ccache/ninja does not work when switching branches.

[zhxinyu]

Version

v21.0.0-pre

Platform

Darwin Siri-Pro.local 21.6.0 Darwin Kernel Version 21.6.0: Wed Aug 10 14:25:27 PDT 2022; root:xnu-8020.141.5~2/RELEASE_X86_64 x86_64

Subsystem

No response

What steps will reproduce the bug?

No response

How often does it reproduce? Is there a required condition?

No response

What is the expected behavior? Why is that the expected behavior?

No response

What do you see instead?

As suggested in the building.md, we should have near instantaneous build even when switching branches.

However, when I switched the branch in my local, I can see that it restarted the building process for make.

<username>@<hostname> node % git checkout main
Switched to branch 'main'
Your branch is up to date with 'origin/main'.
<username>@<hostname> node % make
+ exec ./configure --ninja
Node.js configure: Found Python 3.10.13...
INFO: configure completed successfully
ninja -C out/Release  
ninja: Entering directory `out/Release'
[3/3914] CC obj/deps/v8/third_party/zlib/v8_zlib.cpu_features.o

Additional information

No response

[aduh95]

Why is that the expected behavior?

[zhxinyu]

The expected behavior should be we should have near instantaneous build even when switching branches.
As suggested in the building.md file.

[joyeecheung]

Hmm, I don’t think make is supposed to use ninja by default unless you set BUIlD_WITH=ninja in the environment. But I think I have been able to use ccache + ninja just fine most of the time unless deps/v8 gets updated (in particular, the headers, because V8 is just structured in a way that any changes to the headers could lead to almost a rebuild) have you checked if deps/v8 is changed when you switch branches?

[joyeecheung]

Also I think building.md is a bit misleading here - ccache only helps you when switching between branches that aren’t very different from each other and when the differences themselves would not result in a rebuild. If, for example, a header that most files depend on gets changed, ccache cannot help because you just have to rebuild to see the changes to take effect.

[legendecas]

ccache helps in condition like switching between branches back and forth, as the previous compilation results have been cached. I believe the words in the document can be improved.