Some language runtimes create threads before the application main() function is executed. Even if Linux has to retain bug-for-bug ABI compatibility there is val

Some language runtimes create threads before the application main() function is executed. Even if Linux has to retain bug-for-bug ABI compatibility there is valid reason to only provide fucked up the setid() syscalls. The problem is even worse than it looks at first glance because setid() can fail per thread and there is no sane way to recover from this in userspace. Atomic syscalls are the only sane API for this and Linux is lacking those.