ash: fix "ash -c 'exec 1>&0'" complaining that fd 0 is busy

1 files changed, 10 insertions, 4 deletions

diff --git a/shell/ash.c b/shell/ash.c
index b33351674..179d9257b 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -11684,7 +11684,8 @@ expandstr(const char *ps)
 {
         union node n;
 
-        /* XXX Fix (char *) cast. */
+        /* XXX Fix (char *) cast. It _is_ a bug. ps is variable's value,
+         * and token processing _can_ alter it (delete NULs etc). */
         setinputstring((char *)ps);
         readtoken1(pgetc(), PSSYNTAX, nullstr, 0);
         popfile();
@@ -13802,15 +13803,20 @@ int ash_main(int argc UNUSED_PARAM, char **argv)
         }
  state3:
         state = 4;
-        if (minusc)
+        if (minusc) {
+                /* evalstring pushes parsefile stack.
+                 * Ensure we don't falsely claim that 0 (stdin)
+                 * is one of stacked source fds */
+                if (!sflag)
+                        g_parsefile->fd = -1;
                 evalstring(minusc, 0);
+        }
 
         if (sflag || minusc == NULL) {
 #if ENABLE_FEATURE_EDITING_SAVEHISTORY
                 if (iflag) {
                         const char *hp = lookupvar("HISTFILE");
-
-                        if (hp != NULL)
+                        if (hp)
                                 line_input_state->hist_file = hp;
                 }
 #endif