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RubyVM::InstructionSequence

The InstructionSequence class represents a compiled sequence of instructions for the Ruby Virtual Machine.

With it, you can get a handle to the instructions that make up a method or a proc, compile strings of Ruby code down to VM instructions, and disassemble instruction sequences to strings for easy inspection. It is mostly useful if you want to learn how the Ruby VM works, but it also lets you control various settings for the Ruby iseq compiler.

You can find the source for the VM instructions in insns.def in the Ruby source.

The instruction sequence results will almost certainly change as Ruby changes, so example output in this documentation may be different from what you see.

Public Class Methods

compile(source[, file[, path[, line[, options]]]]) → iseq click to toggle source

Takes source, a String of Ruby code and compiles it to an InstructionSequence.

Optionally takes file, path, and line which describe the filename, absolute path and first line number of the ruby code in source which are metadata attached to the returned iseq.

options, which can be true, false or a Hash, is used to modify the default behavior of the Ruby iseq compiler.

For details regarding valid compile options see ::compile_option=.

RubyVM::InstructionSequence.compile("a = 1 + 2")
#=> <RubyVM::InstructionSequence:<compiled>@<compiled>>
 
               static VALUE
iseqw_s_compile(int argc, VALUE *argv, VALUE self)
{
    VALUE src, file = Qnil, path = Qnil, line = INT2FIX(1), opt = Qnil;
    int i;

    rb_secure(1);

    i = rb_scan_args(argc, argv, "1*:", &src, NULL, &opt);
    if (i > 4+NIL_P(opt)) rb_error_arity(argc, 1, 5);
    switch (i) {
      case 5: opt = argv[--i];
      case 4: line = argv[--i];
      case 3: path = argv[--i];
      case 2: file = argv[--i];
    }
    if (NIL_P(file)) file = rb_fstring_cstr("<compiled>");
    if (NIL_P(line)) line = INT2FIX(1);

    return iseqw_new(rb_iseq_compile_with_option(src, file, path, line, 0, opt));
}
            
compile_file(file[, options]) → iseq click to toggle source

Takes file, a String with the location of a Ruby source file, reads, parses and compiles the file, and returns iseq, the compiled InstructionSequence with source location metadata set.

Optionally takes options, which can be true, false or a Hash, to modify the default behavior of the Ruby iseq compiler.

For details regarding valid compile options see ::compile_option=.

# /tmp/hello.rb
puts "Hello, world!"

# elsewhere
RubyVM::InstructionSequence.compile_file("/tmp/hello.rb")
#=> <RubyVM::InstructionSequence:<main>@/tmp/hello.rb>
 
               static VALUE
iseqw_s_compile_file(int argc, VALUE *argv, VALUE self)
{
    VALUE file, line = INT2FIX(1), opt = Qnil;
    VALUE parser, f, exc = Qnil;
    NODE *node;
    rb_compile_option_t option;
    int i;

    rb_secure(1);
    i = rb_scan_args(argc, argv, "1*:", &file, NULL, &opt);
    if (i > 1+NIL_P(opt)) rb_error_arity(argc, 1, 2);
    switch (i) {
      case 2: opt = argv[--i];
    }
    FilePathValue(file);
    file = rb_fstring(file); /* rb_io_t->pathv gets frozen anyways */

    f = rb_file_open_str(file, "r");

    parser = rb_parser_new();
    rb_parser_set_context(parser, NULL, FALSE);
    node = rb_parser_compile_file_path(parser, file, f, NUM2INT(line));
    if (!node) exc = GET_THREAD()->errinfo;

    rb_io_close(f);
    if (!node) rb_exc_raise(exc);

    make_compile_option(&option, opt);

    return iseqw_new(rb_iseq_new_with_opt(node, rb_fstring_cstr("<main>"),
                                          file,
                                          rb_realpath_internal(Qnil, file, 1),
                                          line, NULL, ISEQ_TYPE_TOP, &option));
}
            
compile_option → options click to toggle source

Returns a hash of default options used by the Ruby iseq compiler.

For details, see ::compile_option=.

 
               static VALUE
iseqw_s_compile_option_get(VALUE self)
{
    return make_compile_option_value(&COMPILE_OPTION_DEFAULT);
}
            
compile_option = options click to toggle source

Sets the default values for various optimizations in the Ruby iseq compiler.

Possible values for options include true, which enables all options, false which disables all options, and nil which leaves all options unchanged.

You can also pass a Hash of options that you want to change, any options not present in the hash will be left unchanged.

Possible option names (which are keys in options) which can be set to true or false include:

  • :inline_const_cache

  • :instructions_unification

  • :operands_unification

  • :peephole_optimization

  • :specialized_instruction

  • :stack_caching

  • :tailcall_optimization

  • :trace_instruction

Additionally, :debug_level can be set to an integer.

These default options can be overwritten for a single run of the iseq compiler by passing any of the above values as the options parameter to ::new, ::compile and ::compile_file.

 
               static VALUE
iseqw_s_compile_option_set(VALUE self, VALUE opt)
{
    rb_compile_option_t option;
    rb_secure(1);
    make_compile_option(&option, opt);
    COMPILE_OPTION_DEFAULT = option;
    return opt;
}
            
disasm(body) → str click to toggle source
disassemble(body) → str

Takes body, a Method or Proc object, and returns a String with the human readable instructions for body.

For a Method object:

# /tmp/method.rb
def hello
  puts "hello, world"
end

puts RubyVM::InstructionSequence.disasm(method(:hello))

Produces:

== disasm: <RubyVM::InstructionSequence:hello@/tmp/method.rb>============
0000 trace            8                                               (   1)
0002 trace            1                                               (   2)
0004 putself
0005 putstring        "hello, world"
0007 send             :puts, 1, nil, 8, <ic:0>
0013 trace            16                                              (   3)
0015 leave                                                            (   2)

For a Proc:

# /tmp/proc.rb
p = proc { num = 1 + 2 }
puts RubyVM::InstructionSequence.disasm(p)

Produces:

== disasm: <RubyVM::InstructionSequence:block in <main>@/tmp/proc.rb>===
== catch table
| catch type: redo   st: 0000 ed: 0012 sp: 0000 cont: 0000
| catch type: next   st: 0000 ed: 0012 sp: 0000 cont: 0012
|------------------------------------------------------------------------
local table (size: 2, argc: 0 [opts: 0, rest: -1, post: 0, block: -1] s1)
[ 2] num
0000 trace            1                                               (   1)
0002 putobject        1
0004 putobject        2
0006 opt_plus         <ic:1>
0008 dup
0009 setlocal         num, 0
0012 leave
 
               static VALUE
iseqw_s_disasm(VALUE klass, VALUE body)
{
    VALUE iseqw = iseqw_s_of(klass, body);
    return NIL_P(iseqw) ? Qnil : rb_iseq_disasm(iseqw_check(iseqw));
}
            
disasm(body) → str click to toggle source
disassemble(body) → str

Takes body, a Method or Proc object, and returns a String with the human readable instructions for body.

For a Method object:

# /tmp/method.rb
def hello
  puts "hello, world"
end

puts RubyVM::InstructionSequence.disasm(method(:hello))

Produces:

== disasm: <RubyVM::InstructionSequence:hello@/tmp/method.rb>============
0000 trace            8                                               (   1)
0002 trace            1                                               (   2)
0004 putself
0005 putstring        "hello, world"
0007 send             :puts, 1, nil, 8, <ic:0>
0013 trace            16                                              (   3)
0015 leave                                                            (   2)

For a Proc:

# /tmp/proc.rb
p = proc { num = 1 + 2 }
puts RubyVM::InstructionSequence.disasm(p)

Produces:

== disasm: <RubyVM::InstructionSequence:block in <main>@/tmp/proc.rb>===
== catch table
| catch type: redo   st: 0000 ed: 0012 sp: 0000 cont: 0000
| catch type: next   st: 0000 ed: 0012 sp: 0000 cont: 0012
|------------------------------------------------------------------------
local table (size: 2, argc: 0 [opts: 0, rest: -1, post: 0, block: -1] s1)
[ 2] num
0000 trace            1                                               (   1)
0002 putobject        1
0004 putobject        2
0006 opt_plus         <ic:1>
0008 dup
0009 setlocal         num, 0
0012 leave
 
               static VALUE
iseqw_s_disasm(VALUE klass, VALUE body)
{
    VALUE iseqw = iseqw_s_of(klass, body);
    return NIL_P(iseqw) ? Qnil : rb_iseq_disasm(iseqw_check(iseqw));
}
            
RubyVM::InstructionSequence.load_from_binary(binary) → iseq click to toggle source

Load an iseq object from binary format String object created by #to_binary.

This loader does not have a verifier, so that loading broken/modified binary causes critical problem.

You should not load binary data provided by others. You should use binary data translated by yourself.

 
               static VALUE
iseqw_s_load_from_binary(VALUE self, VALUE str)
{
    return iseqw_new(iseq_ibf_load(str));
}
            
RubyVM::InstructionSequence.load_from_binary_extra_data(binary) → str click to toggle source

Load extra data embed into binary format String object.

 
               static VALUE
iseqw_s_load_from_binary_extra_data(VALUE self, VALUE str)
{
    return  iseq_ibf_load_extra_data(str);
}
            
new(source[, file[, path[, line[, options]]]]) → iseq click to toggle source

Takes source, a String of Ruby code and compiles it to an InstructionSequence.

Optionally takes file, path, and line which describe the filename, absolute path and first line number of the ruby code in source which are metadata attached to the returned iseq.

options, which can be true, false or a Hash, is used to modify the default behavior of the Ruby iseq compiler.

For details regarding valid compile options see ::compile_option=.

RubyVM::InstructionSequence.compile("a = 1 + 2")
#=> <RubyVM::InstructionSequence:<compiled>@<compiled>>
 
               static VALUE
iseqw_s_compile(int argc, VALUE *argv, VALUE self)
{
    VALUE src, file = Qnil, path = Qnil, line = INT2FIX(1), opt = Qnil;
    int i;

    rb_secure(1);

    i = rb_scan_args(argc, argv, "1*:", &src, NULL, &opt);
    if (i > 4+NIL_P(opt)) rb_error_arity(argc, 1, 5);
    switch (i) {
      case 5: opt = argv[--i];
      case 4: line = argv[--i];
      case 3: path = argv[--i];
      case 2: file = argv[--i];
    }
    if (NIL_P(file)) file = rb_fstring_cstr("<compiled>");
    if (NIL_P(line)) line = INT2FIX(1);

    return iseqw_new(rb_iseq_compile_with_option(src, file, path, line, 0, opt));
}
            
of(p1) click to toggle source

Returns the instruction sequence containing the given proc or method.

For example, using irb:

# a proc
> p = proc { num = 1 + 2 }
> RubyVM::InstructionSequence.of(p)
> #=> <RubyVM::InstructionSequence:block in irb_binding@(irb)>

# for a method
> def foo(bar); puts bar; end
> RubyVM::InstructionSequence.of(method(:foo))
> #=> <RubyVM::InstructionSequence:foo@(irb)>

Using ::compile_file:

# /tmp/iseq_of.rb
def hello
  puts "hello, world"
end

$a_global_proc = proc { str = 'a' + 'b' }

# in irb
> require '/tmp/iseq_of.rb'

# first the method hello
> RubyVM::InstructionSequence.of(method(:hello))
> #=> #<RubyVM::InstructionSequence:0x007fb73d7cb1d0>

# then the global proc
> RubyVM::InstructionSequence.of($a_global_proc)
> #=> #<RubyVM::InstructionSequence:0x007fb73d7caf78>
 
               static VALUE
iseqw_s_of(VALUE klass, VALUE body)
{
    const rb_iseq_t *iseq = NULL;

    rb_secure(1);

    if (rb_obj_is_proc(body)) {
        iseq = vm_proc_iseq(body);

        if (!rb_obj_is_iseq((VALUE)iseq)) {
            iseq = NULL;
        }
    }
    else {
        iseq = rb_method_iseq(body);
    }

    return iseq ? iseqw_new(iseq) : Qnil;
}
            

Public Instance Methods

absolute_path() click to toggle source

Returns the absolute path of this instruction sequence.

nil if the iseq was evaluated from a string.

For example, using ::compile_file:

# /tmp/method.rb
def hello
  puts "hello, world"
end

# in irb
> iseq = RubyVM::InstructionSequence.compile_file('/tmp/method.rb')
> iseq.absolute_path #=> /tmp/method.rb
 
               static VALUE
iseqw_absolute_path(VALUE self)
{
    return rb_iseq_absolute_path(iseqw_check(self));
}
            
base_label() click to toggle source

Returns the base label of this instruction sequence.

For example, using irb:

iseq = RubyVM::InstructionSequence.compile('num = 1 + 2')
#=> <RubyVM::InstructionSequence:<compiled>@<compiled>>
iseq.base_label
#=> "<compiled>"

Using ::compile_file:

# /tmp/method.rb
def hello
  puts "hello, world"
end

# in irb
> iseq = RubyVM::InstructionSequence.compile_file('/tmp/method.rb')
> iseq.base_label #=> <main>
 
               static VALUE
iseqw_base_label(VALUE self)
{
    return rb_iseq_base_label(iseqw_check(self));
}
            
disasm → str click to toggle source

Returns the instruction sequence as a String in human readable form.

puts RubyVM::InstructionSequence.compile('1 + 2').disasm

Produces:

== disasm: <RubyVM::InstructionSequence:<compiled>@<compiled>>==========
0000 trace            1                                               (   1)
0002 putobject        1
0004 putobject        2
0006 opt_plus         <ic:1>
0008 leave
 
               static VALUE
iseqw_disasm(VALUE self)
{
    return rb_iseq_disasm(iseqw_check(self));
}
            
disassemble → str click to toggle source

Returns the instruction sequence as a String in human readable form.

puts RubyVM::InstructionSequence.compile('1 + 2').disasm

Produces:

== disasm: <RubyVM::InstructionSequence:<compiled>@<compiled>>==========
0000 trace            1                                               (   1)
0002 putobject        1
0004 putobject        2
0006 opt_plus         <ic:1>
0008 leave
 
               static VALUE
iseqw_disasm(VALUE self)
{
    return rb_iseq_disasm(iseqw_check(self));
}
            
eval → obj click to toggle source

Evaluates the instruction sequence and returns the result.

RubyVM::InstructionSequence.compile("1 + 2").eval #=> 3
 
               static VALUE
iseqw_eval(VALUE self)
{
    rb_secure(1);
    return rb_iseq_eval(iseqw_check(self));
}
            
first_lineno() click to toggle source

Returns the number of the first source line where the instruction sequence was loaded from.

For example, using irb:

iseq = RubyVM::InstructionSequence.compile('num = 1 + 2')
#=> <RubyVM::InstructionSequence:<compiled>@<compiled>>
iseq.first_lineno
#=> 1
 
               static VALUE
iseqw_first_lineno(VALUE self)
{
    return rb_iseq_first_lineno(iseqw_check(self));
}
            
inspect() click to toggle source

Returns a human-readable string representation of this instruction sequence, including the label and path.

 
               static VALUE
iseqw_inspect(VALUE self)
{
    const rb_iseq_t *iseq = iseqw_check(self);

    if (!iseq->body->location.label) {
        return rb_sprintf("#<%s: uninitialized>", rb_obj_classname(self));
    }
    else {
        return rb_sprintf("<%s:%s@%s>",
                          rb_obj_classname(self),
                          RSTRING_PTR(iseq->body->location.label), RSTRING_PTR(iseq->body->location.path));
    }
}
            
label() click to toggle source

Returns the label of this instruction sequence.

<main> if it's at the top level, <compiled> if it was evaluated from a string.

For example, using irb:

iseq = RubyVM::InstructionSequence.compile('num = 1 + 2')
#=> <RubyVM::InstructionSequence:<compiled>@<compiled>>
iseq.label
#=> "<compiled>"

Using ::compile_file:

# /tmp/method.rb
def hello
  puts "hello, world"
end

# in irb
> iseq = RubyVM::InstructionSequence.compile_file('/tmp/method.rb')
> iseq.label #=> <main>
 
               static VALUE
iseqw_label(VALUE self)
{
    return rb_iseq_label(iseqw_check(self));
}
            
line_trace_all() click to toggle source

Experimental MRI specific feature, only available as C level api.

Returns all specified_line events.

 
               VALUE
rb_iseqw_line_trace_all(VALUE iseqw)
{
    VALUE result = rb_ary_new();
    rb_iseqw_line_trace_each(iseqw, collect_trace, (void *)result);
    return result;
}
            
line_trace_specify(p1, p2) click to toggle source

Experimental MRI specific feature, only available as C level api.

Set a specified_line event at the given line position, if the set parameter is true.

This method is useful for building a debugger breakpoint at a specific line.

A TypeError is raised if set is not boolean.

If pos is a negative integer a TypeError exception is raised.

 
               VALUE
rb_iseqw_line_trace_specify(VALUE iseqval, VALUE pos, VALUE set)
{
    struct set_specifc_data data;

    data.prev = 0;
    data.pos = NUM2INT(pos);
    if (data.pos < 0) rb_raise(rb_eTypeError, "`pos' is negative");

    switch (set) {
      case Qtrue:  data.set = 1; break;
      case Qfalse: data.set = 0; break;
      default:
        rb_raise(rb_eTypeError, "`set' should be true/false");
    }

    rb_iseqw_line_trace_each(iseqval, line_trace_specify, (void *)&data);

    if (data.prev == 0) {
        rb_raise(rb_eTypeError, "`pos' is out of range.");
    }
    return data.prev == 1 ? Qtrue : Qfalse;
}
            
path() click to toggle source

Returns the path of this instruction sequence.

<compiled> if the iseq was evaluated from a string.

For example, using irb:

iseq = RubyVM::InstructionSequence.compile('num = 1 + 2')
#=> <RubyVM::InstructionSequence:<compiled>@<compiled>>
iseq.path
#=> "<compiled>"

Using ::compile_file:

# /tmp/method.rb
def hello
  puts "hello, world"
end

# in irb
> iseq = RubyVM::InstructionSequence.compile_file('/tmp/method.rb')
> iseq.path #=> /tmp/method.rb
 
               static VALUE
iseqw_path(VALUE self)
{
    return rb_iseq_path(iseqw_check(self));
}
            
to_a → ary click to toggle source

Returns an Array with 14 elements representing the instruction sequence with the following data:

magic

A string identifying the data format. Always YARVInstructionSequence/SimpleDataFormat.

major_version

The major version of the instruction sequence.

minor_version

The minor version of the instruction sequence.

format_type

A number identifying the data format. Always 1.

misc

A hash containing:

:arg_size

the total number of arguments taken by the method or the block (0 if iseq doesn’t represent a method or block)

:local_size

the number of local variables + 1

:stack_max

used in calculating the stack depth at which a SystemStackError is thrown.

label

The name of the context (block, method, class, module, etc.) that this instruction sequence belongs to.

<main> if it's at the top level, <compiled> if it was evaluated from a string.

path

The relative path to the Ruby file where the instruction sequence was loaded from.

<compiled> if the iseq was evaluated from a string.

absolute_path

The absolute path to the Ruby file where the instruction sequence was loaded from.

nil if the iseq was evaluated from a string.

first_lineno

The number of the first source line where the instruction sequence was loaded from.

type

The type of the instruction sequence.

Valid values are :top, :method, :block, :class, :rescue, :ensure, :eval, :main, and :defined_guard.

locals

An array containing the names of all arguments and local variables as symbols.

params

An Hash object containing parameter information.

More info about these values can be found in vm_core.h.

catch_table

A list of exceptions and control flow operators (rescue, next, redo, break, etc.).

bytecode

An array of arrays containing the instruction names and operands that make up the body of the instruction sequence.

Note that this format is MRI specific and version dependent.

 
               static VALUE
iseqw_to_a(VALUE self)
{
    const rb_iseq_t *iseq = iseqw_check(self);
    rb_secure(1);
    return iseq_data_to_ary(iseq);
}
            
to_binary(extra_data = nil) → binary str click to toggle source

Returns serialized iseq binary format data as a String object. A corresponding iseq object is created by ::load_from_binary method.

String extra_data will be saved with binary data. You can access this data with ::load_from_binary_extra_data.

Note that the translated binary data is not portable. You can not move this binary data to another machine. You can not use the binary data which is created by another version/another architecture of Ruby.

 
               static VALUE
iseqw_to_binary(int argc, VALUE *argv, VALUE self)
{
    VALUE opt;
    rb_scan_args(argc, argv, "01", &opt);
    return iseq_ibf_dump(iseqw_check(self), opt);
}