Updating the various windows build scripts to have a comment explaining the VS version selection logic.

1 files changed, 14 insertions, 0 deletions

diff --git a/build.cmd b/build.cmd
index 90418a0614..eb734e3663 100644
--- a/build.cmd
+++ b/build.cmd
@@ -5,6 +5,20 @@ echo Starting Build at %TIME%
 set __ThisScriptFull="%~f0"
 
 :: Default to highest Visual Studio version available
+::
+:: For VS2015 (and prior), only a single instance is allowed to be installed on a box
+:: and VS140COMNTOOLS is set as a global environment variable by the installer. This
+:: allows users to locate where the instance of VS2015 is installed.
+::
+:: For VS2017, multiple instances can be installed on the same box SxS and VS150COMNTOOLS
+:: is no longer set as a global environment variable and is instead only set if the user
+:: has launched the VS2017 Developer Command Prompt.
+::
+:: Following this logic, we will default to the VS2017 toolset if VS150COMNTOOLS tools is
+:: set, as this indicates the user is running from the VS2017 Developer Command Prompt and
+:: is already configured to use that toolset. Otherwise, we will fallback to using the VS2015
+:: toolset if it is installed. Finally, we will fail the script if no supported VS instance
+:: can be found.
 if defined VS150COMNTOOLS (
   set "__VSToolsRoot=%VS150COMNTOOLS%"
   set "__VCToolsRoot=%VS150COMNTOOLS%\..\..\VC\Auxiliary\Build"