Kdesu does not define the required feature macros for the functions it uses. It builds on glibc (by accident, since the *glibc* man pages specify those macros), but does not build on musl.
Have you filed a bug upstream about this?
Created attachment 412294 [details, diff] Proposed patch for ::musl Add the needed feature macros.
(In reply to Manuel Rüger from comment #1) > Have you filed a bug upstream about this? No, not yet. I've added a patch for the musl overlay, which collects musl-related issues. I'll notify upstream.
Since you have a patch, better to go straight to reviewboard: http://git.reviewboard.kde.org/
(In reply to Wiktor W Brodlo from comment #3) > (In reply to Manuel Rüger from comment #1) > > Have you filed a bug upstream about this? > > No, not yet. I've added a patch for the musl overlay, which collects > musl-related issues. I'll notify upstream. What is the status here?
(In reply to Johannes Huber from comment #5) > What is the status here? I've posted a more correct patch to the upstream reviewboard[0]. Until it gets merged into upstream, I'm posting an updated patch that adds kdesu-5.19.0 to ::musl below. [0] https://git.reviewboard.kde.org/r/127415/
Created attachment 428478 [details, diff] Add kdesu-5.19.0 to ::musl
The patch has been accepted upstream.
Confirmed by upstream
https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=0fdba172a462e9a22ad68966522b22c40bd82e72