We shouldn't warn the user. We should support exports >4GB.

I've also just been bitten by this issue, trying to export from bamboo 2.4.1 to current 3.3 (via 3.1), there is no indication in the export/import process of the 4GB limit. I've lost a lot of time trying different things for something which is known not to work, but not advertised as such at either the import or export level. Sleeper issue that still needs fixing (and should be pretty simple to do)

We should return with a warning to the user that their Zip is probably corrupted if the resulting file is >= 4GB.

My understanding is that it will certainly be corrupt. I think it would be better to refuse to create something useless, rather than create it with a warning that may be ignored. What do others think?

The real solution is to use a compression file format that supports files larger than 4GB: See BAM-1647.

We should return with a warning to the user that their Zip is probably corrupted if the resulting file is >= 4GB. The warning should also be on the export page. Since it's usually the artifacts that blows out the size of the export, we can also make the suggestion of exporting without the artifacts

Also, there is a limitation with the current truezip library used by Bamboo to export Bamboo-home.

TrueZIP currently implements the ZIP32 specification only. This limits the maximum ZIP file length to 4GB and the compound size of the name and comment to 64KB per entry. If the Bamboo-Home is over 4gb then the export will fail!