From 6f868fe1ded4d4137412cc1aae61373e9b0c941a Mon Sep 17 00:00:00 2001
From: Justine Tunney <jtunney@gmail.com>
Date: Wed, 11 Sep 2024 17:13:23 -0700
Subject: [PATCH] Fix polling of files on Windows

---
 libc/calls/poll-nt.c        |  4 +++-
 test/libc/calls/poll_test.c | 33 +++++++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/libc/calls/poll-nt.c b/libc/calls/poll-nt.c
index 6b9c1d233..867cfd108 100644
--- a/libc/calls/poll-nt.c
+++ b/libc/calls/poll-nt.c
@@ -179,7 +179,7 @@ textwindows static int sys_poll_nt_impl(struct pollfd *fds, uint64_t nfds,
 
     // check input status of pipes / consoles without blocking
     // this ensures any socket fds won't starve them of events
-    // if a file handle is POLLOUT only, we just mark it ready
+    // we can't poll file handles, so we just mark those ready
     for (i = 0; i < pn; ++i) {
       fi = fileindices[i];
       ev = fds[fi].events;
@@ -215,6 +215,8 @@ textwindows static int sys_poll_nt_impl(struct pollfd *fds, uint64_t nfds,
             fds[fi].revents = fds[fi].events & (POLLRDNORM_ | POLLWRNORM_);
             break;
         }
+      } else {
+        fds[fi].revents = fds[fi].events & (POLLRDNORM_ | POLLWRNORM_);
       }
       rc += !!fds[fi].revents;
     }
diff --git a/test/libc/calls/poll_test.c b/test/libc/calls/poll_test.c
index 97f429b27..12cf78951 100644
--- a/test/libc/calls/poll_test.c
+++ b/test/libc/calls/poll_test.c
@@ -310,6 +310,39 @@ TEST(poll, pipein_pollout_blocks) {
   EXPECT_SYS(0, 0, close(pipefds[0]));
 }
 
+TEST(poll, pipein_file_noblock) {
+  if (IsFreebsd() || IsOpenbsd())
+    return;
+  int pipefds[2];
+  EXPECT_SYS(0, 3, open("boop", O_CREAT | O_RDWR | O_TRUNC, 0644));
+  EXPECT_SYS(0, 0, pipe(pipefds));
+  struct pollfd fds[] = {{pipefds[0], POLLIN}, {3, POLLIN}};
+  EXPECT_SYS(0, 1, poll(fds, 2, -1u));
+  EXPECT_TRUE(!!(fds[1].revents & POLLIN));
+  EXPECT_TRUE(!(fds[1].revents & POLLOUT));
+  EXPECT_SYS(0, 0, close(pipefds[1]));
+  EXPECT_SYS(0, 0, close(pipefds[0]));
+  EXPECT_SYS(0, 0, close(3));
+}
+
+TEST(poll, pipein_file_noblock2) {
+  if (IsFreebsd() || IsOpenbsd())
+    return;
+  int pipefds[2];
+  EXPECT_SYS(0, 3, open("boop", O_CREAT | O_RDWR | O_TRUNC, 0644));
+  EXPECT_SYS(0, 0, pipe(pipefds));
+  EXPECT_SYS(0, 1, write(5, "x", 1));
+  struct pollfd fds[] = {{pipefds[0], POLLIN}, {3, POLLIN | POLLOUT}};
+  EXPECT_SYS(0, 2, poll(fds, 2, -1u));
+  EXPECT_TRUE(!!(fds[0].revents & POLLIN));
+  EXPECT_TRUE(!(fds[0].revents & POLLOUT));
+  EXPECT_TRUE(!!(fds[1].revents & POLLIN));
+  EXPECT_TRUE(!!(fds[1].revents & POLLOUT));
+  EXPECT_SYS(0, 0, close(pipefds[1]));
+  EXPECT_SYS(0, 0, close(pipefds[0]));
+  EXPECT_SYS(0, 0, close(3));
+}
+
 TEST(poll, pipeout_pollout) {
   int pipefds[2];
   EXPECT_SYS(0, 0, pipe(pipefds));