Ensure that expand-file-name returns an absolute file name

* src/fileio.c (Fexpand_file_name): Don't directly use the current
buffer's default-directory if it is relative.  Instead replace it
by its expansion relative to invocation-directory.  (Bug#36502)
* test/src/fileio-tests.el
(fileio-tests--relative-default-directory): New test.

1 files changed, 5 insertions, 0 deletions

diff --git a/test/src/fileio-tests.el b/test/src/fileio-tests.el
index bd827e5498f..8788c830c94 100644
--- a/test/src/fileio-tests.el
+++ b/test/src/fileio-tests.el
@@ -126,3 +126,8 @@ Also check that an encoding error can appear in a symlink."
               (should (equal c1 (char-before)))
               (should (equal c1 (char-after))))))
       (if f (delete-file f)))))
+
+(ert-deftest fileio-tests--relative-default-directory ()
+  "Test expand-file-name when default-directory is relative."
+  (let ((default-directory "some/relative/name"))
+    (should (file-name-absolute-p (expand-file-name "foo")))))