2 files changed, 17 insertions, 0 deletions

diff --git a/src/.gdbinit b/src/.gdbinit
index 67dcf718e3c..3cebdff5e7b 100644
--- a/src/.gdbinit
+++ b/src/.gdbinit
@@ -119,6 +119,12 @@ Print the value of the lisp variable given as argument.
 Works only when an inferior emacs is executing.
 end
 
+# Format the value and print it as a string. Works in
+# an rr session and during live debugging. Calls into lisp.
+define xfmt
+  printf "%s\n", debug_format("%S", $arg0)
+end
+
 # Print out current buffer point and boundaries
 define ppt
   set $b = current_buffer
diff --git a/src/print.c b/src/print.c
index 83943752204..234f44a4a5d 100644
--- a/src/print.c
+++ b/src/print.c
@@ -855,6 +855,17 @@ safe_debug_print (Lisp_Object arg)
     }
 }
 
+/* This function formats the given object and returns the result as a
+   string. Use this in contexts where you can inspect strings, but
+   where stderr output won't work --- e.g., while replaying rr
+   recordings.  */
+const char * debug_format (const char *, Lisp_Object) EXTERNALLY_VISIBLE;
+const char *
+debug_format (const char *fmt, Lisp_Object arg)
+{
+  return SSDATA (CALLN (Fformat, build_string (fmt), arg));
+}
+
 
 DEFUN ("error-message-string", Ferror_message_string, Serror_message_string,
        1, 1, 0,