Github actions and C++ precompiled headers

[soerlemans]

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Question

What GitHub Actions topic or product is this about?

Actions Cache

Discussion Details

Anybody have any idea if precompiled headers play nicely with github-actions?
My project is becoming quite large so I started precompiling STL headers.
And I am now wondering if precompiled headers can be cached and or restored without causing a rebuild?

As I want to save time recompiling STL, library headers and or project headers that dont change often.
But it seems the only way might be to touch update my pch headers? (which seems dangerous and hacky)

Similar issue:
actions/checkout#364

Git on filetime modifications.
https://archive.kernel.org/oldwiki/git.wiki.kernel.org/index.php/Git_FAQ.html#Why_isn.27t_Git_preserving_modification_time_on_files.3F

Running build:
https://github.com/soerlemans/crowlang/actions/runs/20696612853/job/59412823406?pr=72

My workflow file:
https://github.com/soerlemans/crowlang/blob/feature/pointers/.github/workflows/unit-tests.yml

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[DeveloperVaibhav1]

Yes, precompiled headers (PCH) can work with GitHub Actions caching, but it depends on how stable your build environment is. If the compiler version, flags, or dependencies change, the cached PCH may become invalid and force a rebuild.

A common approach is to include the compiler version and build configuration in the cache key. For example:

• compiler version
• OS
• hash of relevant header files

This helps ensure the cache is only restored when the environment is compatible.

However, because PCH files are sensitive to small changes, many projects still end up rebuilding them frequently. In some cases using tools like ccache or sccache with GitHub Actions can give more reliable build speed improvements than caching PCH d