main: Temporary fix assertion error

This variant uses `fdopen()` which is not standard, but it fixes problem on my 
system. In next commit `scriptin` will use `FileDescriptor*` from os/fileio in 
place of `FILE*`.

2 files changed, 26 insertions, 1 deletions

diff --git a/src/nvim/main.c b/src/nvim/main.c
index 99dd9fc18f..ce0426bd8e 100644
--- a/src/nvim/main.c
+++ b/src/nvim/main.c
@@ -1057,7 +1057,9 @@ scripterror:
               mch_exit(2);
             }
             if (STRCMP(argv[0], "-") == 0) {
-              scriptin[0] = stdin;
+              const int stdin_dup_fd = os_dup(STDIN_FILENO);
+              FILE *const stdin_dup = fdopen(stdin_dup_fd, "r");
+              scriptin[0] = stdin_dup;
             } else if ((scriptin[0] = mch_fopen(argv[0], READBIN)) == NULL) {
               mch_errmsg(_("Cannot open for reading: \""));
               mch_errmsg(argv[0]);
diff --git a/src/nvim/os/fs.c b/src/nvim/os/fs.c
index 2beeae7ec6..9ce50d4afd 100644
--- a/src/nvim/os/fs.c
+++ b/src/nvim/os/fs.c
@@ -430,6 +430,29 @@ int os_close(const int fd)
   return r;
 }
 
+/// Duplicate file descriptor
+///
+/// @param[in]  fd  File descriptor to duplicate.
+///
+/// @return New file descriptor or libuv error code (< 0).
+int os_dup(const int fd)
+  FUNC_ATTR_WARN_UNUSED_RESULT
+{
+  int ret;
+os_dup_dup:
+  ret = dup(fd);
+  if (ret < 0) {
+    const int error = os_translate_sys_error(errno);
+    errno = 0;
+    if (error == UV_EINTR) {
+      goto os_dup_dup;
+    } else {
+      return error;
+    }
+  }
+  return ret;
+}
+
 /// Read from a file
 ///
 /// Handles EINTR and ENOMEM, but not other errors.