diff --git a/lib-src/ChangeLog b/lib-src/ChangeLog
index a5d20af4263..cb847669deb 100644
--- a/lib-src/ChangeLog
+++ b/lib-src/ChangeLog
@@ -1,5 +1,11 @@
 2011-03-21  Paul Eggert  <eggert@cs.ucla.edu>
 
+	etags: In Prolog functions, don't assume int fits in size_t.
+	This avoids a warning with gcc -Wstrict-overflow.
+	* etags.c (Prolog_functions, prolog_pr, prolog_atom): Use size_t,
+	not int, to store sizes.
+	(prolog_atom): Return 0, not -1, on error.  All callers changed.
+
 	update-game-score: fix bug with -r
 	* update-game-score.c (main): Don't set 'scores' to garbage when
 	-r is specified and scorecount != MAX_SCORES (Bug#8310).  This bug
diff --git a/lib-src/etags.c b/lib-src/etags.c
index 385e4cc9721..0c14a0d1663 100644
--- a/lib-src/etags.c
+++ b/lib-src/etags.c
@@ -5254,16 +5254,16 @@ HTML_labels (FILE *inf)
  * Original code by Sunichirou Sugou (1989)
  * Rewritten by Anders Lindgren (1996)
  */
-static int prolog_pr (char *, char *);
+static size_t prolog_pr (char *, char *);
 static void prolog_skip_comment (linebuffer *, FILE *);
-static int prolog_atom (char *, int);
+static size_t prolog_atom (char *, size_t);
 
 static void
 Prolog_functions (FILE *inf)
 {
   char *cp, *last;
-  int len;
-  int allocated;
+  size_t len;
+  size_t allocated;
 
   allocated = 0;
   len = 0;
@@ -5320,16 +5320,16 @@ prolog_skip_comment (linebuffer *plb, FILE *inf)
  * Return the size of the name of the predicate or rule, or 0 if no
  * header was found.
  */
-static int
+static size_t
 prolog_pr (char *s, char *last)
 
                 		/* Name of last clause. */
 {
-  int pos;
-  int len;
+  size_t pos;
+  size_t len;
 
   pos = prolog_atom (s, 0);
-  if (pos < 1)
+  if (! pos)
     return 0;
 
   len = pos;
@@ -5339,7 +5339,7 @@ prolog_pr (char *s, char *last)
        || (s[pos] == '(' && (pos += 1))
        || (s[pos] == ':' && s[pos + 1] == '-' && (pos += 2)))
       && (last == NULL		/* save only the first clause */
-	  || len != (int)strlen (last)
+	  || len != strlen (last)
 	  || !strneq (s, last, len)))
 	{
 	  make_tag (s, len, TRUE, s, pos, lineno, linecharno);
@@ -5351,17 +5351,17 @@ prolog_pr (char *s, char *last)
 
 /*
  * Consume a Prolog atom.
- * Return the number of bytes consumed, or -1 if there was an error.
+ * Return the number of bytes consumed, or 0 if there was an error.
  *
  * A prolog atom, in this context, could be one of:
  * - An alphanumeric sequence, starting with a lower case letter.
  * - A quoted arbitrary string. Single quotes can escape themselves.
  *   Backslash quotes everything.
  */
-static int
-prolog_atom (char *s, int pos)
+static size_t
+prolog_atom (char *s, size_t pos)
 {
-  int origpos;
+  size_t origpos;
 
   origpos = pos;
 
@@ -5390,11 +5390,11 @@ prolog_atom (char *s, int pos)
 	    }
 	  else if (s[pos] == '\0')
 	    /* Multiline quoted atoms are ignored. */
-	    return -1;
+	    return 0;
 	  else if (s[pos] == '\\')
 	    {
 	      if (s[pos+1] == '\0')
-		return -1;
+		return 0;
 	      pos += 2;
 	    }
 	  else
@@ -5403,7 +5403,7 @@ prolog_atom (char *s, int pos)
       return pos - origpos;
     }
   else
-    return -1;
+    return 0;
 }