[PATCH 01/11] introduce new str_new_dd_freeze internal function

[Eric Wong <e@80x24.org>]

This seems like it will be a common pattern to create
and immediately dedupe a string.  In the future, we may
be able to save some memory by eliding temporary object
creation or releasing heap memory via rb_str_resize(..., 0)
---
 ext/kcar/extconf.rb | 15 ++++++++++-----
 ext/kcar/kcar.rl    |  9 +++++++--
 2 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/ext/kcar/extconf.rb b/ext/kcar/extconf.rb
index 89ac586..b65846a 100644
--- a/ext/kcar/extconf.rb
+++ b/ext/kcar/extconf.rb
@@ -6,15 +6,20 @@ dir_config("kcar")
 have_macro("SIZEOF_OFF_T", "ruby.h") or check_sizeof("off_t", "sys/types.h")
 have_macro("SIZEOF_LONG", "ruby.h") or check_sizeof("long", "sys/types.h")
 
-uminus_dedupe = false
+message('checking if String#-@ (str_uminus) dedupes... ')
 begin
-  # oddly, opt_str_freeze is not always effective:
-  # https://bugs.ruby-lang.org/issues/13282
   a = -(%w(t e s t).join)
   b = -(%w(t e s t).join)
-  uminus_dedupe = a.object_id == b.object_id
+  if a.equal?(b)
+    $CPPFLAGS += " -DSTR_UMINUS_DEDUPE=1 "
+    message("yes\n")
+  else
+    $CPPFLAGS += " -DSTR_UMINUS_DEDUPE=0 "
+    message("no, needs Ruby 2.5+\n")
+  end
 rescue NoMethodError
+  $CPPFLAGS += " -DSTR_UMINUS_DEDUPE=0 "
+  message("no, String#-@ not available\n")
 end
-$CFLAGS += " -DSTR_UMINUS_DEDUPE=#{uminus_dedupe ? 1 : 0}"
 
 create_makefile("kcar_ext")
diff --git a/ext/kcar/kcar.rl b/ext/kcar/kcar.rl
index cbcfa97..79f65db 100644
--- a/ext/kcar/kcar.rl
+++ b/ext/kcar/kcar.rl
@@ -106,6 +106,11 @@ static VALUE str_dd_freeze(VALUE str)
   return str;
 }
 
+static VALUE str_new_dd_freeze(const char *ptr, long len)
+{
+  return str_dd_freeze(rb_str_new(ptr, len));
+}
+
 static VALUE stripped_str_new(const char *str, long len)
 {
   long end;
@@ -161,7 +166,7 @@ status_phrase(struct http_parser *hp, VALUE hdr, const char *ptr, size_t len)
 {
   long nr;
 
-  hp->status = str_dd_freeze(rb_str_new(ptr, len));
+  hp->status = str_new_dd_freeze(ptr, len);
 
   /* RSTRING_PTR is null terminated, ptr is not */
   nr = strtol(RSTRING_PTR(hp->status), NULL, 10);
@@ -238,7 +243,7 @@ static void write_value(VALUE hdr, struct http_parser *hp,
   vlen = LEN(mark, p);
   VALIDATE_MAX_LENGTH(vlen, FIELD_VALUE);
   VALIDATE_MAX_LENGTH(flen, FIELD_NAME);
-  f = str_dd_freeze(rb_str_new(fptr, (long)flen));
+  f = str_new_dd_freeze(fptr, (long)flen);
   v = stripped_str_new(vptr, (long)vlen);
 
   /* needs more tests for error-checking here */