[R-sig-Geo] followup on rgdal - invalid alignment error

[Tim Keitt]

One possibility is that the size of the GDAL data type is not the same
as the size of the R data type. This will definitely cause problems as
allocation is done by R and the pointer is cast to void when passed to
GDAL. My original C++ code simply assumes that both are 32-bit (or at
least equivalent size), but things will break if they are different.
(Roger -- you probably noticed the "fix me!" comments to myself in
there -- that was what I was talking about.)

GDAL data types include the size information (e.g., UInt32), but R
simply uses INTSXP and so on. Does anyone know how one determines for
any particular build of R the size of these R types? If I know the
size of INTSXP, then I can pick the corresponding GDAL data type.

THK

On 9/8/06, Roger Bivand <Roger.Bivand at nhh.no> wrote:
> On Fri, 8 Sep 2006, Scott W Mitchell wrote:
>
> > After sending my last post, detailing my system setup with a working
> > R/GDAL/rgdal installation on a Mac, I played a bit more and came
> > across a glitch when I tried example(readGDAL) on the fresh build.
>
> Scott:
>
> Thanks very much for your detailed descriptions, and I hope updating to
> try to help the original questioner hasn't broken things you need now.
>
> >
> > It gets through translating the data set and the image command, but
> > then on summary() I get:
>
> Can you re-run the example code by hand, line by line (copy & paste for
> example)? From what you write, image displays correctly, is that right?
> That suggests that the data has been read correctly, otherwise it would
> not have displayed? Which image is this - several are read in the example?
> Does example(GDAL.open) run smoothly? Something in the first band of the
> data is causing sort to choke, could it be an NA? can you copy out the
> band to a regular vector, and save it to file as an R object? If it is a
> value in the band, it should be saved in a platform independent way. GDAL
> also swaps to suit endianness.
>
> Roger
>
> >
> > rdGDAL> summary(x)
> >
> > *** caught bus error ***
> > address 0x17, cause 'invalid alignment'
> >
> > Traceback:
> > 1: sort(x, partial = unique(c(lo, hi)))
> > 2: quantile.default(object)
> > 3: stats::quantile(object)
> > 4: summary.default(X[[1]], ...)
> > 5: FUN(X[[1]], ...)
> > 6: lapply(as.list(object), summary, maxsum = maxsum, digits =
> > 12,     ...)
> > 7: summary.data.frame(object at att)
> > 8: summary(object at data)
> > 9: summary(object at data)
> > 10: summary(x)
> > 11: summary(x)
> > 12: eval.with.vis(expr, envir, enclos)
> > 13: eval.with.vis(ei, envir)
> > 14: source(zfile, local, echo = echo, prompt.echo = prompt.echo,
> > verbose = verbose, max.deparse.length = 250, encoding = encoding)
> > 15: example(readGDAL)
> >
> > Possible actions:
> > 1: abort (with core dump)
> > 2: normal R exit
> > 3: exit R without saving workspace
> > 4: exit R saving workspace
> > Selection:
> >
> > A byte-ordering issue???
> >
> > Any suggestions?
> >
> > Scott
> >
> >
> >
> >
> > ----
> > Scott Mitchell, Assistant Professor, Carleton University
> > Department of Geography & Environmental Studies, Loeb B443A
> > & Geomatics and Landscape Ecology Research Laboratory, Nesbitt 340
> > Mailing:  Loeb B349, 1125 Colonel By Dr., Ottawa, ON K1S 5B6 Canada
> > +1-613-520-2600 x2695 Fax: +1-613-520-4301 Scott_Mitchell at carleton.ca
> >
> > _______________________________________________
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> > R-sig-Geo at stat.math.ethz.ch
> > https://stat.ethz.ch/mailman/listinfo/r-sig-geo
> >
>
> --
> Roger Bivand
> Economic Geography Section, Department of Economics, Norwegian School of
> Economics and Business Administration, Helleveien 30, N-5045 Bergen,
> Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
> e-mail: Roger.Bivand at nhh.no
>
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-- 
Timothy H. Keitt
http://www.keittlab.org/