gistfile1.txt

The "tostring" instruction below calls into this C code, from string.c. This checks if the expression/object is already a string, and does nothing if it is. If it's not a string, it calls "to_s" on the object.

VALUE
rb_obj_as_string(VALUE obj)
{
    VALUE str;

    if (RB_TYPE_P(obj, T_STRING)) {
	return obj;
    }
    str = rb_funcall(obj, id_to_s, 0);
    if (!RB_TYPE_P(str, T_STRING))
	return rb_any_to_s(obj);
    if (OBJ_TAINTED(obj)) OBJ_TAINT(str);
    return str;
}

Ruby code:

a = 1
b = 2
puts "This is the sum: #{a+b}"

YARV instructions:


== disasm: <RubyVM::InstructionSequence:<main>@self1.rb>================
local table (size: 3, argc: 0 [opts: 0, rest: -1, post: 0, block: -1] s1)
[ 3] a          [ 2] b          
0000 trace            1                                               (   3)
0002 putobject        1
0004 setdynamic       a, 0
0007 trace            1                                               (   4)
0009 putobject        2
0011 setdynamic       b, 0
0014 trace            1                                               (   5)
0016 putself          
0017 putobject        "This is the sum: "
0019 getdynamic       a, 0
0022 getdynamic       b, 0
0025 opt_plus         <ic:2>
0027 tostring         
0028 concatstrings    2
0030 send             :puts, 1, nil, 8, <ic:1>
0036 leave