Determining the last changelist synced to in Perforce

Question

A question that occasionally arises is what is the best way to determine the changelist that you last synced to in Perforce. This is often needed for things like injecting the c

Answer 1

For a serious build (one that is being prepared for testing), explicitly specify the desired label or changelist number, sync to label, and imbed it in build artifacts.

If a changelist (or label) is not given, use p4 counter change to get the current change number, and record it. But you still need to sync everything using that change number.

I don't think you can achieve exactly what you want, because in general, an entire workspace isn't synced to a particular changelist number. One can explicitly sync some files to older revisions, and then a single changelist number is meaningless. That's why a fresh sync is required to ensure that a single changelist number accurately represents the code version.

---

Regarding the comments: Yes, my answer is intended for use by configuration managers preparing a build to give to QA. Our developers don't normally sync as part of a build; they do a build prior to submitting—so that they can make sure their changes don't break the build or tests. In that context, we don't bother to embed a repository label.

With your approach, you are making the assumption that your whole workspace was synced to head at the time of your last changelist submission, and that changelist included all of your open files. It's too easy to be mistaken in those assumptions, hard to detect, and horribly expensive in terms of lost time. On the other hand, solving the problem is easy, with no drawbacks. And because a changelist number can be explicitly specified, it doesn't matter what revision you need or how quickly the codebase is changing.