Copy (1) and edit (2) both bump mtime, usually. It's not obvious that in the workflow you describe ninja is problematic, rather than the workflow itself (which is atypical).

▲

usefulcat 5 hours ago | parent | next [-]

> 3) move the copy to it's original location

Copy and edit do, but move (aka rename) generally does not, and that is the part that is problematic.

I don't think the described sequence of operations is all that unusual. Not the most common case for sure, but hardly unlikely in the grand scheme of things.

▲

mizmar 6 hours ago | parent | prev [-]

ninja fails to detect that file changed from last build - all it's mtime, ctime, inode and size can change, yet it's not detected as long as mtime is not newer than target.

▲

loeg 6 hours ago | parent [-]

Again, this is just a weird workflow, and you're assuming copy/edit don't bump mtime. That usually isn't the case. If you're doing this weird thing, you can just run `touch` when you move files over existing files like this to explicitly bump mtime.

	▲	MereInterest 5 hours ago \| parent \| next [-]
		I run into this issue when building against different environments, each with a 1. A library depends on a system package. To test against the different versions of the system package, the library is compiled within a container. 2. To minimize the incremental rebuild time, the `build` directory is mounted into the build container. Even when using a different version of the system package, this allows re-use of system-independent portions of the build. 3. When switching to a build container with a different version of the system package, the mtime of the system package is that of its compilation, not that of the build container's initialization. Therefore, the library is erroneously considered up-to-date. Because the mtime is the only field checked to see if the library is up to date, I need to choose between having larger disk footprint (separate `build` directory for each build container), slower builds (touch the system package on entering the container, forcing a rebuild), or less safe incremental builds (shared `build` directory, manually touch files when necessary).
	▲	mizmar 5 hours ago \| parent \| prev [-]
		>you're assuming copy/edit don't bump mtime Incorrect, I only assume move/rename of backup to original location doesn't change it's mtime (which it doesn't with default flags or from IDE or file manager). And I don't think this is a weird or obscure workflow, I do it all the time - have two versions of a file or make a backup before some experimental changes, and restore it later.