From: Adam Strzelecki <ono@...>
Date: 2008-06-12T00:43:10+09:00
Subject: [ruby-core:17220] VM::InstructionSequence to_a->load->to_a != to_a

Hello,

There's apparently a bug in VM::InstructionSequence.load code, coz  
code generated with to_a, loaded back and again to_a is not the same  
as one emitted just with to_a.
Of course label names differ, but also local_size and args_size are  
different for blocks (instructions seems to be OK).

After my initial enthusiasm, I realised that  
VM::InstructionSequence.load doesn't work as it should at all.  
Actually it is not possible to call any function/method with argument  
with current code.

Here's sample test showing the differences:

-----------------------------------------------------
#!/usr/bin/env ruby-1.9
require 'zlib'

code = VM::InstructionSequence.compile_file 'test.rb'

STDOUT.puts code.to_a.inspect.gsub(/, \[/, ",\n\t[")
code = VM::InstructionSequence.load code.to_a

STDERR.puts code.to_a.inspect.gsub(/, \[/, ",\n\t[")
-----------------------------------------------------


I've compared STDOUT & STDERR using samples/test.rb & I got plenty of  
local_size differences like:
-	["YARV", 1, 1, 1, {:arg_size=>1, :local_size=>2, :stack_max=>2},  
"block in <main>", "test.rb", :block,
+	["YARV", 1, 1, 1, {:arg_size=>1, :local_size=>1, :stack_max=>2},  
"block in <main>", "test.rb", :block,

It seems that iseq_build_from_ary @ compile.c is broken, I'm not sure  
about to_a.

I've did some fixes (diff below):

1) Regardless of iseq->type it seems that local_size is always  
local_table_size + 1, also in original code opt (=1) is added twice to  
local_size (= local_table_size = opt + RARRAY_LEN(locals))
2) It should be iseq->arg_opts = RARRAY_LEN(arg_opt_labels)

With those fixes I've managed to limit the differences of to_a->load- 
 >to_a != to_a, but still those are not the same. Also I've managed to  
call methods with args from restored with VM::InstructionSequence.load  
code, but it seems it does works weird (slow + hungs).

Best regards,
-- 
Adam

Index: compile.c
===================================================================
--- compile.c	(revision 17097)
+++ compile.c	(working copy)
@@ -4983,22 +4983,16 @@
  		    VALUE exception, VALUE body)
  {
      int i;
-    int opt = 0;
      ID *tbl;
      struct st_table *labels_table = st_init_numtable();

      DECL_ANCHOR(anchor);

      INIT_ANCHOR(anchor);
-    if (iseq->type == ISEQ_TYPE_METHOD ||
-	iseq->type == ISEQ_TYPE_TOP ||
-	iseq->type == ISEQ_TYPE_CLASS) {
-	opt = 1;
-    }

-    iseq->local_table_size = opt + RARRAY_LEN(locals);
+    iseq->local_table_size = RARRAY_LEN(locals);
      iseq->local_table = tbl = (ID *)ALLOC_N(ID *, iseq- 
 >local_table_size);
-    iseq->local_size = opt + iseq->local_table_size;
+    iseq->local_size = 1 + iseq->local_table_size;

      for (i=0; i<RARRAY_LEN(locals); i++) {
  	VALUE lv = RARRAY_PTR(locals)[i];
@@ -5025,7 +5019,8 @@
  	iseq->arg_post_len = FIX2INT(arg_post_len);
  	iseq->arg_post_start = FIX2INT(arg_post_start);
  	iseq->arg_block = FIX2INT(arg_block);
-	iseq->arg_opt_table = (VALUE *)ALLOC_N(VALUE,  
RARRAY_LEN(arg_opt_labels));
+        iseq->arg_opts = RARRAY_LEN(arg_opt_labels);
+	iseq->arg_opt_table = (VALUE *)ALLOC_N(VALUE, iseq->arg_opts);

  	if (iseq->arg_block != -1) {
  	    iseq->arg_size = iseq->arg_block + 1;
@@ -5037,7 +5032,7 @@
  	    iseq->arg_size = iseq->arg_rest + 1;
  	}
  	else {
-	    iseq->arg_size = iseq->argc + iseq->arg_opts;
+	    iseq->arg_size = iseq->argc + (iseq->arg_opts ? iseq->arg_opts -  
1 : 0);
  	}

  	for (i=0; i<RARRAY_LEN(arg_opt_labels); i++) {