introduce rb_autoload_str to replace rb_autoload

rb_autoload_str may be safer by preventing premature GC.  It
can also be more efficient by passing a pre-frozen string that
can be deduped using rb_fstring.  Common autoload callers (e.g.
rubygems, rdoc) already use string literals as the file
argument.

There seems to be no reason to expose rb_autoload_str to the
public C API since autoload is not performance-critical.
Applications may declare autoloads in Ruby code or via
rb_funcall; so merely deprecate rb_autoload without exposing
rb_autoload_str to new users.

Running: valgrind -v ruby -rrdoc -rubygems -e exit
shows a minor memory reduction (32-bit userspace)

before:

  in use at exit: 1,600,621 bytes in 28,819 blocks
total heap usage: 55,786 allocs, 26,967 frees, 6,693,790 bytes allocated

after:

  in use at exit: 1,599,778 bytes in 28,789 blocks
total heap usage: 55,739 allocs, 26,950 frees, 6,692,973 bytes allocated

* include/ruby/intern.h (rb_autoload): deprecate
* internal.h (rb_autoload_str): declare
* load.c (rb_mod_autoload): use rb_autoload_str
* variable.c (rb_autoload): become compatibility wrapper
  (rb_autoload_str): hoisted out from old rb_autoload
  [ruby-core:71369] [Feature #11664]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@52909 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,12 @@
+Sun Dec  6 19:52:31 2015  Eric Wong  <e@80x24.org>
+
+	* include/ruby/intern.h (rb_autoload): deprecate
+	* internal.h (rb_autoload_str): declare
+	* load.c (rb_mod_autoload): use rb_autoload_str
+	* variable.c (rb_autoload): become compatibility wrapper
+	  (rb_autoload_str): hoisted out from old rb_autoload
+	  [ruby-core:71369] [Feature #11664]
+
 Sun Dec  6 19:02:55 2015  Kazuhiro NISHIYAMA  <zn@mbf.nifty.com>
 
 	* configure.in: add missing x.

NEWS

@@ -241,6 +241,8 @@ with all sufficient information, see the ChangeLog file.
 * rb_time_timespec_new() is added to create a time object with epoch,
   nanosecond, and UTC/localtime/time offset arguments.  [Feature #11558]
 
+* rb_autoload() deprecated, use rb_funcall() instead.  [Feature #11664]
+
 === Build system updates
 
 === Implementation changes

include/ruby/intern.h

@@ -937,7 +937,7 @@ VALUE rb_path_to_class(VALUE);
 VALUE rb_path2class(const char*);
 void rb_name_class(VALUE, ID);
 VALUE rb_class_name(VALUE);
-void rb_autoload(VALUE, ID, const char*);
+DEPRECATED(void rb_autoload(VALUE, ID, const char*));
 VALUE rb_autoload_load(VALUE, ID);
 VALUE rb_autoload_p(VALUE, ID);
 VALUE rb_f_trace_var(int, const VALUE*);

internal.h

@@ -1205,6 +1205,7 @@ size_t rb_generic_ivar_memsize(VALUE);
 VALUE rb_search_class_path(VALUE);
 VALUE rb_attr_delete(VALUE, ID);
 VALUE rb_ivar_lookup(VALUE obj, ID id, VALUE undef);
+void rb_autoload_str(VALUE mod, ID id, VALUE file);
 
 /* version.c */
 extern const char ruby_engine[];

load.c

@@ -1099,7 +1099,7 @@ rb_mod_autoload(VALUE mod, VALUE sym, VALUE file)
     ID id = rb_to_id(sym);
 
     FilePathValue(file);
-    rb_autoload(mod, id, RSTRING_PTR(file));
+    rb_autoload_str(mod, id, file);
     return Qnil;
 }
 

variable.c

@@ -1915,9 +1915,18 @@ static const rb_data_type_t autoload_data_i_type = {
 
 void
 rb_autoload(VALUE mod, ID id, const char *file)
+{
+    if (!file || !*file) {
+	rb_raise(rb_eArgError, "empty file name");
+    }
+    rb_autoload_str(mod, id, rb_fstring_cstr(file));
+}
+
+void
+rb_autoload_str(VALUE mod, ID id, VALUE file)
 {
     st_data_t av;
-    VALUE ad, fn;
+    VALUE ad;
     struct st_table *tbl;
     struct autoload_data_i *ele;
     rb_const_entry_t *ce;
@@ -1926,7 +1935,9 @@ rb_autoload(VALUE mod, ID id, const char *file)
 	rb_raise(rb_eNameError, "autoload must be constant name: %"PRIsVALUE"",
 		 QUOTE_ID(id));
     }
-    if (!file || !*file) {
+
+    Check_Type(file, T_STRING);
+    if (!RSTRING_LEN(file)) {
 	rb_raise(rb_eArgError, "empty file name");
     }
 
@@ -1947,12 +1958,13 @@ rb_autoload(VALUE mod, ID id, const char *file)
 	RB_OBJ_WRITTEN(mod, Qnil, av);
 	DATA_PTR(av) = tbl = st_init_numtable();
     }
-    fn = rb_str_new2(file);
-    FL_UNSET(fn, FL_TAINT);
-    OBJ_FREEZE(fn);
 
     ad = TypedData_Make_Struct(0, struct autoload_data_i, &autoload_data_i_type, ele);
-    ele->feature = fn;
+    if (OBJ_TAINTED(file)) {
+	file = rb_str_dup(file);
+	FL_UNSET(file, FL_TAINT);
+    }
+    ele->feature = rb_fstring(file);
     ele->safe_level = rb_safe_level();
     ele->value = Qundef;
     ele->state = 0;