hush: strip NULs from file input, they are PITA/impossible to handle correctly

function                                             old     new   delta
file_peek                                             89      93      +4
file_get                                             260     264      +4

1 files changed, 8 insertions, 6 deletions

diff --git a/shell/hush.c b/shell/hush.c
index dbb38719a..fa85ad533 100644
--- a/shell/hush.c
+++ b/shell/hush.c
@@ -1225,6 +1225,7 @@ static int file_get(struct in_str *i)
                 ch = *i->p++;
                 if (i->eof_flag && !*i->p)
                         ch = EOF;
+                /* note: ch is never NUL */
         } else {
                 /* need to double check i->file because we might be doing something
                  * more complicated by now, like sourcing or substituting. */
@@ -1238,9 +1239,9 @@ static int file_get(struct in_str *i)
                         goto take_cached;
                 }
 #endif
-                ch = fgetc(i->file);
+                do ch = fgetc(i->file); while (ch == '\0');
         }
-        debug_printf("file_get: got a '%c' %d\n", ch, ch);
+        debug_printf("file_get: got '%c' %d\n", ch, ch);
 #if ENABLE_HUSH_INTERACTIVE
         if (ch == '\n')
                 i->promptme = 1;
@@ -1248,8 +1249,8 @@ static int file_get(struct in_str *i)
         return ch;
 }
 
-/* All the callers guarantee this routine will never be
- * used right after a newline, so prompting is not needed.
+/* All callers guarantee this routine will never
+ * be used right after a newline, so prompting is not needed.
  */
 static int file_peek(struct in_str *i)
 {
@@ -1258,13 +1259,14 @@ static int file_peek(struct in_str *i)
                 if (i->eof_flag && !i->p[1])
                         return EOF;
                 return *i->p;
+                /* note: ch is never NUL */
         }
-        ch = fgetc(i->file);
+        do ch = fgetc(i->file); while (ch == '\0');
         i->eof_flag = (ch == EOF);
         i->peek_buf[0] = ch;
         i->peek_buf[1] = '\0';
         i->p = i->peek_buf;
-        debug_printf("file_peek: got a '%c' %d\n", *i->p, *i->p);
+        debug_printf("file_peek: got '%c' %d\n", ch, ch);
         return ch;
 }