Question regarding compiling React Native under different directories

[kzlar]

Hello,

I'm using Expo (eas build --local) to build React Native apps. Expo and RN has "built in" support for ccache which seems to work well when compiling under the same directory. However, building under different directories, which is what happens when using eas build --local does not seem to work (everything is a cache miss on the 2nd run).

I've tried setting CCACHE_NOHASHDIR=true and CCACHE_BASEDIR=${EAS_BUILD_WORKINGDIR} (which is the temporary directory created for each build), and followed the logfile and can make the following observations when comparing Command line lines and Executing lines:

1. "common"/"simple" flags do seem to be rewritten correctly. e.g. -I or -F, object files etc.
2. "newer" flags seem to not be rewritten. For example -ivfsoverlay <EAS_BUILD_WORKINGDIR>/some/path stays exactly the same in the Executing line. The config file does set sloppiness=...,ivfsoverlay,... so I assume that is removed from the hash calculations? Another examples are -fmodules-cache-path and -fmodules-cache-path which are not rewritten, while modules is in the sloppiness config line, it's not clear if that's ignored or not? And there's also -fbuild-session-file which is not rewritten.

Am I looking in the right place when trying to understand those cache misses?
Is all of the above expected to work and it's a config issue on my end or is what I'm seeing a bug/not-supported?

Thanks!

[jrosdahl]

The config file does set sloppiness=...,ivfsoverlay,... so I assume that is removed from the hash calculations?

No, the only thing "ivfsoverlay sloppiness" currently does is to just allow -ivfsoverlay (see #839 / 97f42b9). It would be easy to make ccache rewrite the path into relative.

Another examples are -fmodules-cache-path and -fmodules-cache-path which are not rewritten, while modules is in the sloppiness config line, it's not clear if that's ignored or not?

Ccache does not know about -fmodules-cache-path (and neither do I), so it's not ignored.

And there's also -fbuild-session-file which is not rewritten.

Same thing here.

Am I looking in the right place when trying to understand those cache misses?

Yes. To dig even deeper you can enable the debug mode as described in Cache debugging to know exactly why you get cache misses.

Is all of the above expected to work and it's a config issue on my end or is what I'm seeing a bug/not-supported?

What you're seeing is simply ccache not knowing about those options because nobody has investigated them in a ccache context before.

[kzlar]

Hi @jrosdahl and thank you for your reply!
All of the above makes sense. I can attempt to come up with a PR that handle these options, will circle back here when I have it and hopefully it could be merged :)

[kzlar]

Opened a PR: #1567
Still in draft as I'm running some more tests, but would appreciate your feedback.