os/signal: No access to the siginfo_t struct

[quentinmit]

The siginfo_t struct that is delivered with signals contains various useful information about the signal. In some cases, this information is necessary to implement the kernel API of various features. For example, fcntl(F_SETLEASE) requires that your process receive a SIGIO when the lock is broken, and the si_fd field in the siginfo_t struct tells you what filehandle the kernel is notifying your process about.

Please provide an interface that will allow Go code to access the information in the siginfo_t struct.

[rsc]

We'd need to figure out a nice, portable API to do this.

[dothebart]

https://man7.org/linux/man-pages/man2/sigaction.2.html is the referenced Structure.
Since its quiet usefull for debugging to log i.e. which process sent you a signal, it would be really great to see support for this.

[ianlancetaylor]

The stress here is on portable. The man page you cite is Linux-specific.

[LordRusk]

Rather than needing a super portable way to do this, could we simply add access to it through /x/sys/unix because of its specificity? It's really dragging down a project of mine to not have access to this struct in any way.

[ianlancetaylor]

We still need a nice, portable API. I don't see how using x/sys/unix helps. I don't have any ideas for an API.

[LordRusk]

Please correct me if I'm mistaken, but it seems the SignalfdSigInfo struct is equivalent to siginfo_t - only missing a few fields, including si_sigval which is what I need. Syscall is deprecated in favor of /x/sys for OS specificity, that is why I bring it up. Not sure why si_sigval wasn't included, or what it would take to add it, but with this in mind I'm not sure why we'd need a 'portable API' for this.

/x/sys/unix/.SignalfdInfo & siginfo_t comparison

[ianlancetaylor]

I agree what we don't need a portable API for the exact definition of siginfo_t. We can do something similar to how fs.FileInfo has a Sys method that returns a system-specific data structure.

What we need is a portable API for how to access that system-specific information.

[LordRusk]

SignalfdSiginfo is not an equivalent of siginfo_t and isn't supposed to be, that's my bad.