Sigaction

pub const Sigaction = switch (native_os) {
    .linux => switch (native_arch) {
        .mips,
        .mipsel,
        .mips64,
        .mips64el,
        => if (builtin.target.abi.isMusl())
            common_linux_Sigaction
        else if (builtin.target.ptrBitWidth() == 64) extern struct {
            pub const handler_fn = *align(1) const fn (SIG) callconv(.c) void;
            pub const sigaction_fn = *const fn (SIG, *const siginfo_t, ?*anyopaque) callconv(.c) void;

            flags: c_uint,
            handler: extern union {
                handler: ?handler_fn,
                sigaction: ?sigaction_fn,
            },
            mask: sigset_t,
            restorer: ?*const fn () callconv(.c) void = null,
        } else extern struct {
            pub const handler_fn = *align(1) const fn (SIG) callconv(.c) void;
            pub const sigaction_fn = *const fn (SIG, *const siginfo_t, ?*anyopaque) callconv(.c) void;

            flags: c_uint,
            handler: extern union {
                handler: ?handler_fn,
                sigaction: ?sigaction_fn,
            },
            mask: sigset_t,
            restorer: ?*const fn () callconv(.c) void = null,
            __resv: [1]c_int = .{0},
        },
        .s390x => if (builtin.abi == .gnu) extern struct {
            pub const handler_fn = *align(1) const fn (SIG) callconv(.c) void;
            pub const sigaction_fn = *const fn (SIG, *const siginfo_t, ?*anyopaque) callconv(.c) void;

            handler: extern union {
                handler: ?handler_fn,
                sigaction: ?sigaction_fn,
            },
            __glibc_reserved0: c_int = 0,
            flags: c_uint,
            restorer: ?*const fn () callconv(.c) void = null,
            mask: sigset_t,
        } else common_linux_Sigaction,
        else => common_linux_Sigaction,
    },
    .emscripten => emscripten.Sigaction,
    .netbsd, .driverkit, .ios, .maccatalyst, .macos, .tvos, .visionos, .watchos => extern struct {
        pub const handler_fn = *align(1) const fn (SIG) callconv(.c) void;
        pub const sigaction_fn = *const fn (SIG, *const siginfo_t, ?*anyopaque) callconv(.c) void;

        handler: extern union {
            handler: ?handler_fn,
            sigaction: ?sigaction_fn,
        },
        mask: sigset_t,
        flags: c_uint,
    },
    .dragonfly, .freebsd => extern struct {
        pub const handler_fn = *align(1) const fn (SIG) callconv(.c) void;
        pub const sigaction_fn = *const fn (SIG, *const siginfo_t, ?*anyopaque) callconv(.c) void;

        /// signal handler
        handler: extern union {
            handler: ?handler_fn,
            sigaction: ?sigaction_fn,
        },
        /// see signal options
        flags: c_uint,
        /// signal mask to apply
        mask: sigset_t,
    },
    .illumos => extern struct {
        pub const handler_fn = *align(1) const fn (SIG) callconv(.c) void;
        pub const sigaction_fn = *const fn (SIG, *const siginfo_t, ?*anyopaque) callconv(.c) void;

        /// signal options
        flags: c_uint,
        /// signal handler
        handler: extern union {
            handler: ?handler_fn,
            sigaction: ?sigaction_fn,
        },
        /// signal mask to apply
        mask: sigset_t,
    },
    .haiku => extern struct {
        pub const handler_fn = *align(1) const fn (SIG) callconv(.c) void;
        pub const sigaction_fn = *const fn (SIG, *const siginfo_t, ?*anyopaque) callconv(.c) void;

        /// signal handler
        handler: extern union {
            handler: ?handler_fn,
            sigaction: ?sigaction_fn,
        },

        /// signal mask to apply
        mask: sigset_t,

        /// see signal options
        flags: i32,

        /// will be passed to the signal handler, BeOS extension
        userdata: *allowzero anyopaque = undefined,
    },
    .openbsd => extern struct {
        pub const handler_fn = *align(1) const fn (SIG) callconv(.c) void;
        pub const sigaction_fn = *const fn (SIG, *const siginfo_t, ?*anyopaque) callconv(.c) void;

        /// signal handler
        handler: extern union {
            handler: ?handler_fn,
            sigaction: ?sigaction_fn,
        },
        /// signal mask to apply
        mask: sigset_t,
        /// signal options
        flags: c_uint,
    },
    // https://github.com/SerenityOS/serenity/blob/ec492a1a0819e6239ea44156825c4ee7234ca3db/Kernel/API/POSIX/signal.h#L39-L46
    .serenity => extern struct {
        pub const handler_fn = *align(1) const fn (SIG) callconv(.c) void;
        pub const sigaction_fn = *const fn (SIG, *const siginfo_t, ?*anyopaque) callconv(.c) void;

        handler: extern union {
            handler: ?handler_fn,
            sigaction: ?sigaction_fn,
        },
        mask: sigset_t,
        flags: c_uint,
    },
    else => void,
}