Please do note that _XOPEN_SOURCE must be 600 and not 700 because some components of KDE still use rindex which is no longer supported in X/Open 7.

As I mentioned on the KDE bug, there is a possibility that changes like this would break FreeBSD. FreeBSD operates by a model of exporting symbols by default for legacy/BSD-specific needs. However if a feature flag is set, it limits its exports to *only* that required by the feature flag. Notably, all BSD-specific exports are removed in FreeBSD if you set a feature flag that doesn't also standardize that BSD feature, and unlike C libraries like musl and glibc, they don't support any feature flags to specifically request BSD-specific exports be exported.

See KIO commit 15451d505fdbc37b5d027f8ad1ba6aeb6314cc2d and D6597 for an example of where I had to take special pains when committing musl-specific fixes to KF5 to avoid breaking FreeBSD.

Andrew, have you been able to test your patches on a FreeBSD at all? We can catch it in CI now, but on the other hand I have already tried to fix this by pushing feature flag defines into source repositories requiring the extra defines rather than making it a KDE-wide define. I had previously verified that these fixes allowed all of KF5 (though not all of Plasma5) to build on Alpine Linux, though it's been a month since I had reverified that.

(BTW where is rindex being used? lxr says only in ksysguard's FreeBSD and IRIX files, surely that's not the issue?)

rindex was being used in kscreenlocker but that code was removed last year.

Let's push this then ;)

You don't seem to have a developer account? I can push this but I need your email address for the git authorship.

Ah, found it in bugzilla :-)

This change appears to have resulted in a severe regression of builds on FreeBSD.
Any ideas?

Indeed,

22:23:51 In file included from /usr/include/sys/mount.h:36:
22:23:51 /usr/include/sys/ucred.h:84:2: error: unknown type name 'u_int'; did you mean 'uint'?
22:23:51 u_int cr_version; /* structure layout version */
22:23:51 ^

https://build.kde.org/view/Frameworks/job/Frameworks%20kcoreaddons%20kf5-qt5%20FreeBSDQt5.11/5/console

I'll revert.

Sorry, if I'd been able to check this earlier I'd have warned against pushing, this was the kind of concern I was addressing with my earlier comment about FreeBSD. I had run into a lot of those issues when trying to get KF5 to build on Alpine.

Adding an _XOPEN_SOURCE or similar define will in general require a lot of porting effort to remove things like obsolete type names, BSD-specific extensions, functions used in later standards than the one we adopt, etc.

It was easier for me to make fixes per-Framework than to try to get everything to compile under an _XOPEN_SOURCE setting, but it may be better as a long-term concern to standardize on something and then do the one-time cost to make sure everything still builds. Certainly I think we don't want to continue to rely implicitly on glibc forever given the expansion of other form factors that use alternate libc's.