Fix wrong logic for moving filedescriptors leading to closed stdin

With this fix, tests can now use /dev/null as stdin.

Fixes #2165

1 files changed, 6 insertions, 1 deletions

diff --git a/src/shell_manager.cc b/src/shell_manager.cc
index 3615567e..6aa2b31d 100644
--- a/src/shell_manager.cc
+++ b/src/shell_manager.cc
@@ -167,7 +167,12 @@ std::pair<String, int> ShellManager::eval(
     Pipe child_stdin{not input.empty()}, child_stdout, child_stderr;
     pid_t pid = spawn_shell(m_shell.c_str(), cmdline, shell_context.params, kak_env,
                             [&child_stdin, &child_stdout, &child_stderr] {
-        auto move = [](int oldfd, int newfd) { dup2(oldfd, newfd); close(oldfd); };
+        auto move = [](int oldfd, int newfd)
+        {
+            if (oldfd == newfd)
+                return;
+            dup2(oldfd, newfd); close(oldfd);
+        };
 
         if (child_stdin.read_fd() != -1)
         {