mame	2018-11-07 07:55:57 +0900 (Wed, 07 Nov 2018)

  New Revision: 65584

  https://svn.ruby-lang.org/cgi-bin/viewvc.cgi?view=revision&revision=65584

  Log:
    Revert "thread.c (rb_wait_for_single_fd): no point initializing pollfd.revents"
    
    It may cause an access to uninitialized variables.
    The call to ppoll will set the `revents` field, but ppoll is not always
    called because it is in the guard `!RUBY_VM_INTERRUPTED(th->ec)`.
    This issue was found by Coverity Scan.

  Modified files:
    trunk/thread.c
Index: thread.c
===================================================================
--- thread.c	(revision 65583)
+++ thread.c	(revision 65584)
@@ -4043,10 +4043,12 @@ rb_wait_for_single_fd(int fd, int events https://github.com/ruby/ruby/blob/trunk/thread.c#L4043
     fds[0].fd = fd;
     fds[0].events = (short)events;
     do {
+        fds[0].revents = 0;
         fds[1].fd = rb_sigwait_fd_get(th);
 
         if (fds[1].fd >= 0) {
             fds[1].events = POLLIN;
+            fds[1].revents = 0;
             nfds = 2;
             ubf = ubf_sigwait;
         }
@@ -4070,6 +4072,7 @@ rb_wait_for_single_fd(int fd, int events https://github.com/ruby/ruby/blob/trunk/thread.c#L4072
         if (fds[1].fd >= 0) {
             if (result > 0 && fds[1].revents) {
                 result--;
+                fds[1].revents = 0;
             }
             (void)check_signals_nogvl(th, fds[1].fd);
             rb_sigwait_fd_put(th, fds[1].fd);

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