For reasons related to customers with different applications versions i need to maintain in my laptop several versions of Delphi (7, XE 7, XE 8, XE 10.1 Berlin and XE 10.2 Tokyo). My main concern is about PATH variable and problems during compilation and linking time. There'll be any problems ? Do i need to change what ? Any suggestion is most welcome.
I have all versions of Delphi from 7 thru XE8 installed in a single VM and versions 1 thru 6 in another (my Delphi "museum" :)).
The Delphi "museum" is a Windows XP VM to avoid the problems that those older versions of Delphi have with more recent Windows versions. The Delphi 7+ VM started life as Windows 7 VM but has since been upgraded to Windows 8.x and then Windows 10 without any problem.
The two sets of VM's are kept separate in this way to avoid OS complications with those older versions and because I use 1-6 only very, very rarely and version 7+ more often. The precise version at which the "cut-off" was made was determined by the fact that dotted unit names were also only supported from version 7 onward so a lot of the code I ever wrote for 7+ is simply not even usable with 1-6 so there's no point having them alongside each other.
In both cases the IDE/compilers (any version) have no intrinsic problems running alongside other versions.
The only real difficulty is installing Delphi 2006 on Windows Vista (or later). Should you ever need to, this is the only one that presents any real difficulty due to a dependency on .NET which is not handled very well by the installer. But it is do-able and not especially difficult as long as you follow the steps described in detail by Dr. Bob.
With a large number of Delphi versions installed the overall length of the PATH variable can become a problem, but in my experience this is a problem only of manageability. To simplify things on that score and to avoid problems with earlier versions of Delphi on more recent versions of Windows, I installed all my IDE's in a sub-folder directly off the root:
c:\delphi\<version>
Where version is each Delphi version number (e.g. 7.0, 2007, 2009, XE, XE2 etc etc). I then have a number of other folders for shared components:
c:\delphi\bde
c:\delphi\database desktop
c:\delphi\shared files
When I setup the VM I installed each Delphi version in order and changed the installation locations for these components to these locations. In this way there is one common installation of these shared components which is updated by each more recent version as required.
I also have a c:\delphi\common\ folder where I keep things such as pre-compiled FastMM_FullDebugMode.dll etc to be shared across all Delphi versions.
I did all this primarily for my own benefit however, to keep things organised and consistent rather than to solve any particular problem (apart from the previously mentioned issues affecting older versions if installed under Program Files).
e.g. if you simply install into default locations then you will end up with versions "scattered" across Borland, CodeGear and Embarcadero folders. All my IDE versions are in one place.
With or without these considerations, the IDE should be perfectly happy to run all the different versions you mention without any particular configuration required, but you may need to pay attention to configuration/assumptions made by some 3rd party packages/libraries.
Most 3rd party libraries/packages are usually fine, but there may be the occasional one that needs a bit of help. I myself have never come across anything that couldn't be resolved but have to say that I also don't use 3rd party libraries particularly extensively so simply may not have come across any "trouble makers".
In any event, it's unfortunately difficult to give general advice on this point since it obviously depends very much on the 3rd party libraries and the particular "problems" that any particular one might have.