Fix WIN32 CMake versioning

[feynmanliang]

Description

CMake build is erroring out on Windows because OBS_VERSION is not set:

Selecting Windows SDK version 10.0.19041.0 to target Windows 10.0.20190.
OBS_VERSION: 
CMake Error at CMakeLists.txt:85 (string):
  string sub-command REPLACE requires at least four arguments.


CMake Error at CMakeLists.txt:89 (list):
  list index: 1 out of range (-1, 0)


CMake Error at CMakeLists.txt:90 (list):
  list index: 2 out of range (-1, 0)

Motivation and Context

This defaults it to something sane to fix it.

How Has This Been Tested?

configure and generate from cmake-gui

Tested on CMake 3.18.2

Types of changes

Code cleanup (non-breaking change which makes code smaller or more readable)

Checklist:

• My code has been run through clang-format.
• I have read the contributing document.
• My code is not on the master branch.
• The code has been tested.
• All commit messages are properly formatted and commits squashed where appropriate.
• I have included updates to all appropriate documentation.

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This change is 

[RytoEX]

The OBS_VERSION variable should already be set in cmake/Modules/ObsCpack.cmake line 25 for normal builds. Under what conditions are you encountering this error? This is the first time I've heard of this occurring.

[WizardCM]

This occurs when git is not in your path. I would vote for a more informative error. "Git not found in PATH, so the OBS version could not be set. Either fix this issue, or manually set OBS_VERSION_OVERRIDE"

[feynmanliang]

Thanks for pointing me to that; this problem occurred because I cloned the repo using WSL's git but attempted to build using CMake in Windows. The .git directory is present (resulting the first conditional branch to execute), but the execute_process(... git describe...) returns empty because it is not on the Windows path.

I added message(STATUS "OBS_VERSION=${OBS_VERSION}") to confirm and got the output:

Selecting Windows SDK version 10.0.19041.0 to target Windows 10.0.20190.
OBS_VERSION=

I can confirm manually setting OBS_VERSION as a CMake variable does not fix the issue; it is overridden by the execute_process back to empty string.

Since it defaults to CPACK_PACKAGE_VERSION already in the case .git is not found, would we be okay with setting a sane default for OBS_VERSION when OBS_VERSION remains empty after attempting to set it by executing git? The format of CPACK_PACKAGE_VERSION is not quite what is expected in the WIN32 build (it's splitting on a "-" in https://github.com/obsproject/obs-studio/blob/master/CMakeLists.txt#L85 which is absent in CPACK_PACKAGE_VERSION), but I am happy to change the default to just append that from CPACK_PACKAGE_VERSION.

[WizardCM]

Ah my bad, you need to manually set OBS_VERSION_OVERRIDE. I always forget about that one.

[feynmanliang]

Yep that works; this could be as simple as a readme update then :) How does that sound?

[WizardCM]

That's certainly an option, but I think having CMake report an accurate error would be handy too.

[feynmanliang]

Will do both

[feynmanliang]

OK, I just made the CPACK_PACKAGE_VERSION default apply when the `git` subprocess call returns empty.

…

On Thu, Aug 20, 2020 at 4:42 PM Matt Gajownik ***@***.***> wrote: That's certainly an option, but I think having CMake report an accurate error would be handy too. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#3300 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAHRW5MFMRLDKPRK6TYCDG3SBWYFVANCNFSM4QGTFR7Q> .

[WizardCM]

Closing this PR in favour of #4377 which was merged for 27.0 a while back.