Fix I2892: Implement sys/select pselect method (#2895)

posixlib/src/main/resources/scala-native/sys/select.c

@@ -65,6 +65,8 @@ int scalanative_fd_isset(int fd, struct scalanative_fd_set *set) {
     return FD_ISSET(fd, (fd_set *)set);
 }
 
+//  pselect() is straight call through, so no declaration here.
+
 int scalanative_select(int nfds, struct scalanative_fd_set *readfds,
                        struct scalanative_fd_set *writefds,
                        struct scalanative_fd_set *exceptfds,

posixlib/src/main/scala/scala/scalanative/posix/sys/select.scala

@@ -1,17 +1,32 @@
-package scala.scalanative.posix.sys
+package scala.scalanative
+package posix
+package sys
 
 import scalanative.unsafe._
 import scalanative.unsafe.Nat._
 
+/** POSIX select.h for Scala
+ *
+ *  @see
+ *    The Open Group Base Specifications
+ *    [[https://pubs.opengroup.org/onlinepubs/9699919799 Issue 7, 2018]]
+ *    edition.
+ */
 @extern
 object select {
 
-  // posix requires this file declares suseconds_t. Use single point of truth.
+  // Use single points of truth for types required by POSIX specification.
 
+  type time_t = types.time_t
   type suseconds_t = types.suseconds_t
 
+  type sigset_t = posix.signal.sigset_t
+
+  type timespec = posix.time.timespec
+  type timeval = sys.time.timeval
+
   // The declaration of type fd_set closely follows the Linux C declaration.
-  // glibc circa March 2019 and many years prior is documented as using a
+  // glibc, circa March 2019 and many years prior, is documented as using a
   // fixed buffer of 1024 bits.
   //
   // Since "extern object may only contain extern fields and methods"
@@ -28,26 +43,43 @@ object select {
 
   type fd_set = CStruct1[CArray[CLongInt, _16]]
 
-  // Allocation & usage example:
-  //
-  // An fd_set is arguably too large to allocate on the stack, so use a Zone.
-  //
-  //    import scalanative.unsafe.{Zone, alloc}
-  //
-  //    Zone {
-  //
-  //        // Zone.alloc is documented as returning zeroed memory.
-  //        val fdsetPtr = alloc[fd_set] //  No need to FD_ZERO.
-  //        FD_SET(sock, fdsetPtr)
-  //
-  //        // If used, allocate writefds and/or exceptfds the same way.
-  //
-  //        val result = select(nfds, fdsetPtr, writefds, exceptfds)
-  //        // check result.
-  //        // do work implied by result.
-  //
-  //    } // fdsetPtr and memory it points to are not valid outsize of Zone.
+  /* Allocation & usage example:
+   *
+   * An fd_set is arguably too large to allocate on the stack, so use a Zone.
+   *
+   *	import scalanative.unsafe.{Zone, alloc}
+   *
+   *	Zone {
+   *	    // Zone.alloc is documented as returning zeroed memory.
+   *	    val fdsetPtr = alloc[fd_set] //  No need to FD_ZERO.
+   * 	    FD_SET(sock, fdsetPtr)
+   *
+   * 	    // If used, allocate writefds and/or exceptfds the same way.
+   *
+   * 	    val result = select(nfds, fdsetPtr, writefds, exceptfds, timeout)
+   * 	    // check result.
+   * 	    // do work implied by result.
+   *
+   * 	} // fdsetPtr and memory it points to are not valid outsize of Zone.
+   */
+
+  /* Declare pselect() as a direct call through to C. There no
+   * @name("scalanative_pselect") is needed.
+   * Guard code exists to ensure match with operating system at compile time.
+   *   fd_set is guarded by code in select.c
+   *   timespec is guarded by code in time.c (distinct from sys/time.c)
+   */
+
+  def pselect(
+      nfds: CInt,
+      readfds: Ptr[fd_set],
+      writefds: Ptr[fd_set],
+      exceptfds: Ptr[fd_set],
+      timeout: Ptr[timespec],
+      sigmask: sigset_t
+  ): CInt = extern
 
+  // select() is a excellent candidate to be changed to use direct call-thru.
   @name("scalanative_select")
   def select(
       nfds: CInt,