SIGRTMIN and SIGRTMIN+1 previous sigaction are being silently ignored when set by crt_constructor

[dlangBugzillaToGithub]

Luís Ferreira reported this on 2024-09-09T18:09:24Z

Transferred from https://issues.dlang.org/show_bug.cgi?id=24756

Description

Libraries that implement crt0 constructor (crt_constructor) that set SIGRTMIN and SIGRTMIN+1 get silently ignored after runtime initialisation as it overrides without checking sigaction previous assignments.

As specified by POSIX, this should be checked and SIGRTMIN+n should have runtime checks, and not hardcoded.

Runtime, at bare minimum, should assert when silently trying to override a previous sigaction.