Make compare-strings more compatible with old behavior.

* fns.c (Fcompare_strings): Silently bring too-large ends into range.

Fixes: debbugs:17903

2 files changed, 15 insertions, 3 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 8ffc1c56675..0125f4c93e2 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,8 @@
+2014-08-02  Paul Eggert  <eggert@cs.ucla.edu>
+
+        Make compare-strings more compatible with old behavior (Bug#17903).
+        * fns.c (Fcompare_strings): Silently bring too-large ends into range.
+
 2014-08-02  Jan Djärv  <jan.h.d@swipnet.se>
 
         * gtkutil.c (create_dialog): Force min spacing 10 between buttons.
diff --git a/src/fns.c b/src/fns.c
index 79967116a11..33c02598359 100644
--- a/src/fns.c
+++ b/src/fns.c
@@ -253,6 +253,13 @@ If string STR1 is greater, the value is a positive number N;
   CHECK_STRING (str1);
   CHECK_STRING (str2);
 
+  /* For backward compatibility, silently bring too-large positive end
+     values into range.  */
+  if (INTEGERP (end1) && SCHARS (str1) < XINT (end1))
+    end1 = make_number (SCHARS (str1));
+  if (INTEGERP (end2) && SCHARS (str2) < XINT (end2))
+    end2 = make_number (SCHARS (str2));
+
   validate_subarray (str1, start1, end1, SCHARS (str1), &from1, &to1);
   validate_subarray (str2, start2, end2, SCHARS (str2), &from2, &to2);
 
@@ -1720,7 +1727,7 @@ See also the function `nreverse', which is used more often.  */)
   else if (VECTORP (seq))
     {
       ptrdiff_t i, size = ASIZE (seq);
-      
+
       new = make_uninit_vector (size);
       for (i = 0; i < size; i++)
         ASET (new, i, AREF (seq, size - i - 1));
@@ -1737,7 +1744,7 @@ See also the function `nreverse', which is used more often.  */)
   else if (STRINGP (seq))
     {
       ptrdiff_t size = SCHARS (seq), bytes = SBYTES (seq);
-      
+
       if (size == bytes)
         {
           ptrdiff_t i;
@@ -1755,7 +1762,7 @@ See also the function `nreverse', which is used more often.  */)
           while (q > SDATA (new))
             {
               int ch, len;
-              
+
               ch = STRING_CHAR_AND_LENGTH (p, len);
               p += len, q -= len;
               CHAR_STRING (ch, q);