emacs-27 d03f2a6: Avoid assertion violation in callproc.c

[Eli Zaretskii]

branch: emacs-27
commit d03f2a6ee942882c5bc78226b4730dac6f1d0916
Author: Eli Zaretskii <eliz@gnu.org>
Commit: Eli Zaretskii <eliz@gnu.org>

    Avoid assertion violation in callproc.c
    
    * src/callproc.c (call_process): Avoid assertion violation when
    DESTINATION is a cons cell '(:file . "FOO")'.  (Bug#46426)
---
 src/callproc.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/callproc.c b/src/callproc.c
index 5b1d8bf..3eac38d 100644
--- a/src/callproc.c
+++ b/src/callproc.c
@@ -394,7 +394,11 @@ call_process (ptrdiff_t nargs, Lisp_Object *args, int 
filefd,
       /* If the buffer is (still) a list, it might be a (:file "file") spec. */
       if (CONSP (buffer) && EQ (XCAR (buffer), QCfile))
        {
-         output_file = Fexpand_file_name (XCAR (XCDR (buffer)),
+         Lisp_Object ofile = XCDR (buffer);
+         if (CONSP (ofile))
+           ofile = XCAR (ofile);
+         CHECK_STRING (ofile);
+         output_file = Fexpand_file_name (ofile,
                                           BVAR (current_buffer, directory));
          CHECK_STRING (output_file);
          buffer = Qnil;