input: stream_set_blocking(): libuv impl

- Create a private libuv loop instead of re-using uv_default_loop(), to
  avoid conflict[1] with existing watcher(s) on the fd.
- Expose the global "input" fd as a getter instead of a mutable global.

[1] .deps/build/src/libuv/src/unix/core.c:833:
      uv__io_stop: Assertion `loop->watchers[w->fd] == w' failed.

3 files changed, 20 insertions, 18 deletions

diff --git a/src/nvim/os/input.c b/src/nvim/os/input.c
index 5dcaee8304..f89ca4af95 100644
--- a/src/nvim/os/input.c
+++ b/src/nvim/os/input.c
@@ -35,6 +35,7 @@ typedef enum {
 static RStream *read_stream = NULL;
 static RBuffer *read_buffer = NULL, *input_buffer = NULL;
 static bool input_eof = false;
+static int global_fd = 0;
 
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "os/input.c.generated.h"
@@ -47,12 +48,19 @@ void input_init(void)
   input_buffer = rbuffer_new(INPUT_BUFFER_SIZE + MAX_KEY_CODE_LEN);
 }
 
+/// Gets the file from which input was gathered at startup.
+int input_global_fd(void)
+{
+  return global_fd;
+}
+
 void input_start_stdin(int fd)
 {
   if (read_stream) {
     return;
   }
 
+  global_fd = fd;
   read_buffer = rbuffer_new(READ_BUFFER_SIZE);
   read_stream = rstream_new(read_cb, read_buffer, NULL);
   rstream_set_file(read_stream, fd);
@@ -62,14 +70,9 @@ void input_start_stdin(int fd)
 void input_stop_stdin(void)
 {
   if (!read_stream) {
-    // In some cases (i.e. "nvim && read") where we do not explicitly play with
-    // std{in,out,err}, some other module/library nevertheless sets the stream
-    // to non-blocking; we still must "fix" the stream (#2598) in those cases.
-    stream_set_blocking(global_input_fd, true);  // normalize stream (#2598)
     return;
   }
 
-  rstream_set_blocking(read_stream, true);  // normalize stream (#2598)
   rstream_stop(read_stream);
   rstream_free(read_stream);
   read_stream = NULL;
diff --git a/src/nvim/os/rstream.c b/src/nvim/os/rstream.c
index 55bf89d768..702f282d53 100644
--- a/src/nvim/os/rstream.c
+++ b/src/nvim/os/rstream.c
@@ -297,11 +297,6 @@ void rstream_stop(RStream *rstream)
   }
 }
 
-int rstream_set_blocking(RStream *rstream, bool blocking)
-{
-  return uv_stream_set_blocking(rstream->stream, blocking);
-}
-
 /// Returns the number of bytes ready for consumption in `rstream`
 size_t rstream_pending(RStream *rstream)
 {
diff --git a/src/nvim/os/stream.c b/src/nvim/os/stream.c
index 35cb41081d..0c448872c3 100644
--- a/src/nvim/os/stream.c
+++ b/src/nvim/os/stream.c
@@ -14,13 +14,17 @@
 /// @return `0` on success, or `-errno` on failure.
 int stream_set_blocking(int fd, bool blocking)
 {
-  int flags = fcntl(fd, F_GETFL, 0);
-  int err = 0;
-  if (!blocking && !(flags & O_NONBLOCK)) {
-    err = fcntl(fd, F_SETFL, flags | O_NONBLOCK);
-  } else if (blocking && (flags & O_NONBLOCK)) {
-    err = fcntl(fd, F_SETFL, flags & ~O_NONBLOCK);
-  }
-  return err == -1 ? -errno : 0;
+  // Private loop to avoid conflict with existing watcher(s):
+  //    uv__io_stop: Assertion `loop->watchers[w->fd] == w' failed.
+  uv_loop_t loop;
+  uv_pipe_t stream;
+  uv_loop_init(&loop);
+  uv_pipe_init(&loop, &stream, 0);
+  uv_pipe_open(&stream, fd);
+  int retval = uv_stream_set_blocking((uv_stream_t *)&stream, blocking);
+  uv_close((uv_handle_t *)&stream, NULL);
+  uv_run(&loop, UV_RUN_NOWAIT);  // not necessary, but couldn't hurt.
+  uv_loop_close(&loop);
+  return retval;
 }