Switching from WiX 3.0 to 3.5 decreased msi size from 100Mb to 4Mb?

After upgrading my installer build to WiX 3.5 the msi size fell from 100Mb down to only 4Mb! At first I thought some files were excluded from MSI, so I ran light.exe 3.0 and 3.5 with -v (verbose) and -notidy (to keep the temp files) options, checked the cab files, and indeed in case of 3.5 the cab file was 3.8Mb while the 3.0 produced 98Mb. Looking inside the cab, all the files seem to be present. Tried extracting both cabs -- the output looks identical. Finally, still not believing my eyes I installed the 4Mb MSI and 开发者_开发问答it worked! What can explain such a drastic difference? My current theory -- perhaps the new WiX uses new CAB compressin logic which detects duplicate files and creates references instead of adding the file multiple times? The MSI linking time dropped significantly as well... My program consists of 20+ folders with pretty much same DLLs duplicated in all of them...

Wix 3.5.0619.0 included the following change (from http://wix.sourceforge.net/releases/3.5.2519.0/history.txt):

Smart cabbing now catches ALL duplicate files, not just ones from the same source path (based on file hashes).

I have also observed a similar reduction in installer size after an upgrade from Wix 3.0 to 3.5. The above change would account for this, as there is some duplication in the files our installer is delivering, and these would only be picked up by file hashes not source paths.

Did you have different source paths in your 3.0 and the same source path in your 3.5?

WiX Smart Cabbing

Can you share the MSIs somewhere (feel free to contact me offline if you prefer, see http://robmensching.com)? There are no changes that I know of in WiX v3.5 that could cause that sort of drastic change... unless your .wxs files changed... or there is a bug. ;)