Reducing Visual Studio Installations with Toolchains

07.03.2024 Miłosz Kosobucki No comments

If you work on C++ projects on Windows that need to be built with multiple Visual Studio C++ compiler versions, you need some way to manage the installations of all these build environments. Either you have multiple IDEs installed, or you know about build tools (https://aka.ms/vs/17/release/vs_BuildTools.exe) and maybe keep only the latest full VS IDE plus older Build Tools.

However, it turns out that you can have just the latest IDE but with multiple toolchains installed for older compiler targets. You won’t even need the Build Tools.

To use these toolchains you need to install them in your chosen VS installation and then call vcvarsall.bat with an appropriate parameter.

You can even have no IDE installed if you don’t need it but only the Build Tools with the required toolchains. That’s useful when you use a different IDE like JetBrains Clion or Visual Studio Code. Note, however, that to be license- compliant, you still need a valid Visual Studio subscription.

Installing the toolchain

1. Go to the Visual Studio Installer and click “Modify” on your main VS version (2022 in my case).
2. Go to “Individual components” and search for the appropriate toolchain. For example, to get the latest VS2019 C++ compiler in VS 2022 installer, you need to look at this:How do you know that 14.29 corresponds to VS 2019? Well, you have to consult this table: https://en.wikipedia.org/wiki/Microsoft_Visual_C%2B%2B#Internal_version_numbering – look at the “runtime library version” column as that’s the C++ compiler version really.
3. Finish the installation of the desired components.

Setting up the environment from cmd.exe

The only thing you need to do to start with a different toolchain is to pass an option to your vcvarsall.bat invocation:

C:\Users\mikom>"c:\Program Files\Microsoft Visual Studio\2022\Professional\VC\Auxiliary\Build\vcvarsall.bat" -vcvars_ver=14.29

With such a call, I get a shell where cl.exe indeed uses the VS2019 compiler variant:

As you can see, I called vcvarsall.bat from VS2022 yet I got VS2019 variant of the compiler For more info about vcvarsall.bat see: https://learn.microsoft.com/en-us/cpp/build/building-on-the-command-line.

Setting up the environment for PowerShell

If you do your compilation in Powershell, vcvarsall.bat is not very helpful. It will spawn an underlying cmd.exe, set the necessary env vars inside it, and close it without altering your PowerShell environment.

(You may try to do some hacks of printing the environment in the child cmd.exe and adopting it to your Pwsh shell, but that’s a hack).

For setting up a development environment from PowerShell, Microsoft introduced a PowerShell module that does just that.

To get it, you first have to load the module:

Import-Module "C:\Program Files\Microsoft Visual Studio\2022\Professional\Common7\Tools\Microsoft.VisualStudio.DevShell.dll"

And then call the Enter-VsDevShell cmdlet with appropriate parameters:

Enter-VsDevShell -VsInstallPath 'C:\Program Files\Microsoft Visual Studio\2022\Professional\' -DevCmdArguments "-vcvars_ver=14.29" -Arch amd64 -SkipAutomaticLocation

This cmdlet internally passes arguments to vcvarsall.bat so you specify the toolchain version as above.

With this invocation, you get your desired cl.exe compiler:

For more info about Powershell DevShell module see: https://learn.microsoft.com/en-us/visualstudio/ide/reference/command-prompt-powershell

Setting up Qt Creator Kit with a toolchain

Unfortunately, Qt Creator doesn’t detect the toolchains in a single Visual Studio installation as multiple kits. You have to configure the compiler and the kit yourself:

I am a script, how do I know where Visual Studio is installed?

If you want to query the system for VS installation path programatically (to find either vcvarsall.bat or the DevShell PowerShell module) you can use the vswhere tool (https://github.com/microsoft/vswhere).

It’s a small-ish (0.5MB) self-contained .exe so you can just drop it in your repository and don’t care if it’s in the system. You can also install it with winget:

winget install vswhere 

It queries the well-known registry entries and does some other magic to find out what Visual Studio installations your machine has.

By default it looks for the latest version of Visual Studio available and returns easily parseable key:value pairs with various infos about the installation. Most notably, the installation path in installationPath.

It also has various querying capabilities, like showing only the VS installation that have the C++ workload installed.

For example, to get the installation path of the newest Visual Studio with C++ workload, you call:

vswhere -latest -products * -requires Microsoft.VisualStudio.Component.VC.Tools.x86.x64 -property installationPath

Caveats

I haven’t found an easy way to query vcvarsall for something along the lines “give me the latest available toolchain in a given VS product line (2019, 2022 etc.)”. So if you call an explicit version (like 14.29) and a newer one appears, you will still be looking for the older one. However:

• When vcvarsall.bat is called without any toolchain parameter (vcvars_ver), it defaults to itself so you may assume that it’s the latest one in this installation folder.
• Microsoft seems to stop bumping the relevant part of the version of the Visual Studio C++ compiler once the next version of VS is out. So for example it seems that 14.29 will be a proper target for VS2019 C++ compiler until the end of time.