Fix the definition of sigevent on FreeBSD and Linux

It was originally defined back before rust could represent C unions.  So
instead of defining the union field correctly, it simply defined that
union's most useful field.  Define it correctly now.

Remove traits that can't be safely implemented on a union: PartialEq,
Eq, and Hash.  Define Debug, but exclude the union field.

libc-test/build.rs

@@ -2543,6 +2543,9 @@ fn test_freebsd(target: &str) {
             // not available until FreeBSD 12, and is an anonymous union there.
             ("xucred", "cr_pid__c_anonymous_union") => true,
 
+            // Anonymous union
+            ("sigevent", "_sigev_un") => true,
+
             // m_owner field is a volatile __lwpid_t
             ("umutex", "m_owner") => true,
             // c_has_waiters field is a volatile int32_t
@@ -4281,8 +4284,8 @@ fn test_linux(target: &str) {
         (musl && struct_ == "glob_t" && field == "gl_flags") ||
         // musl seems to define this as an *anonymous* bitfield
         (musl && struct_ == "statvfs" && field == "__f_unused") ||
-        // sigev_notify_thread_id is actually part of a sigev_un union
-        (struct_ == "sigevent" && field == "sigev_notify_thread_id") ||
+        // _sigev_un is an anonymous union
+        (struct_ == "sigevent" && field == "_sigev_un") ||
         // signalfd had SIGSYS fields added in Linux 4.18, but no libc release
         // has them yet.
         (struct_ == "signalfd_siginfo" && (field == "ssi_addr_lsb" ||

src/unix/bsd/freebsdlike/freebsd/mod.rs

@@ -237,20 +237,9 @@ impl ::Clone for devstat_select_mode {
 }
 
 s! {
-    pub struct aiocb {
-        pub aio_fildes: ::c_int,
-        pub aio_offset: ::off_t,
-        pub aio_buf: *mut ::c_void,
-        pub aio_nbytes: ::size_t,
-        __unused1: [::c_int; 2],
-        __unused2: *mut ::c_void,
-        pub aio_lio_opcode: ::c_int,
-        pub aio_reqprio: ::c_int,
-        // unused 3 through 5 are the __aiocb_private structure
-        __unused3: ::c_long,
-        __unused4: ::c_long,
-        __unused5: *mut ::c_void,
-        pub aio_sigevent: sigevent
+    pub struct __c_anonymous_sigev_thread {
+        pub _function: *mut ::c_void,   // Actually a function pointer
+        pub _attribute: *mut ::pthread_attr_t,
     }
 
     pub struct jail {
@@ -1345,6 +1334,32 @@ s! {
 }
 
 s_no_extra_traits! {
+    #[cfg_attr(feature = "extra_traits", derive(Debug))]
+    pub struct aiocb {
+        pub aio_fildes: ::c_int,
+        pub aio_offset: ::off_t,
+        pub aio_buf: *mut ::c_void,
+        pub aio_nbytes: ::size_t,
+        __unused1: [::c_int; 2],
+        __unused2: *mut ::c_void,
+        pub aio_lio_opcode: ::c_int,
+        pub aio_reqprio: ::c_int,
+        // unused 3 through 5 are the __aiocb_private structure
+        __unused3: ::c_long,
+        __unused4: ::c_long,
+        __unused5: *mut ::c_void,
+        pub aio_sigevent: sigevent
+    }
+
+    // Can't correctly impl Debug for unions
+    #[allow(missing_debug_implementations)]
+    pub union __c_anonymous_sigev_un {
+        pub _threadid: ::__lwpid_t,
+        pub _sigev_thread: __c_anonymous_sigev_thread,
+        pub _kevent_flags: ::c_ushort,
+        __spare__: [::c_long; 8],
+    }
+
     pub struct utmpx {
         pub ut_type: ::c_short,
         pub ut_tv: ::timeval,
@@ -1392,12 +1407,7 @@ s_no_extra_traits! {
         pub sigev_notify: ::c_int,
         pub sigev_signo: ::c_int,
         pub sigev_value: ::sigval,
-        //The rest of the structure is actually a union.  We expose only
-        //sigev_notify_thread_id because it's the most useful union member.
-        pub sigev_notify_thread_id: ::lwpid_t,
-        #[cfg(target_pointer_width = "64")]
-        __unused1: ::c_int,
-        __unused2: [::c_long; 7]
+        pub _sigev_un: __c_anonymous_sigev_un,
     }
 
     pub struct ptsstat {
@@ -1791,35 +1801,17 @@ cfg_if! {
             }
         }
 
-        impl PartialEq for sigevent {
-            fn eq(&self, other: &sigevent) -> bool {
-                self.sigev_notify == other.sigev_notify
-                    && self.sigev_signo == other.sigev_signo
-                    && self.sigev_value == other.sigev_value
-                    && self.sigev_notify_thread_id
-                        == other.sigev_notify_thread_id
-            }
-        }
-        impl Eq for sigevent {}
         impl ::fmt::Debug for sigevent {
             fn fmt(&self, f: &mut ::fmt::Formatter) -> ::fmt::Result {
                 f.debug_struct("sigevent")
                     .field("sigev_notify", &self.sigev_notify)
                     .field("sigev_signo", &self.sigev_signo)
                     .field("sigev_value", &self.sigev_value)
-                    .field("sigev_notify_thread_id",
-                           &self.sigev_notify_thread_id)
+                    // Skip _sigev_un, since we can't guarantee that it will be
+                    // properly initialized.
                     .finish()
             }
         }
-        impl ::hash::Hash for sigevent {
-            fn hash<H: ::hash::Hasher>(&self, state: &mut H) {
-                self.sigev_notify.hash(state);
-                self.sigev_signo.hash(state);
-                self.sigev_value.hash(state);
-                self.sigev_notify_thread_id.hash(state);
-            }
-        }
 
         impl PartialEq for ptsstat {
             fn eq(&self, other: &ptsstat) -> bool {

src/unix/linux_like/linux/gnu/mod.rs

@@ -49,24 +49,6 @@ s! {
         pub __statx_timestamp_pad1: [i32; 1],
     }
 
-    pub struct aiocb {
-        pub aio_fildes: ::c_int,
-        pub aio_lio_opcode: ::c_int,
-        pub aio_reqprio: ::c_int,
-        pub aio_buf: *mut ::c_void,
-        pub aio_nbytes: ::size_t,
-        pub aio_sigevent: ::sigevent,
-        __next_prio: *mut aiocb,
-        __abs_prio: ::c_int,
-        __policy: ::c_int,
-        __error_code: ::c_int,
-        __return_value: ::ssize_t,
-        pub aio_offset: off_t,
-        #[cfg(all(not(target_arch = "x86_64"), target_pointer_width = "32"))]
-        __unused1: [::c_char; 4],
-        __glibc_reserved: [::c_char; 32]
-    }
-
     pub struct __exit_status {
         pub e_termination: ::c_short,
         pub e_exit: ::c_short,
@@ -481,6 +463,27 @@ impl siginfo_t {
     }
 }
 
+s_no_extra_traits! {
+    #[cfg_attr(feature = "extra_traits", derive(Debug))]
+    pub struct aiocb {
+        pub aio_fildes: ::c_int,
+        pub aio_lio_opcode: ::c_int,
+        pub aio_reqprio: ::c_int,
+        pub aio_buf: *mut ::c_void,
+        pub aio_nbytes: ::size_t,
+        pub aio_sigevent: ::sigevent,
+        __next_prio: *mut aiocb,
+        __abs_prio: ::c_int,
+        __policy: ::c_int,
+        __error_code: ::c_int,
+        __return_value: ::ssize_t,
+        pub aio_offset: off_t,
+        #[cfg(all(not(target_arch = "x86_64"), target_pointer_width = "32"))]
+        __unused1: [::c_char; 4],
+        __glibc_reserved: [::c_char; 32]
+    }
+}
+
 // Internal, for casts to access union fields
 #[repr(C)]
 struct sifields_sigchld {

src/unix/linux_like/mod.rs

@@ -12,6 +12,11 @@ missing! {
 }
 
 s! {
+    pub struct __c_anonymous_sigev_thread {
+        pub _function: *mut ::c_void,   // Actually a function pointer
+        pub _attribute: *mut ::pthread_attr_t,
+    }
+
     pub struct in_addr {
         pub s_addr: ::in_addr_t,
     }
@@ -220,6 +225,17 @@ s_no_extra_traits! {
         pub u64: u64,
     }
 
+    // Can't correctly impl Debug for unions
+    #[allow(missing_debug_implementations)]
+    pub union __c_anonymous_sigev_un {
+        #[cfg(target_pointer_width = "64")]
+        _pad: [::c_int; (64 - 2 * 4 - 8) / 4],
+        #[cfg(target_pointer_width = "32")]
+        _pad: [::c_int; (64 - 2 * 4 - 4) / 4],
+        pub _tid: ::c_int,
+        pub _sigev_thread: __c_anonymous_sigev_thread,
+    }
+
     pub struct sockaddr_un {
         pub sun_family: sa_family_t,
         pub sun_path: [::c_char; 108]
@@ -247,13 +263,7 @@ s_no_extra_traits! {
         pub sigev_value: ::sigval,
         pub sigev_signo: ::c_int,
         pub sigev_notify: ::c_int,
-        // Actually a union.  We only expose sigev_notify_thread_id because it's
-        // the most useful member
-        pub sigev_notify_thread_id: ::c_int,
-        #[cfg(target_pointer_width = "64")]
-        __unused1: [::c_int; 11],
-        #[cfg(target_pointer_width = "32")]
-        __unused1: [::c_int; 12]
+        pub _sigev_un: __c_anonymous_sigev_un,
     }
 }
 
@@ -401,35 +411,17 @@ cfg_if! {
             }
         }
 
-        impl PartialEq for sigevent {
-            fn eq(&self, other: &sigevent) -> bool {
-                self.sigev_value == other.sigev_value
-                    && self.sigev_signo == other.sigev_signo
-                    && self.sigev_notify == other.sigev_notify
-                    && self.sigev_notify_thread_id
-                        == other.sigev_notify_thread_id
-            }
-        }
-        impl Eq for sigevent {}
         impl ::fmt::Debug for sigevent {
             fn fmt(&self, f: &mut ::fmt::Formatter) -> ::fmt::Result {
                 f.debug_struct("sigevent")
                     .field("sigev_value", &self.sigev_value)
                     .field("sigev_signo", &self.sigev_signo)
                     .field("sigev_notify", &self.sigev_notify)
-                    .field("sigev_notify_thread_id",
-                           &self.sigev_notify_thread_id)
+                    // Skip _sigev_un, since we can't guarantee that it will be
+                    // properly initialized.
                     .finish()
             }
         }
-        impl ::hash::Hash for sigevent {
-            fn hash<H: ::hash::Hasher>(&self, state: &mut H) {
-                self.sigev_value.hash(state);
-                self.sigev_signo.hash(state);
-                self.sigev_notify.hash(state);
-                self.sigev_notify_thread_id.hash(state);
-            }
-        }
     }
 }