* vm_opts.h, iseq.c, iseq.h: add compile option to force frozen

string literals.
  [Feature #11473]
  This addition is not specification change, but to try frozen
  string literal world discussed on [Feature #11473].
  You can try frozen string literal world using this magical line:
    RubyVM::InstructionSequence.compile_option =
      {frozen_string_literal: true}
  Note that this is a global compilation option, so that you need to
  compile another script like that:
    p 'foo'.frozen? #=> false
    RubyVM::InstructionSequence.compile_option =
      {frozen_string_literal: true}
    p 'foo'.frozen? #=> false, because this line is already compiled.
    p eval("'foo'.frozen?") #=> true
  Details:
    * String literals are deduped by rb_fstring().
    * Dynamic string literals ("...#{xyz}...") is now only frozen,
      not deduped. Maybe you have other ideas.
  Now, please do not use this option on your productions :)
  Of course, current specification can be changed.
* compile.c: ditto.
* test/ruby/test_iseq.rb: add a test.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@51659 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,38 @@
+Sat Aug 22 05:31:37 2015  Koichi Sasada  <ko1@atdot.net>
+
+	* vm_opts.h, iseq.c, iseq.h: add compile option to force frozen
+	  string literals.
+	  [Feature #11473]
+
+	  This addition is not specification change, but to try frozen
+	  string literal world discussed on [Feature #11473].
+
+	  You can try frozen string literal world using this magical line:
+
+	    RubyVM::InstructionSequence.compile_option =
+	      {frozen_string_literal: true}
+
+	  Note that this is a global compilation option, so that you need to
+	  compile another script like that:
+
+	    p 'foo'.frozen? #=> false
+	    RubyVM::InstructionSequence.compile_option =
+	      {frozen_string_literal: true}
+	    p 'foo'.frozen? #=> false, because this line is already compiled.
+	    p eval("'foo'.frozen?") #=> true
+
+	  Details:
+	    * String literals are deduped by rb_fstring().
+	    * Dynamic string literals ("...#{xyz}...") is now only frozen,
+	      not deduped. Maybe you have other ideas.
+
+	  Now, please do not use this option on your productions :)
+	  Of course, current specification can be changed.
+
+	* compile.c: ditto.
+
+	* test/ruby/test_iseq.rb: add a test.
+
 Sat Aug 22 02:53:12 2015  Aaron Patterson <tenderlove@ruby-lang.org>
 
 	* ext/psych/*: update to Psych 2.0.14

compile.c

@@ -5002,10 +5002,15 @@ iseq_compile_each(rb_iseq_t *iseq, LINK_ANCHOR *ret, NODE * node, int poped)
 	break;
       }
       case NODE_STR:{
-	node->nd_lit = rb_fstring(node->nd_lit);
 	debugp_param("nd_lit", node->nd_lit);
 	if (!poped) {
-	    ADD_INSN1(ret, line, putstring, node->nd_lit);
+	    node->nd_lit = rb_fstring(node->nd_lit);
+	    if (iseq->compile_data->option->frozen_string_literal) {
+		ADD_INSN1(ret, line, putobject, node->nd_lit); /* already frozen */
+	    }
+	    else {
+		ADD_INSN1(ret, line, putstring, node->nd_lit);
+	    }
 	}
 	break;
       }
@@ -5015,6 +5020,11 @@ iseq_compile_each(rb_iseq_t *iseq, LINK_ANCHOR *ret, NODE * node, int poped)
 	if (poped) {
 	    ADD_INSN(ret, line, pop);
 	}
+	else {
+	    if (iseq->compile_data->option->frozen_string_literal) {
+		ADD_SEND (ret, line, idFreeze, INT2FIX(0));
+	    }
+	}
 	break;
       }
       case NODE_XSTR:{

iseq.c

@@ -338,7 +338,9 @@ static rb_compile_option_t COMPILE_OPTION_DEFAULT = {
     OPT_INSTRUCTIONS_UNIFICATION, /* int instructions_unification; */
     OPT_STACK_CACHING, /* int stack_caching; */
     OPT_TRACE_INSTRUCTION, /* int trace_instruction */
+    OPT_FROZEN_STRING_LITERAL
 };
+
 static const rb_compile_option_t COMPILE_OPTION_FALSE = {0};
 
 static void
@@ -375,6 +377,7 @@ make_compile_option(rb_compile_option_t *option, VALUE opt)
 	SET_COMPILE_OPTION(option, opt, instructions_unification);
 	SET_COMPILE_OPTION(option, opt, stack_caching);
 	SET_COMPILE_OPTION(option, opt, trace_instruction);
+	SET_COMPILE_OPTION(option, opt, frozen_string_literal);
 	SET_COMPILE_OPTION_NUM(option, opt, debug_level);
 #undef SET_COMPILE_OPTION
 #undef SET_COMPILE_OPTION_NUM

iseq.h

@@ -61,6 +61,7 @@ struct rb_compile_option_struct {
     int instructions_unification;
     int stack_caching;
     int trace_instruction;
+    int frozen_string_literal;
     int debug_level;
 };
 

test/ruby/test_iseq.rb

@@ -141,4 +141,17 @@ class TestISeq < Test::Unit::TestCase
     assert_raise(TypeError, bug11159) {ISeq.compile(:foo)}
     assert_raise(TypeError, bug11159) {ISeq.compile(1)}
   end
+
+  def test_frozen_string_literal_compile_option
+    $f = 'f'
+    line = __LINE__ + 2
+    code = <<-'EOS'
+    ['foo', 'foo', "#{$f}foo"]
+    EOS
+    s1, s2, s3 = RubyVM::InstructionSequence.compile(code, __FILE__, __FILE__, line, {frozen_string_literal: true}).eval
+    assert(s1.frozen?)
+    assert(s2.frozen?)
+    assert(s3.frozen?)
+    assert(s1.object_id == s2.object_id)
+  end
 end

vm_opts.h

@@ -23,7 +23,7 @@
 #define OPT_PEEPHOLE_OPTIMIZATION    1
 #define OPT_SPECIALISED_INSTRUCTION  1
 #define OPT_INLINE_CONST_CACHE       1
-
+#define OPT_FROZEN_STRING_LITERAL    0
 
 /* Build Options.
  * You can't change these options at runtime.