IDL 8.0 SAVE files that contain byte array variables cannot be restored in previous IDL versions.

Topic

If a save file that contains byte arrays or scalars is created using IDL 8.0, the resulting save file will only work in IDL 8.0, but it will fail in previous versions of IDL.

The solution is to install the IDL 8.0.1 patch.

Discussion

To reproduce the problem run IDL 8.0 and then execute the following lines:

### In IDL 8.0 ###

x = bytarr(100)
save, x, FILENAME='bytevariable.sav'

Then, go to an older version of IDL, for example IDL 7.1.1. You will see the following error message:

### In IDL 7.1 ###

IDL> restore, 'bytevariable.sav'
% RESTORE: Unexpected item code found in save file.
% RESTORE: Unexpected item code found in save file.
% RESTORE: End of file encountered. Unit: 100
File: C:\Documents and
Settings\mbowersox\bytevariable.sav
% Execution halted at: $MAIN$


Another possible error would be a segmentation fault that will close IDL DE completely.


Workaround

Install the IDL 8.0.1 patch. See the patch release notes, where you will find the following information:

ID:60178 --- IDL 8.0 SAVE files that contain scalar and array byte variables cannot be restored in previous IDL versions.

With the patch installed you can now restore IDL 8.0 SAVE files that include scalar and array byte variables in previous versions of IDL.

NOTE: Earlier versions of IDL may have problems restoring 8.0 SAVE files that include byte arrays greater than 2147483647 bytes.