string.c: shrink too big buffer

* string.c (rb_str_resize): shrink the buffer even if new length
  is same but it is enough smaller than the capacity.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@46408 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

Conflicts:
	string.c

Author: nobu

string.c

@@ -2034,9 +2034,11 @@ rb_str_resize(VALUE str, long len)
     independent = str_independent(str);
     ENC_CODERANGE_CLEAR(str);
     slen = RSTRING_LEN(str);
-    if (len != slen) {
+
+    {
 	const int termlen = TERM_LEN(str);
 	if (STR_EMBED_P(str)) {
+	    if (len == slen) return str;
 	    if (len + termlen <= RSTRING_EMBED_LEN_MAX + 1) {
 		STR_SET_EMBED_LEN(str, len);
 		TERM_FILL(RSTRING(str)->as.ary + len, termlen);
@@ -2056,11 +2058,13 @@ rb_str_resize(VALUE str, long len)
 	    return str;
 	}
 	else if (!independent) {
+	    if (len == slen) return str;
 	    str_make_independent_expand(str, len - slen);
 	}
 	else if (slen < len || slen - len > 1024) {
 	    REALLOC_N(RSTRING(str)->as.heap.ptr, char, len + termlen);
 	}
+	else if (len == slen) return str;
 	if (!STR_NOCAPA_P(str)) {
 	    RSTRING(str)->as.heap.aux.capa = len;
 	}