`incremental = true` as the default in config.toml?

[anp]

I'm curious whether it would make sense for incremental = true to be the default for rustbuild in the absence of another setting.

Per @eddyb on IRC:

07:53 <eddyb> it used to be bad for a bit until a few months ago (that is, it would produce a very slow compiler) but nowadays we should just turn it on by default lol
07:53 <eddyb> (feel free to open an issue about it)
07:53 <eddyb> it would need to not be turned on for {stable,beta,nightly} builds (as opposed to regular dev builds), but idk how that's handled (I assume it's still possible to make that distinction)

Searching around for incremental-related compiler perf issues it does seem to me that most of them are closed.

[eddyb]

cc @Mark-Simulacrum

[Mark-Simulacrum]

We can definitely make incremental the default and just switch it off on any build configured with a non-dev channel. I think that's all CI, not sure, can confirm.

[jyn514]

I tried adding this in #76417 and it was closed for various reasons:

• It sometimes breaks.
• It takes about 5GB of extra disk space, which might be too much for some people.
• It often causes 32-bit builds on Windows to fail because rustc needs more memory with incemental objects.

With those in mind does this still make sense to change? If not, I think this should be closed.

[pierwill]

incremental = true is suggested in the dev guide. It might make sense to call this out more prominently there. @jyn514 it does feel like this can be closed. :)

[pierwill]

That being said, there does appear to be popular demand for incremental by default. 😇

[jyn514]

Since #77004, this is enabled by default for the compiler and library profiles.