Fix valgrind report in call-interactively

* src/callint.c (Fcall_interactively): Don't try to access more
bytes than are available in the interactive spec.  (Bug#30004)

1 files changed, 17 insertions, 4 deletions

diff --git a/src/callint.c b/src/callint.c
index ef228517f17..e4491e9085a 100644
--- a/src/callint.c
+++ b/src/callint.c
@@ -774,10 +774,23 @@ invoke it.  If KEYS is omitted or nil, the return value of
              if anyone tries to define one here.  */
         case '+':
         default:
-          error ("Invalid control letter `%c' (#o%03o, #x%04x) in interactive calling string",
-                 STRING_CHAR ((unsigned char *) tem),
-                 (unsigned) STRING_CHAR ((unsigned char *) tem),
-                 (unsigned) STRING_CHAR ((unsigned char *) tem));
+          {
+            /* How many bytes are left unprocessed in the specs string?
+               (Note that this excludes the trailing null byte.)  */
+            ptrdiff_t bytes_left = SBYTES (specs) - (tem - string);
+            unsigned letter;
+
+            /* If we have enough bytes left to treat the sequence as a
+               character, show that character's codepoint; otherwise
+               show only its first byte.  */
+            if (bytes_left >= BYTES_BY_CHAR_HEAD (*((unsigned char *) tem)))
+              letter = STRING_CHAR ((unsigned char *) tem);
+            else
+              letter = *((unsigned char *) tem);
+
+            error ("Invalid control letter `%c' (#o%03o, #x%04x) in interactive calling string",
+                   (int) letter, letter, letter);
+          }
         }
 
       if (varies[i] == 0)