Stop allocating backref strings within gsub's search loop

* internal.h: add prototype for rb_reg_search0

* re.c: rename rb_reg_search to rb_reg_search0, add set_backref_str
  argument to allow callers to indicate that they don't require the
  backref string to be allocated

* string.c: don't allocate backref str if replacement string is provided

Closes GH-578. [Bug #9676] [ruby-core:61682]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45414 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 5 insertions, 3 deletions

diff --git a/string.c b/string.c
index 075876f47a..3eda81ca3c 100644
--- a/string.c
+++ b/string.c
@@ -4021,6 +4021,7 @@ str_gsub(int argc, VALUE *argv, VALUE str, int bang)
     int iter = 0;
     char *sp, *cp;
     int tainted = 0;
+    int str_replace;
     rb_encoding *str_enc;
 
     switch (argc) {
@@ -4041,7 +4042,8 @@ str_gsub(int argc, VALUE *argv, VALUE str, int bang)
     }
 
     pat = get_pat(argv[0], 1);
-    beg = rb_reg_search(pat, str, 0, 0);
+    str_replace = !iter && NIL_P(hash);
+    beg = rb_reg_search0(pat, str, 0, 0, !str_replace);
     if (beg < 0) {
 	if (bang) return Qnil;	/* no match, no substitution */
 	return rb_str_dup(str);
@@ -4064,7 +4066,7 @@ str_gsub(int argc, VALUE *argv, VALUE str, int bang)
 	regs = RMATCH_REGS(match);
 	beg0 = BEG(0);
 	end0 = END(0);
-	if (iter || !NIL_P(hash)) {
+	if (!str_replace) {
             if (iter) {
                 val = rb_obj_as_string(rb_yield(rb_reg_nth_match(0, match)));
             }
@@ -4104,7 +4106,7 @@ str_gsub(int argc, VALUE *argv, VALUE str, int bang)
 	}
 	cp = RSTRING_PTR(str) + offset;
 	if (offset > RSTRING_LEN(str)) break;
-	beg = rb_reg_search(pat, str, offset, 0);
+	beg = rb_reg_search0(pat, str, offset, 0, !str_replace);
     } while (beg >= 0);
     if (RSTRING_LEN(str) > offset) {
         rb_enc_str_buf_cat(dest, cp, RSTRING_LEN(str) - offset, str_enc);