nobu	2015-07-29 16:00:25 +0900 (Wed, 29 Jul 2015)

  New Revision: 51428

  http://svn.ruby-lang.org/cgi-bin/viewvc.cgi?view=revision&revision=51428

  Log:
    string.c: empty non-embed case
    
    * string.c (str_buf_cat): consider empty non-embed string case,
      not to loop infinitely.  [ruby-core:70074] [Bug #11383]

  Modified files:
    trunk/ChangeLog
    trunk/string.c
Index: ChangeLog
===================================================================
--- ChangeLog	(revision 51427)
+++ ChangeLog	(revision 51428)
@@ -1,3 +1,8 @@ https://github.com/ruby/ruby/blob/trunk/ChangeLog#L1
+Wed Jul 29 16:00:22 2015  Nobuyoshi Nakada  <nobu@r...>
+
+	* string.c (str_buf_cat): consider empty non-embed string case,
+	  not to loop infinitely.  [ruby-core:70074] [Bug #11383]
+
 Wed Jul 29 15:25:19 2015  Nobuyoshi Nakada  <nobu@r...>
 
 	* vm_eval.c (send_internal): set method_missing_reason before
Index: string.c
===================================================================
--- string.c	(revision 51427)
+++ string.c	(revision 51428)
@@ -2292,12 +2292,17 @@ str_buf_cat(VALUE str, const char *ptr, https://github.com/ruby/ruby/blob/trunk/string.c#L2292
     }
     total = olen + len;
     if (capa <= total) {
-	while (total > capa) {
-	    if (capa > LONG_MAX / 2) {
-		capa = (total + 4095) / 4096 * 4096;
-		break;
+	if (LIKELY(capa > 0)) {
+	    while (total > capa) {
+		if (capa > LONG_MAX / 2) {
+		    capa = (total + 4095) / 4096 * 4096;
+		    break;
+		}
+		capa = 2 * capa;
 	    }
-	    capa = 2 * capa;
+	}
+	else {
+	    capa = total;
 	}
 	RESIZE_CAPA_TERM(str, capa, termlen);
 	sptr = RSTRING_PTR(str);

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