Make call-process work if exec-path is nil

* src/lread.c (openp): If exec-path is nil, no files would be
found to execute (bug#30564).

Test cases:

 (let ((exec-path ()))
   (call-process "/bin/ls" nil (current-buffer)))

This would previously fail, but now works.

 (let ((exec-path '("/bin/")))
   (call-process "ls" nil (current-buffer)))

This worked, and still works.

1 files changed, 7 insertions, 3 deletions

diff --git a/src/lread.c b/src/lread.c
index 8fb61f56338..8019443c09f 100644
--- a/src/lread.c
+++ b/src/lread.c
@@ -1587,11 +1587,14 @@ openp (Lisp_Object path, Lisp_Object str, Lisp_Object suffixes,
 
   absolute = complete_filename_p (str);
 
-  for (; CONSP (path); path = XCDR (path))
+  do
     {
       ptrdiff_t baselen, prefixlen;
 
-      filename = Fexpand_file_name (str, XCAR (path));
+      if (NILP (path))
+        filename = str;
+      else
+        filename = Fexpand_file_name (str, XCAR (path));
       if (!complete_filename_p (filename))
         /* If there are non-absolute elts in PATH (eg ".").  */
         /* Of course, this could conceivably lose if luser sets
@@ -1768,7 +1771,8 @@ openp (Lisp_Object path, Lisp_Object str, Lisp_Object suffixes,
         }
       if (absolute)
         break;
-    }
+      path = XCDR (path);
+    } while (CONSP (path));
 
   SAFE_FREE ();
   errno = last_errno;