fix: prevent child processes from inheriting ui channel file descriptors

1 files changed, 6 insertions, 2 deletions

diff --git a/src/nvim/channel.c b/src/nvim/channel.c
index 0222a134a7..b64edae2bf 100644
--- a/src/nvim/channel.c
+++ b/src/nvim/channel.c
@@ -544,8 +544,12 @@ uint64_t channel_from_stdio(bool rpc, CallbackReader on_output, const char **err
   }
 #else
   if (embedded_mode) {
-    stdin_dup_fd = dup(STDIN_FILENO);
-    stdout_dup_fd = dup(STDOUT_FILENO);
+    // In embedded mode redirect stdout and stdin to stderr, since they are used for the UI channel.
+    // NOTE: fnctl with F_DUPFD_CLOEXEC is used instead of dup to prevent child processes from
+    // inheriting the file descriptors, which make it impossible for UIs to detect when nvim exits
+    // while one or more of its child processes are still running.
+    stdin_dup_fd = fcntl(STDIN_FILENO, F_DUPFD_CLOEXEC, STDERR_FILENO + 1);
+    stdout_dup_fd = fcntl(STDOUT_FILENO, F_DUPFD_CLOEXEC, STDERR_FILENO + 1);
     dup2(STDERR_FILENO, STDOUT_FILENO);
     dup2(STDERR_FILENO, STDIN_FILENO);
   }