuda and V. Lakshmanan,

 "V. Lakshmanan" <address@hidden> wrote:

> I finally found the problem, thanks to valgrind.
> There is an uninitalized local variable at:
> 
> putget.c:1896     
>           void* xp;
> which should be:
>           void *xp = NULL;
> since that variable gets used in:
>            int lstatus = ncp->nciop->get(ncp->nciop, offset, extent,
>                                  RGN_WRITE, &xp);
>  and libsrc/posixio.c:486 uses it:
>          if (*vpp == NULL)
> 
> which is why my program would crash every
> once in a long while.

and Masaki Fukuda <address@hidden> wrote:

> I think the pointer expected to initialize NULL(see the patch which
> attached in this mail).
> 
> Am I correct?, Is this a bug?
> If correct, I'm appliciated that the bug fixed in the next version.

Thanks, you have both identified the same bug.  I used Purify to
verify that the appended patch in the libsrc/ directory gets rid of
all Uninitialized Memory Reads (UMRs) when running nc_test.  This fix
will be included in the next release, and you have both been added to
and acknowledged in the list of Credits for netCDF contributions at:

  http://www.unidata.ucar.edu/packages/netcdf/credits.html

--Russ

cvs diff: Diffing .
Index: nc.c
===================================================================
RCS file: /upc/share/CVS/netcdf-3/libsrc/nc.c,v
retrieving revision 2.119
diff -r2.119 nc.c
308c308
<       const void *xp;
---
>       const void *xp = NULL;
343c343
<       void *xp;
---
>       void *xp = NULL;
Index: putget.m4
===================================================================
RCS file: /upc/share/CVS/netcdf-3/libsrc/putget.m4,v
retrieving revision 2.47
diff -r2.47 putget.m4
130c130
<       void *xp;
---
>       void *xp = NULL;
321c321
<               void *xp;
---
>               void *xp = NULL;
587c587
<       void *xp;
---
>       void *xp = NULL;
731c731
<       const void *xp;
---
>       const void *xp = NULL;