time.c (time_strftime): avoid garbage in common case

strftime format strings which are dynamically-generated will benefit
from avoiding garbage, here.

* time.c (time_strftime): use rb_str_tmp_frozen_{acquire,release}
* test/ruby/test_time.rb (test_strftime_no_hidden_garbage): new test

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@57476 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 5 insertions, 3 deletions

diff --git a/time.c b/time.c
index 30bb371781..0d93ec65ff 100644
--- a/time.c
+++ b/time.c
@@ -4422,6 +4422,7 @@ time_strftime(VALUE time, VALUE format)
     const char *fmt;
     long len;
     rb_encoding *enc;
+    VALUE tmp;
 
     GetTimeval(time, tobj);
     MAKE_TM(time, tobj);
@@ -4429,9 +4430,9 @@ time_strftime(VALUE time, VALUE format)
     if (!rb_enc_str_asciicompat_p(format)) {
 	rb_raise(rb_eArgError, "format should have ASCII compatible encoding");
     }
-    format = rb_str_new4(format);
-    fmt = RSTRING_PTR(format);
-    len = RSTRING_LEN(format);
+    tmp = rb_str_tmp_frozen_acquire(format);
+    fmt = RSTRING_PTR(tmp);
+    len = RSTRING_LEN(tmp);
     enc = rb_enc_get(format);
     if (len == 0) {
 	rb_warning("strftime called with empty format string");
@@ -4440,6 +4441,7 @@ time_strftime(VALUE time, VALUE format)
     else {
 	VALUE str = rb_strftime_alloc(fmt, len, enc, &tobj->vtm, tobj->timew,
 				      TIME_UTC_P(tobj));
+	rb_str_tmp_frozen_release(format, tmp);
 	if (!str) rb_raise(rb_eArgError, "invalid format: %"PRIsVALUE, format);
 	return str;
     }