Hi,
I hope this bug hasn't been filed before, I couldn't find it
on the list via a quick check.
This concerns writing large (>4GB) variables in netcdf with
large-file-support. In netcdf-3.6.2/libsrc/var.c around line
400 it reads:
if( varp->xsz <= X_UINT_MAX / product )
/* if integer multiply will not overflow */
{
varp->len = product * varp->xsz;
} else {
/* OK for last var to be "too big", indicated by this special len */
varp->len = X_UINT_MAX;
}
switch(varp->type) {
case NC_BYTE :
case NC_CHAR :
case NC_SHORT :
if( varp->len%4 != 0 )
{
varp->len += 4 - varp->len%4; /* round up */
/* *dsp += 4 - *dsp%4; */
}
break;
default:
/* already aligned */
break;
}
In the case of NC_BYTE, NC_CHAR and NC_SHORT, varp->len will end
up being X_UINT_MAX+1 instead of X_UINT_MAX. This in turn causes
an assertion when calling ncx_put_size_t later:
ncx.c:1812: ncx_put_size_t: Assertion `*ulp <= 4294967295U' failed.
I could not think about a useful fix despite qualifying the
rounding with the product-overflow (just moved the else-part
further down):
if( varp->xsz <= X_UINT_MAX / product )
/* if integer multiply will not overflow */
{
varp->len = product * varp->xsz;
switch(varp->type) {
case NC_BYTE :
case NC_CHAR :
case NC_SHORT :
if( varp->len%4 != 0 )
{
varp->len += 4 - varp->len%4; /* round up */
/* *dsp += 4 - *dsp%4; */
}
break;
default:
/* already aligned */
break;
}
} else {
/* OK for last var to be "too big", indicated by this special len */
varp->len = X_UINT_MAX;
}
I hope this bug report is useful. If you can send me a better
patch against netcdf-3.6.2 I would highly appreciate it.
Cheers,
Mario Emmenlauer
--
Mario Emmenlauer Phone: +49-(0)761-203-8284
Institute for Computer Science Fax: +49-(0)761-203-8262
Chair of Pattern Recognition and Image Processing
Albert-Ludwigs-University
Georges-Koehler-Allee 052, room 01-022
79110 Freiburg mailto:emmenlau * informatik.uni-freiburg.de
Germany http://lmb.informatik.uni-freiburg.de/people/emmenlau/
