2 files changed, 8 insertions, 1 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 5ced4734bc9..d46e34c8525 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,9 @@
+2015-01-21  Paul Eggert  <eggert@cs.ucla.edu>
+
+        Fix coding.c subscript error
+        * coding.c (CODING_ISO_INVOKED_CHARSET):
+        Avoid undefined behavior if CODING_ISO_INVOCATION returns negative.
+
 2015-01-17  Eli Zaretskii  <eliz@gnu.org>
 
         * xdisp.c (produce_image_glyph): Fix display of images in R2L
diff --git a/src/coding.c b/src/coding.c
index 54811588c6a..a7128ee3e73 100644
--- a/src/coding.c
+++ b/src/coding.c
@@ -350,7 +350,8 @@ static Lisp_Object Vbig5_coding_system;
 #define CODING_ISO_BOL(coding)  \
   ((coding)->spec.iso_2022.bol)
 #define CODING_ISO_INVOKED_CHARSET(coding, plane)       \
-  CODING_ISO_DESIGNATION ((coding), CODING_ISO_INVOCATION ((coding), (plane)))
+  (CODING_ISO_INVOCATION (coding, plane) < 0 ? -1       \
+   : CODING_ISO_DESIGNATION (coding, CODING_ISO_INVOCATION (coding, plane)))
 #define CODING_ISO_CMP_STATUS(coding)   \
   (&(coding)->spec.iso_2022.cmp_status)
 #define CODING_ISO_EXTSEGMENT_LEN(coding)       \