diff --git a/ChangeLog b/ChangeLog
index b8dffe35a0..cd49e10372 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Tue Sep  3 22:03:49 2013  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* string.c (rb_enc_str_new_cstr): new function to create a string from
+	  the C-string pointer with the specified encoding.
+
 Tue Sep  3 21:41:37 2013  Akira Matsuda  <ronnie@dio.jp>
 
 	* eval.c (Init_eval): Make Module#include and Module#prepend public
diff --git a/README.EXT b/README.EXT
index dc3136c414..09354a149b 100644
--- a/README.EXT
+++ b/README.EXT
@@ -218,6 +218,7 @@ rb_str_vcatf(VALUE str, const char* format, va_list ap) ::
   rb_str_cat2(str, rb_vsprintf(format, ap)), respectively.
 
 rb_enc_str_new(const char *ptr, long len, rb_encoding *enc) ::
+rb_enc_str_new_cstr(const char *ptr, rb_encoding *enc) ::
 
   Creates a new Ruby string with the specified encoding.
 
diff --git a/README.EXT.ja b/README.EXT.ja
index cd7fda5a4f..d4d1e61980 100644
--- a/README.EXT.ja
+++ b/README.EXT.ja
@@ -245,6 +245,7 @@ rb_str_vcatf(VALUE str, const char* format, va_list ap)
   rb_str_cat2(str, rb_vsprintf(format, ap)) と同等である．
 
 rb_enc_str_new(const char *ptr, long len, rb_encoding *enc)
+rb_enc_str_new_cstr(const char *ptr, rb_encoding *enc)
 
   指定されたエンコーディングでRubyの文字列を生成する.
 
diff --git a/include/ruby/encoding.h b/include/ruby/encoding.h
index ebd9cfd262..e0dc66dec7 100644
--- a/include/ruby/encoding.h
+++ b/include/ruby/encoding.h
@@ -89,6 +89,7 @@ VALUE rb_enc_associate(VALUE, rb_encoding*);
 void rb_enc_copy(VALUE dst, VALUE src);
 
 VALUE rb_enc_str_new(const char*, long, rb_encoding*);
+VALUE rb_enc_str_new_cstr(const char*, rb_encoding*);
 VALUE rb_enc_reg_new(const char*, long, rb_encoding*, int);
 PRINTF_ARGS(VALUE rb_enc_sprintf(rb_encoding *, const char*, ...), 2, 3);
 VALUE rb_enc_vsprintf(rb_encoding *, const char*, va_list);
@@ -103,6 +104,15 @@ VALUE rb_str_export_to_enc(VALUE, rb_encoding *);
 VALUE rb_str_conv_enc(VALUE str, rb_encoding *from, rb_encoding *to);
 VALUE rb_str_conv_enc_opts(VALUE str, rb_encoding *from, rb_encoding *to, int ecflags, VALUE ecopts);
 
+#if defined(__GNUC__) && !defined(__PCC__)
+#define rb_enc_str_new_cstr(str, enc) __extension__ (	\
+{					       \
+    (__builtin_constant_p(str)) ?	       \
+	rb_enc_str_new((str), (long)strlen(str), (enc)) : \
+	rb_enc_str_new_cstr((str), (enc)); \
+})
+#endif
+
 PRINTF_ARGS(NORETURN(void rb_enc_raise(rb_encoding *, VALUE, const char*, ...)), 3, 4);
 
 /* index -> rb_encoding */
diff --git a/string.c b/string.c
index 7f8707ae5c..70cedf204b 100644
--- a/string.c
+++ b/string.c
@@ -34,6 +34,7 @@
 #undef rb_str_new_cstr
 #undef rb_tainted_str_new_cstr
 #undef rb_usascii_str_new_cstr
+#undef rb_enc_str_new_cstr
 #undef rb_external_str_new_cstr
 #undef rb_locale_str_new_cstr
 #undef rb_str_dup_frozen
@@ -473,6 +474,18 @@ rb_usascii_str_new_cstr(const char *ptr)
     return str;
 }
 
+VALUE
+rb_enc_str_new_cstr(const char *ptr, rb_encoding *enc)
+{
+    if (!ptr) {
+	rb_raise(rb_eArgError, "NULL pointer given");
+    }
+    if (rb_enc_mbminlen(enc) != 1) {
+	rb_raise(rb_eArgError, "wchar encoding given");
+    }
+    return rb_enc_str_new(ptr, strlen(ptr), enc);
+}
+
 VALUE
 rb_tainted_str_new(const char *ptr, long len)
 {