Can support be added for setup.exe to be compiled as a 64-bit app for Product Configurations whose Template Summary contains x64 or Intel64? Then, if a project includes setup/feature prerequisites and the end user attempts to run the 64-bit setup.exe on a 32-bit machine, setup.exe would display an error message saying that the processor type is not supported and nothing, including the prerequisites, gets installed.
While actually making this a 64-bit executable is possible, I don't think that's the right idea. However I agree that it makes sense to support that check in the 32-bit bootstrap - i.e. to require a matching 64-bit architecture before doing anything else. However when this really makes sense is for a truly 64-bit package, and its prerequisites should probably be conditioned on a 64-bit OS (and thus wouldn't install in this case).
Does it make more sense to have, as an enhancement, a way to add the 64-bit OS condition on top of what prerequisites already require, or instead a way to install either a 32-bit or a 64-bit version of the MSI as part of the same setup.exe file?
This 64-bit setup.exe request stems from this Microsoft article: http://msdn.microsoft.com/en-us/library/aa372396%28v=VS.85%29.aspx where it says "When using a bootstrapping application to install a 64-bit Windows Installer Package, compile the bootstrapping application as a 64-bit application." It's obviously not a requirement, rather a guideline. Some of the prerequisites in my setup are for both my 32-bit release and 64-bit release, so I don't condition them for a specific architecture and thus, they get installed when doing a silent installation.
I would say it makes more sense to add a way to install either a 32-bit or a 64-bit version of the MSI as part of the same setup.exe. However, there may be customers who want to install 32-bit on a 64-bit machine for whatever reason. So maybe there could be an option in IS that, if turned on, would display a message to the end-user running on a 64-bit machine asking if they would like to install the 32-bit version or the 64-bit version. If the option is turned off, the 64-bit version gets installed by default.
