Ed Hartnett wrote:
Howdy Jeff,
Just an update: we have confirmed this bug and I am working on it
now. I have also added this to our automatic testing, so that we can
see it break here on our test machines, and ensure that once it's
fixed, it doesn't break again.
I will let you know when this fix is available in the snapshot -
hopefully not more than a few days from now...
Thanks again for find this!
Ed
Ed: I'm not sure if this is the part of the same bug, or a different
one. Attached is a C program that generates a compound variable from a
struct containing a 16 bit integer and a 64 bit integer. If I use the
gcc __packed__ attribute to turn off the padding for memory alignment, I
get this from an ncdump of the resulting file:
data:
phony_var = {20000, 844424930431968} ;
whereas the correct result
data:
phony_var = {20000, 30000} ;
is obtained when the __packed__ attribute is not set and padding is
added for memory alignment. However, as I noted in my original report,
the file is not readable on platforms with a different default memory
alignment.
This probably is the same bug, but if so this example shows how to
trigger it without having access to multiple platforms.
-Jeff
--
Jeffrey S. Whitaker Phone : (303)497-6313
Meteorologist FAX : (303)497-6449
NOAA/OAR/PSD R/PSD1 Email : Jeffrey.S.Whitaker@xxxxxxxx
325 Broadway Office : Skaggs Research Cntr 1D-113
Boulder, CO, USA 80303-3328 Web : http://tinyurl.com/5telg
#include <stdlib.h>
#include <stdio.h>
#include "netcdf.h"
#define ERRCODE 2
#define ERR(e) {printf("Error: %s\n", nc_strerror(e)); exit(ERRCODE);}
int
main()
{
int ncid, typeid, varid, dimid, retval;
char name[NC_MAX_NAME + 1];
int dimids[] = {0};
struct s1
{
short i;
long long j;
/*};*/
} __attribute__ ((__packed__));
struct s1 data[1];
/* Create some phony data. */
data[0].i = 20000;
data[0].j = 300000;
/* Create a file with a compound type. Write a little data. */
if ((retval = nc_create("test.nc", NC_NETCDF4, &ncid))) ERR(retval);;
printf("size of compound %d\n",sizeof(struct s1));
if ((retval = nc_def_compound(ncid, sizeof(struct s1), "cmp1", &typeid)))
ERR(retval);;
printf("offset i %d\n",NC_COMPOUND_OFFSET(struct s1,i));
if ((retval = nc_insert_compound(ncid, typeid, "i",
NC_COMPOUND_OFFSET(struct s1, i), NC_SHORT)))
ERR(retval);;
printf("offset j %d\n",NC_COMPOUND_OFFSET(struct s1,j));
if ((retval = nc_insert_compound(ncid, typeid, "j",
NC_COMPOUND_OFFSET(struct s1, j), NC_INT64)))
ERR(retval);;
if ((retval = nc_def_dim(ncid, "phony_dim", 1, &dimid))) ERR(retval);
if ((retval = nc_def_var(ncid, "phony_var", typeid, 1, dimids, &varid)))
ERR(retval);
nc_put_var(ncid, varid, data);
nc_close(ncid);
}
