How to use ccache with vcpkg

[xiaozhuai]

I upgrade my ports everyday, which waste a lot of time.
It's there any tricks that I can use ccache on building vcpkg ports? (I use macos and windows msvc)
This will help me a lot. Thanks!

[klalumiere]

I've just tried and it works (I tried with sccache but it shouln't change anything). 🎉 You need to set the environment variable CMAKE_<LANG>_COMPILER_LAUNCHER to ccache, and if you are on Windows, you'll probably need to set VCPKG_KEEP_ENV_VARS too.

On Linux, my whole command line looked like

CMAKE_CXX_COMPILER_LAUNCHER=sccache CMAKE_C_COMPILER_LAUNCHER=sccache  VCPKG_BINARY_SOURCES=clear cmake -B build2 -S .

(as you can see, I set my environment variable inline). You can use ccache --show-stats to ensure it's working.

[dg0yt]

These variables are specifc to CMake. I doubt they reach port which use other build systems.
vcpkg does forward CMAKE_<lang>_COMPILER for many build systems. So it might be more promising to make that variable point to a wrapper which launches the compiler via ccache.

[Tagman]

I had the experience that you might need to rebuild your toolchain for the changes to take effect.

[Tagman]

Sure. When using the manifest mode (having a vcpkg.json file in your project and running cmake with -DCMAKE_TOOLCHAIN_FILE=), you need to:

• remove the vcpkg_installed folder from your build directory.
• remove packages folder from your vcpkg directory
• remove buildtrees folder from vcpkg directory (just to be sure)
• remove archives directory from %LOCALAPPDATA%/vcpkg

This might be a bit overkill, but will lead to all your dependencies being rebuilt. If you are using the classic mode (e.g. calling vcpkg.exe install ...) you need to remove the vcpkg_installed directory from your vcpkg directory.

I hope this helps. Feel free to ask if it doesn't. :)

[dg0yt]

I don't understand why you would want to force a rebuild of installed binary artifacts to enable the use of ccache. Maybe that's the answer to a different type of problem?

[xiaozhuai]

I don't understand why you would want to force a rebuild of installed binary artifacts to enable the use of ccache.

Because ccache cause vcpkg binary caching expired, I guess.

[dg0yt]

I don't understand why you would want to force a rebuild of installed binary artifacts to enable the use of ccache.

Because ccache cause vcpkg binary caching expired, I guess.

This doesn't really anwer why one should remove everything, manually.
Without knowing the actual problem, it doesn't make sense to suggest such radical measures.

[Tagman]

I don't understand why you would want to force a rebuild of installed binary artifacts to enable the use of ccache. Maybe that's the answer to a different type of problem?

When I was trying to get ccache to work, I had no hits whenever I was just rebuilding the project. I had to remove my complete build folder. This was a 1-2hr try like 4 months ago, not sure if all that was really necessary.

I agree with you, it's radical, but its not the end of the world to do a rebuild of your toolchain and project. But it also might not lead to success. I was trying to use ccache with vcpkg and in my actual project. For now I skipped solving the problem as time is short. But it will pop up again in some weeks, so hopefully I can give you an explanation and solution.

[congzhangzh]

@xiaozhuai the follow way may work for some vcpkg port, some other failed!

Use the wrapper and set CC/CXX, don’t forget to make CC/CXX keep

https://github.com/congzhangzh/daily-scripts-4-us/tree/main#2-three-way-to-make-ccache-work-on-windows

https://learn.microsoft.com/en-us/vcpkg/users/config-environment#vcpkg_keep_env_vars

[tsondergaard]

I've created #37689.