%% Some Erlang expressions:

true.
1+1.
if (X > Y) -> X; true -> Y end.

%% An Erlang function:

max(X, Y) ->
  if (X > Y) -> X;
     true    -> Y
  end.

> erlc foo.erl

1> c(foo).
{ok, foo}

1> compile:file(foo).
{ok, foo}

1> c(foo, [nowarn_unused_function, debug_info]).

1> compile:file(foo, [binary]).
{ok, foo, <<70,79,82,...>>}

1> c(foo, [to_core]).
** Warning: No object file created - nothing loaded **
ok

1> c(foo, ['P']).
** Warning: No object file created - nothing loaded **
ok

1> compile:file(foo, [to_core,binary]).
{ok, foo, {c_module, ...}}

1> {ok, foo, Core} = compile:file(foo, [to_core,binary]).
{ok, foo, {c_module, ...}}
2> io:put_chars(core_pp:format(Core)).
module 'foo' [...]
  ...

> erlc foo.core

1> c(foo, [from_core]).
{ok, foo}

1> {ok, foo, Core} = compile:file(foo, [to_core,binary]).
{ok, foo, {c_module, ...}}
3> {ok, foo, Bin} = compile:forms(Core, [from_core,binary]).
{ok,foo, <<70,79,82,...>>}

4> code:load_binary(foo, "nopath", Bin).
{module,foo}
5> foo:f()
hello
6> code:which(foo).
"nopath"

Failed to generate image: Could not load Ditaa. Either require 'asciidoctor-diagram-ditaamini' or specify the location of the Ditaa JAR(s) using the 'DIAGRAM_DITAA_CLASSPATH' environment variable.
                                                (.erl)                         [] ⇒ Compiler options
                                                   |                           () ⇒ files
                                                   v                           {} ⇒ erlang terms
                                           +---------------+                   boxes ⇒ passes
                                           |    Scanner    |
                                           |   (erl_scan)  |
                                           +---------------+
                                                   |
                                                   v
                                           +---------------+
                                           |  Preprocessor |
                                           |     (epp)     |
                                           +---------------+
                                                   |
                                                   v
                                           +---------------+
                                           |     Parser    |
                                           |  (erl_parse)  |
                                           +---------------+
                                                   |
                                                   v
                                           +---------------+     +---------------+
                                           |     Parse     | --> | user defined  |
                                           |   Transforms  | <-- | transformation|
                                           +---------------+     +---------------+
                                                   |
                                                   +---------> (.Pbeam) [makedep]
                                                   +---------> {dep} [makedep, binary]
                                                   |
                                                   +---------> (.pp) [dpp]
                                                   +---------> {AST} [dpp, binary]
                                                   |
                                                   v
                                           +---------------+
                                           |     Linter    |
                                           |   (erl_lint)  |
                                           +---------------+
                                                   |
                                                   +---------> (.P) ['P']
                                                   +---------> {AST} ['P',binary]
                                                   |
                                                   v
                                           +---------------+
                                           |   Save AST    |
                                           |for debug info |
                                           +---------------+
                                                   |
                                                   v
                                           +---------------+
                                           |Expand Imports |
                                           |  and Records  |
                                           +---------------+
                                                   |
                                                   +---------> (.E) ['E']
                                                   +---------> {.E} ['E', binary]
                                                   |
                                                   v
                                           +---------------+
                                           |     Core      |
                                           |    Erlang     |
                                           +---------------+
                                                   |
                                                   :

Failed to generate image: Could not load Ditaa. Either require 'asciidoctor-diagram-ditaamini' or specify the location of the Ditaa JAR(s) using the 'DIAGRAM_DITAA_CLASSPATH' environment variable.
                                                   :                           [] ⇒ Compiler options
                                                   |                           () ⇒ files
                                           +---------------+                   {} ⇒ erlang terms
                                           |     Core      |                   boxes ⇒ passes
                                           |    Erlang     |
                                           +---------------+
                                                   |
                                                   +---------> (.core) [to_core0]
                                                   +---------> {core} [to_core0,binary]
                                                   |
                                                   v
                     +---------------+     +---------------+     +---------------+
    from_core ---->  |      Core     | ... |      Core     | ... |      Core     |
  erlc *.core ---->  |     Pass 0    |     |     Pass 1    |     |     Pass N    |
                     +---------------+     +---------------+     +---------------+
                                                   |
                                                   +---------> (.core) [to_core]
                                                   +---------> {core} [to_core,binary]
                                                   |
                                                   v
                                           +---------------+
                                           |    Kernel     |
                                           |    Erlang     |
                                           +---------------+
                                                   |
                                                   v
                     +---------------+     +---------------+     +---------------+
                     |    Kernel     | ... |    Kernel     | ... |    Kernel     |
                     |    Pass 0     |     |    Pass 1     |     |    Pass N     |
                     +---------------+     +---------------+     +---------------+
                                                   |
                                                   v
                                           +---------------+
                                           |   BEAM ASM    |
                                           |               |
                                           +---------------+
                                                   |
                                                   v
                     +---------------+     +---------------+     +---------------+
     from_asm ---->  |     ASM       | ... |     ASM       | ... |     ASM       |
     erlc *.S ---->  |    Pass 0     |     |    Pass 1     |     |    Pass N     |
                     +---------------+     +---------------+     +---------------+
                                                   |
                                                   +---------> (.S) ['S']
                                                   +---------> {.S} ['S', binary]
                                                   |
                                                   v
                                           +---------------+
                                           |  BEAM Binary  |
                                           |               |
                                           +---------------+
                                                   |
                                                   v

                                                (.beam)

 1> compile:options().
 dpp - Generate .pp file
 'P' - Generate .P source listing file

 'E' - Generate .E source listing file

 'S' - Generate .S file

-module(world).
-export([hello/0]).

-include("world.hrl").

hello() -> ?GREETING.

-define(GREETING, "hello world").

2> c(world, ['P']).
** Warning: No object file created - nothing loaded **
ok

-file("world.erl", 1).

-module(world).

-export([hello/0]).

-file("world.hrl", 1).

-file("world.erl", 4).

hello() ->
    "hello world".

3> c(world, ['E']).
** Warning: No object file created - nothing loaded **
ok

-vsn("\002").

-file("world.erl", 1).

-file("world.hrl", 1).

-file("world.erl", 5).

hello() ->
    "hello world".

module_info() ->
    erlang:get_module_info(world).

module_info(X) ->
    erlang:get_module_info(world, X).

3> c(world, ['S']).
** Warning: No object file created - nothing loaded **
ok

{module, world}.  %% version = 0

{exports, [{hello,0},{module_info,0},{module_info,1}]}.

{attributes, []}.

{labels, 7}.


{function, hello, 0, 2}.
  {label,1}.
    {line,[{location,"world.erl",6}]}.
    {func_info,{atom,world},{atom,hello},0}.
  {label,2}.
    {move,{literal,"hello world"},{x,0}}.
    return.


{function, module_info, 0, 4}.
  {label,3}.
    {line,[]}.
    {func_info,{atom,world},{atom,module_info},0}.
  {label,4}.
    {move,{atom,world},{x,0}}.
    {line,[]}.
    {call_ext_only,1,{extfunc,erlang,get_module_info,1}}.


{function, module_info, 1, 6}.
  {label,5}.
    {line,[]}.
    {func_info,{atom,world},{atom,module_info},1}.
  {label,6}.
    {move,{x,0},{x,1}}.
    {move,{atom,world},{x,0}}.
    {line,[]}.
    {call_ext_only,2,{extfunc,erlang,get_module_info,2}}.

{ok, BEAM_Code} = file:consult("world.S").

-module(json_test).
-compile({parse_transform, json_parser}).
-export([test/1]).

test(V) ->
    <<{{
      "name"  : "Jack (\"Bee\") Nimble",
      "format": {
                 "type"      : "rect",
                 "widths"     : [1920,1600],
                 "height"    : (-1080),
                 "interlace" : false,
                 "frame rate": V
                }
      }}>>.

-module(json_parser).
-export([parse_transform/2]).

parse_transform(AST, _Options) ->
  io:format("~p~n", [AST]),
  AST.

> c(json_parser).
{ok,json_parser}
2> c(json_test).
[{attribute,1,file,{"./json_test.erl",1}},
 {attribute,1,module,json_test},
 {attribute,3,export,[{test,1}]},
 {function,5,test,1,
  [{clause,5,
    [{var,5,'V'}],
    [],
    [{bin,6,
      [{bin_element,6,
        {tuple,6,
         [{tuple,6,
           [{remote,7,{string,7,"name"},{string,7,"Jack (\"Bee\") Nimble"}},
            {remote,8,
             {string,8,"format"},
             {tuple,8,
              [{remote,9,{string,9,"type"},{string,9,"rect"}},
               {remote,10,
                {string,10,"widths"},
                {cons,10,
                 {integer,10,1920},
                 {cons,10,{integer,10,1600},{nil,10}}}},
               {remote,11,{string,11,"height"},{op,11,'-',{integer,11,1080}}},
               {remote,12,{string,12,"interlace"},{atom,12,false}},
               {remote,13,{string,13,"frame rate"},{var,13,'V'}}]}}]}]},
        default,default}]}]}]},
 {eof,16}]
./json_test.erl:7: illegal expression
./json_test.erl:8: illegal expression
./json_test.erl:5: Warning: variable 'V' is unused
error

-module(json_parser).
-export([parse_transform/2]).

parse_transform(AST, _Options) ->
    json(AST, []).

-define(FUNCTION(Clauses), {function, Label, Name, Arity, Clauses}).

%% We are only interested in code inside functions.
json([?FUNCTION(Clauses) | Elements], Res) ->
    json(Elements, [?FUNCTION(json_clauses(Clauses)) | Res]);
json([Other|Elements], Res) -> json(Elements, [Other | Res]);
json([], Res) -> lists:reverse(Res).

%% We are interested in the code in the body of a function.
json_clauses([{clause, CLine, A1, A2, Code} | Clauses]) ->
    [{clause, CLine, A1, A2, json_code(Code)} | json_clauses(Clauses)];
json_clauses([]) -> [].


-define(JSON(Json), {bin, _, [{bin_element
                                         , _
                                         , {tuple, _, [Json]}
                                         , _
                                         , _}]}).

%% We look for: <<"json">> = Json-Term
json_code([])                     -> [];
json_code([?JSON(Json)|MoreCode]) -> [parse_json(Json) | json_code(MoreCode)];
json_code(Code)                   -> Code.

%% Json Object -> [{}] | [{Label, Term}]
parse_json({tuple,Line,[]})            -> {cons, Line, {tuple, Line, []}};
parse_json({tuple,Line,Fields})        -> parse_json_fields(Fields,Line);
%% Json Array -> List
parse_json({cons, Line, Head, Tail})   -> {cons, Line, parse_json(Head),
                                                       parse_json(Tail)};
parse_json({nil, Line})                -> {nil, Line};
%% Json String -> <<String>>
parse_json({string, Line, String})     -> str_to_bin(String, Line);
%% Json Integer -> Integer
parse_json({integer, Line, Integer})   -> {integer, Line, Integer};
%% Json Float -> Float
parse_json({float, Line, Float})       -> {float, Line, Float};
%% Json Constant -> true | false | null
parse_json({atom, Line, true})         -> {atom, Line, true};
parse_json({atom, Line, false})        -> {atom, Line, false};
parse_json({atom, Line, null})         -> {atom, Line, null};

%% Variables, should contain Erlang encoded Json
parse_json({var, Line, Var})         -> {var, Line, Var};
%% Json Negative Integer or Float
parse_json({op, Line, '-', {Type, _, N}}) when Type =:= integer
                                             ; Type =:= float ->
                                          {Type, Line, -N}.
%% parse_json(Code)                  -> io:format("Code: ~p~n",[Code]), Code.

-define(FIELD(Label, Code), {remote, L, {string, _, Label}, Code}).

parse_json_fields([], L) -> {nil, L};
%% Label : Json-Term  --> [{<<Label>>, Term} | Rest]
parse_json_fields([?FIELD(Label, Code) | Rest], _) ->
    cons(tuple(str_to_bin(Label, L), parse_json(Code), L)
         , parse_json_fields(Rest, L)
         , L).


tuple(E1, E2, Line)    -> {tuple, Line, [E1, E2]}.
cons(Head, Tail, Line) -> {cons, Line, Head, Tail}.

str_to_bin(String, Line) ->
    {bin
     , Line
     , [{bin_element
         , Line
         , {string, Line, String}
         , default
         , default
        }
       ]
    }.

1> c(json_parser).
{ok,json_parser}
2> c(json_test).
{ok,json_test}
3> json_test:test(42).
[{<<"name">>,<<"Jack (\"Bee\") Nimble">>},
{<<"format">>,
  [{<<"type">>,<<"rect">>},
   {<<"widths">>,[1920,1600]},
   {<<"height">>,-1080},
   {<<"interlace">>,false},
   {<<"frame rate">>,42}]}]

Failed to generate image: Could not load Ditaa. Either require 'asciidoctor-diagram-ditaamini' or specify the location of the Ditaa JAR(s) using the 'DIAGRAM_DITAA_CLASSPATH' environment variable.
  +----------------------------+
  |           Process          |
  |                            |
  |  +---------+  +---------+  |
  |  |   PCB   |  |  Stack  |  |
  |  +---------+  +---------+  |
  |                            |
  |  +---------+  +---------+  |
  |  | Mailbox |  |  Heap   |  |
  |  +---------+  +---------+  |
  |                            |
  +----------------------------+

1> erlang:process_display(self(), backtrace).
Program counter: 0x00007fdf9baa2e78 (erlang:self/0 + 32)

0x00007fdedf247480 Return addr 0x00007fdf9baa2118 (erlang:process_display/2 + 128)
y(0)     []
y(1)     backtrace
y(2)     <0.89.0>

0x00007fdedf2474a0 Return addr 0x00007fdf9bbb7644 (erl_eval:do_apply/7 + 308)
y(0)     none
y(1)     []

0x00007fdedf2474b8 Return addr 0x00007fdf9bf0e430 (shell:exprs/7 + 536)
y(0)     []
y(1)     []
y(2)     []
y(3)     []
y(4)     cmd
y(5)     []
y(6)     {value,#Fun<shell.5.46532814>}
y(7)     {eval,#Fun<shell.23.46532814>}
y(8)     #Ref<0.908573933.3456499713.143140>
y(9)     []

0x00007fdedf247510 Return addr 0x00007fdf9bf0dc60 (shell:eval_exprs/7 + 152)
y(0)     []
y(1)     []
y(2)     []
y(3)     []
y(4)     <0.88.0>
y(5)     Catch 0x00007fdf9bf0dd0e (shell:eval_exprs/7 + 326)

0x00007fdedf247548 Return addr 0x00007fdf9bf0d87c (shell:eval_loop/4 + 564)
y(0)     #Ref<0.908573933.3456499713.143140>
y(1)     #Ref<0.908573933.3456499713.143160>
y(2)     <0.88.0>

0x00007fdedf247568 Return addr 0x00007fdf9ba2d1f8 (<terminate process normally>)
true

$ERL_TOP/bin/cerl -debug -rgdb
GNU gdb (Ubuntu 15.0.50.20240403-0ubuntu1) 15.0.50.20240403-git
...
Reading symbols from beam.debug.smp...
%---------------------------------------------------------------------------
% Use etp-help for a command overview and general help.
%
% To use the Erlang support module, the environment variable ROOTDIR
% must be set to the toplevel installation directory of Erlang/OTP,
% so the etp-commands file becomes:
%     $ROOTDIR/erts/etc/unix/etp-commands
% Also, erl and erlc must be in the path.
%---------------------------------------------------------------------------
etp-set-max-depth 20
etp-set-max-string-length 100
--------------- System Information ---------------
OTP release: 24
ERTS version: 12.3.2.17
Arch: x86_64-pc-linux-gnu
Endianness: Little
Word size: 64-bit
BeamAsm support: yes
--Type <RET> for more, q to quit, c to continue without paging--
SMP support: yes
Thread support: yes
Kernel poll: Supported
Debug compiled: yes
Lock checking: yes
Lock counting: no
System not initialized
--------------------------------------------------

(gdb) run
Starting program: /home/happi/hh/theBeamBook/otp24/bin/x86_64-pc-linux-gnu/beam.debug.smp -- -root /home/happi/hh/theBeamBook/otp24 -progname /home/happi/hh/theBeamBook/otp24/bin/cerl -debug -- -home /home/happi -- -emu_type debug

This GDB supports auto-downloading debuginfo from the following URLs:
  <https://debuginfod.ubuntu.com>
Enable debuginfod for this session? (y or [n]) y
Debuginfod has been enabled.
To make this setting permanent, add 'set debuginfod enabled on' to .gdbinit.
warning: could not find '.gnu_debugaltlink' file for /lib/x86_64-linux-gnu/libtinfo.so.6
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[New Thread 0x7fffb6baf6c0 (LWP 2185)]
...
[New Thread 0x7fff9f4fa6c0 (LWP 2232)]
Erlang/OTP 24 [erts-12.3.2.17] [source] [64-bit] [smp:16:16] [ds:16:16:10] [async-threads:1] [jit] [type-assertions] [debug-compiled] [lock-checking]

Eshell V12.3.2.17  (abort with ^G)
1>

-module(mini_proc).
-export([wait/0]).

wait() ->
  X = {timestamp, erlang:timestamp()},
  receive _ -> X end,
  X.

1> c(mini_proc).
{ok,mini_proc}
9> P3 = spawn(mini_proc, wait, []).
<0.101.0>

    Thread 1 "beam.debug.smp" received signal SIGINT, Interrupt.
                                                                [Switching to Thread 0x7ffff79b3c40 (LWP 2170)]
(gdb)

(gdb) thread 7
[Switching to thread 7 (Thread 0x7fffb40b96c0 (LWP 2191))]
(gdb) etp-processes
---
  Pix: 0
  Pid: <0.0.0>
  State: prq-prio-normal | usr-prio-normal | act-prio-normal

  Flags: trap-exit
  Registered name: init
  Current function: unknown
  I: #Cp<init:loop/1+0x64>
  Heap size: 987
  Old-heap size: 987
  Mbuf size: 38
  Msgq len: 0 (inner=0, outer=0)
  Msgq Flags: on-heap
  Parent: []
  Pointer: (Process*)0x5555561301c8

...

---
  Pix: 808
  Pid: <0.101.0>
  State: prq-prio-normal | usr-prio-normal | act-prio-normal

  Flags:
  Current function: unknown
  I: #Cp<0x7fffb53711dc>
  Heap size: 233
  Old-heap size: 0
  Mbuf size: 0
  Msgq len: 0 (inner=0, outer=0)
  Msgq Flags: on-heap
  Parent: <0.93.0>
  Pointer: (Process*)0x7fff9ed6e030
---
  Pix: 816
  Pid: <0.102.0>
  State: prq-prio-normal | usr-prio-normal | act-prio-normal

  Flags:
  Current function: unknown
  I: #Cp<io:execute_request/3+0x1a4>
  Heap size: 233
  Old-heap size: 0
  Mbuf size: 0
  Msgq len: 0 (inner=0, outer=0)
  Msgq Flags: on-heap
  Parent: <0.79.0>
  Pointer: (Process*)0x7fff9ed6dce8
---
(gdb)

(gdb) set $p = ((Process *) 0x7fff9ed6e030)
(gdb) etp-stackdump $p
% Stacktrace (3)
I: #Cp<0x7fffb53711dc>.
0: {timestamp,{1747,147859,212377}}.
1: #Cp<0x7fffb4c14a78>.
2: #Cp<0x7fffb4c14a78>.
(gdb) etp-heapdump $p
% heapdump (7):
 0x7fff9eaf8278: | H:   3-tuple | I:      1747 | I:    147859 | I:    212377 | H:   2-tuple |    timestamp | B:0x9eaf827a
(gdb)

print *((Process *) 0x7fff9ed6e030)
$2 = {common =
      {id = 3470333576787,
       refc = {atmc = {counter = 1}, sint = 1},
       tracer = 59, trace_flags = 167772160,
       timer = {counter = 0},
       u = {alive = {started_interval = 263, reg = 0x0, links = 0x0,
                    lt_monitors = 0x0, monitors = 0x0},
                   release = {later = 263, func = 0x0, data = 0x0, next = 0x0}}},
      htop = 0x7fff9eaf82b0,
      stop = 0x7fff9eaf89a8,
      fcalls = 3998,
      freason = 0,
      fvalue = 59,
      heap = 0x7fff9eaf8278,
      hend = 0x7fff9eaf89c0,
      abandoned_heap = 0x0,
      heap_sz = 233,
      min_heap_size = 233,
      min_vheap_size = 46422,
      max_heap_size = 3,
      arity = 0,
      arg_reg = 0x7fff9ed6e0f8,
      max_arg_reg = 6,
      def_arg_reg = {588235, 322955, 59, 14178673876263027908, 14178673876263027908, 4000},
      i = 0x7fffb53711dc <mini_proc:wait/0+140>,
      catches = 0, rcount = 0, schedule_count = 0,
      reds = 6, flags = 0, group_leader = 2267742733347, ftrace = 59, next = 0x555556142888,
      uniq = 0,
      sig_qs = {first = 0x0, last = 0x7fff9ed6e170, save = 0x7fff9ed6e170, cont = 0x0,
                cont_last = 0x7fff9ed6e188,
                nmsigs = {next = 0x0, last = 0x0},
                recv_mrk_blk = 0x0, len = 0, flags = 2},
      bif_timers = 0x0, dictionary = 0x0,
      seq_trace_clock = 0, seq_trace_lastcnt = 0, seq_trace_token = 59,
      u = {real_proc = 0x8f9cb, terminate = 0x8f9cb,
           initial = {module = 588235, function = 322955, arity = 0}},
      current = 0x0, parent = 3195455669715, static_flags = 0,
      high_water = 0x7fff9eaf8278,
      old_hend = 0x0,
      old_htop = 0x0,
      old_heap = 0x0,
      gen_gcs = 0,
      max_gen_gcs = 65535,
      off_heap = {first = 0x0, overhead = 0},
      mbuf = 0x0, live_hf_end = 0xfffffffffffffff8, msg_frag = 0x0, mbuf_sz = 0,
      psd = {counter = 0},
      bin_vheap_sz = 46422, bin_old_vheap_sz = 46422, bin_old_vheap = 0,
      sys_task_qs = 0x0, dirty_sys_tasks = 0x0,
      state = {counter = 42}, dirty_state = {counter = 0},
      sig_inq = {first = 0x0, last = 0x7fff9ed6e2a8, len = 0,
                 nmsigs = {next = 0x0, last = 0x0}},
      trace_msg_q = 0x0,lock = {flags = {counter = 0},
                                queue = {0x0, 0x0, 0x0, 0x0, 0x0},
                                locked = {{counter = 0}, {counter = 0}, {counter = 0},
                                          {counter = 0}, {counter = 0}}},
      scheduler_data = 0x0, run_queue = {counter = 140736249294720},
      last_htop = 0x7fff9eaf8298, last_mbuf = 0x0, heap_hfrag = 0x0, last_old_htop = 0x0,
      debug_reds_in = 4000
     }

4> show:tag_to_type(3470333576787).
pid
5>

Failed to generate image: Could not load Ditaa. Either require 'asciidoctor-diagram-ditaamini' or specify the location of the Ditaa JAR(s) using the 'DIAGRAM_DITAA_CLASSPATH' environment variable.
  hend ->  +----+    -
           |    |    ^
           |    |    |             -
  htop ->  |    |    | heap_sz*8   ^
           |....|    | hend-heap   | min_heap_size
           |....|    v             v
  heap ->  +----+    -             -
          The Heap

Failed to generate image: Could not load Ditaa. Either require 'asciidoctor-diagram-ditaamini' or specify the location of the Ditaa JAR(s) using the 'DIAGRAM_DITAA_CLASSPATH' environment variable.
  +----------------------------+
  |           Process          |
  |                            |
  |  +---------+  +---------+  |
  |  |   PCB   |  |  Stack  |  |
  |  +---------+  +---------+  |
  |               |  free   |  |
  |  +---------+  +---------+  |
  |  | Mailbox |  |  Heap   |  |
  |  +---------+  +---------+  |
  |                            |
  +----------------------------+

Failed to generate image: Could not load Ditaa. Either require 'asciidoctor-diagram-ditaamini' or specify the location of the Ditaa JAR(s) using the 'DIAGRAM_DITAA_CLASSPATH' environment variable.
  hend ->  +----+    -
           |....|    ^
  stop ->  |    |    |
           |    |    |
           |    |    |             -
  htop ->  |    |    | heap_sz     ^
           |....|    |             | min_heap_size
           |....|    v             v
  heap ->  +----+    -             -
          The Heap

    Eterm *high_water;
    Eterm *old_hend;     /* Heap pointers for generational GC. */
    Eterm *old_htop;
    Eterm *old_heap;
    Uint max_heap_size;  /* Maximum size of heap (in words). */
    Uint16 gen_gcs;      /* Number of (minor) generational GCs. */
    Uint16 max_gen_gcs;	 /* Max minor gen GCs before fullsweep. */

Failed to generate image: Could not load Ditaa. Either require 'asciidoctor-diagram-ditaamini' or specify the location of the Ditaa JAR(s) using the 'DIAGRAM_DITAA_CLASSPATH' environment variable.
  +---------+                +-------+
  |  PCB    |                | Stack |  +-------+ <- old_hend
  +---------+                +-------+  +       +
                             | free  |  +-------+ <- old_htop
  +---------+  high_water -> +-------+  |  Old  |
  | Mailbox |                | Heap  |  | Heap  |
  +---------+                +-------+  +-------+ <- old_heap

Failed to generate image: Could not load Ditaa. Either require 'asciidoctor-diagram-ditaamini' or specify the location of the Ditaa JAR(s) using the 'DIAGRAM_DITAA_CLASSPATH' environment variable.
 +-------+             +-------+  +-------+
 |  PCB  |             | Stack |  |  PD   |
 +-------+             +-------+  +-------+
                       | free  |
 +-------+  +-------+  +-------+  +-------+
 | M-box |  | M-box |  | Heap  |  |  Old  |
 | intern|  | inq   |  |       |  | Heap  |
 +-------+  +-------+  +-------+  +-------+

 +-------+  +-------+  +-------+  +-------+
 | m−buf |  | m−buf |  | m−buf |  | m−buf |
 +-------+  +-------+  +-------+  +-------+

1> Ps = erlang:processes().
[<0.0.0>,<0.3.0>,<0.6.0>,<0.7.0>,<0.9.0>,<0.10.0>,<0.11.0>,
 <0.12.0>,<0.13.0>,<0.14.0>,<0.15.0>,<0.16.0>,<0.17.0>,
 <0.19.0>,<0.20.0>,<0.21.0>,<0.22.0>,<0.23.0>,<0.24.0>,
 <0.25.0>,<0.26.0>,<0.27.0>,<0.28.0>,<0.29.0>,<0.33.0>]
2> P = self().
<0.33.0>
3> erlang:process_info(P).
[{current_function,{erl_eval,do_apply,6}},
 {initial_call,{erlang,apply,2}},
 {status,running},
 {message_queue_len,0},
 {messages,[]},
 {links,[<0.27.0>]},
 {dictionary,[]},
 {trap_exit,false},
 {error_handler,error_handler},
 {priority,normal},
 {group_leader,<0.26.0>},
 {total_heap_size,17730},
 {heap_size,6772},
 {stack_size,24},
 {reductions,25944},
 {garbage_collection,[{min_bin_vheap_size,46422},
                      {min_heap_size,233},
                      {fullsweep_after,65535},
                      {minor_gcs,1}]},
 {suspending,[]}]
 4>  lists:keysort(2,[{P,element(2,erlang:process_info(P,
     total_heap_size))} || P <- Ps]).
[{<0.10.0>,233},
 {<0.13.0>,233},
 {<0.14.0>,233},
 {<0.15.0>,233},
 {<0.16.0>,233},
 {<0.17.0>,233},
 {<0.19.0>,233},
 {<0.20.0>,233},
 {<0.21.0>,233},
 {<0.22.0>,233},
 {<0.23.0>,233},
 {<0.25.0>,233},
 {<0.28.0>,233},
 {<0.29.0>,233},
 {<0.6.0>,752},
 {<0.9.0>,752},
 {<0.11.0>,1363},
 {<0.7.0>,1597},
 {<0.0.0>,1974},
 {<0.24.0>,2585},
 {<0.26.0>,6771},
 {<0.12.0>,13544},
 {<0.33.0>,13544},
 {<0.3.0>,15143},
 {<0.27.0>,32875}]
9>

Failed to generate image: Could not find the 'dot' executable in PATH; add it to the PATH or specify its location using the 'graphvizdot' document attribute

digraph G {
  overlap=false;
  splines=false;
  node[fontname=Helvetica fontsize=22];
  edge [penwidth=0.5]

  any[shape=plaintext, label="any()"];
  number[shape=plaintext, label="number()"];
  atom[shape=plaintext, label="atom()"];
  reference[shape=plaintext, label="reference()"];
  fun[shape=plaintext, label="fun()"];
  port[shape=plaintext, label="port()"];
  pid[shape=plaintext, label="pid()"];
  tuple[shape=plaintext, label="tuple()"];
  map[shape=plaintext, label="map()"];
  list[shape=plaintext, label="list()"];
  binary[shape=plaintext, label="binary()"];
  integer[shape=plaintext, label="integer()"];
  float[shape=plaintext, label="float()"];
  nil[shape=plaintext, label="nil()"];
  cons[shape=plaintext, label="cons()"];
  boolean[shape=plaintext, label="boolean()"];
  false[shape=plaintext, label="false()"];
  true[shape=plaintext, label="true()"];
  dummy0[shape=point, width=0.004];
  dummy1[shape=point, width=0.004];
  dummy2[shape=point, width=0.004];
  none[shape=plaintext, label="none()"];
  gt0[shape=plaintext, label="<" fontcolor=gray];
  gt1[shape=plaintext, label="<" fontcolor=gray];
  gt2[shape=plaintext, label="<" fontcolor=gray];
  gt3[shape=plaintext, label="<" fontcolor=gray];
  gt4[shape=plaintext, label="<" fontcolor=gray];
  gt5[shape=plaintext, label="<" fontcolor=gray];
  gt6[shape=plaintext, label="<" fontcolor=gray];
  gt7[shape=plaintext, label="<" fontcolor=gray];
  gt8[shape=plaintext, label="<" fontcolor=gray];
  gt9[shape=plaintext, label="<" fontcolor=gray];

  subgraph cluster_1 {
    style=invis
    {rank=same gt0 gt1 gt2 gt3 gt4 gt5 gt6 gt7 gt8 number, atom, reference, fun, port, pid, tuple, map, list, binary}
    number -> gt0 -> atom -> gt1 -> reference -> gt2 -> fun -> gt3 -> port -> gt4 -> pid -> gt5 -> tuple -> gt6 -> map -> gt7 -> list -> gt8 -> binary
    [color=transparent arrowhead=none labelcolor=gray];
  }

  subgraph cluster_2 {
    style=invis
    {rank=same gt9 true, false}
    dummy1 dummy2 false -> gt9 -> true
    [color=transparent arrowhead=none labelcolor=gray];
  }

  {rank=same integer, float, boolean, nil, cons, dummy0}
  any->number[dir=none];
  number->integer[dir=none];
  number->float[dir=none];
  any->atom[dir=none];
  atom->boolean[dir=none];
  any->reference[dir=none];
  any->fun[dir=none];
  any->port[dir=none];
  any->pid[dir=none];
  any->tuple[dir=none];
  any->map[dir=none];
  any->list[dir=none];
  list->nil[dir=none];
  list->cons[dir=none];
  any->binary[dir=none];
  binary->dummy0[dir=none];
  integer->dummy1[dir=none];
  dummy1->none[dir=none];
  float->dummy2[dir=none];
  dummy2->none[dir=none];
  atom->none[dir=none];
  boolean->false[dir=none];
  boolean->true[dir=none];
  boolean->none[dir=none];
  false->none[dir=none];
  true->none[dir=none];
  reference->none[dir=none];
  fun->none[dir=none];
  port->none[dir=none];
  pid->none[dir=none];
  tuple->none[dir=none];
  map->none[dir=none];
  nil->none[dir=none];
  cons->none[dir=none];
  dummy0->none[dir=none];

}

struct cons_cell {
    Eterm *head;     /* the value */
    Eterm *tail;     /* the next element */
};

Eshell V15.2.2 (press Ctrl+G to abort, type help(). for help)
1> [88,89,90].
"XYZ"

2> [955, 960, 963].
[955,960,963]

$ erl +pc unicode
Erlang/OTP 27 [erts-15.2.2] [source] [64-bit] [smp:8:8] [ds:8:8:10] [async-threads:1] [jit:ns]

Eshell V15.2.2 (press Ctrl+G to abort, type help(). for help)
1> [955, 960, 963].
"λπσ"

Failed to generate image: Could not load Ditaa. Either require 'asciidoctor-diagram-ditaamini' or specify the location of the Ditaa JAR(s) using the 'DIAGRAM_DITAA_CLASSPATH' environment variable.

 hend ->     +-------- -------- -------- --------+
             |              ...                  |
             |              ...                  |
             |00000000 00000000 00000000 10000001| 128 + list tag  -----------------+
 stop ->     |                                   |                                  |
                                                                                    |
 htop ->     |                                   |                                  |
         132 |00000000 00000000 00000000 01111001| 120 + list tag  -----------------|--+
         128 |00000000 00000000 00000110 10001111| (h) 104 bsl 4 + small int tag <--+  |
         124 |00000000 00000000 00000000 01110001| 112 + list tag  --------------------|--+
         120 |00000000 00000000 00000110 01011111| (e) 101 bsl 4 + small int tag <-----+  |
         116 |00000000 00000000 00000000 01101000| 104 + list tag  -----------------------|--+
         112 |00000000 00000000 00000110 11001111| (l) 108 bsl 4 + small int tag <--------+  |
         108 |00000000 00000000 00000000 01110001| 96 + list tag  ---------------------------|--+
         104 |00000000 00000000 00000110 11001111| (l) 108 bsl 4 + small int tag <-----------+  |
         100 |11111111 11111111 11111111 11111011| NIL                                          |
          96 |00000000 00000000 00000110 11111111| (o) 111 bsl 4 + small int tag <--------------+
             |                ...                |
 heap ->     +-----------------------------------+

 aaaaaaaa...aaaaaaaaaaaaaaaa tttt 00

 0000 00  ARITYVAL (Tuples)
 0001 00  BINARY_AGGREGATE                |
 001s 00  BIGNUM with sign bit            |
 0100 00  REF                             |
 0101 00  FUN                             | THINGS
 0110 00  FLONUM                          |
 0111 00  EXPORT                          |
 1000 00  REFC_BINARY     |               |
 1001 00  HEAP_BINARY     | BINARIES      |
 1010 00  SUB_BINARY      |               |
 1011 00    [UNUSED]
 1100 00  EXTERNAL_PID  |                 |
 1101 00  EXTERNAL_PORT | EXTERNAL THINGS |
 1110 00  EXTERNAL_REF  |                 |
 1111 00  MAP

push 8
push 17
push 2
multiply
add

compile(String) ->
    [ParseTree] = element(2,
			  erl_parse:parse_exprs(
			    element(2,
				    erl_scan:string(String)))),
    generate_code(ParseTree).

generate_code({op, _Line, '+', Arg1, Arg2}) ->
    generate_code(Arg1) ++ generate_code(Arg2) ++ [add];
generate_code({op, _Line, '*', Arg1, Arg2}) ->
    generate_code(Arg1) ++ generate_code(Arg2) ++ [multiply];
generate_code({integer, _Line, I}) -> [push, I].

interpret(Code) -> interpret(Code, []).

interpret([push, I |Rest], Stack)              -> interpret(Rest, [I|Stack]);
interpret([add     |Rest], [Arg2, Arg1|Stack]) -> interpret(Rest, [Arg1+Arg2|Stack]);
interpret([multiply|Rest], [Arg2, Arg1|Stack]) -> interpret(Rest, [Arg1*Arg2|Stack]);
interpret([],              [Res|_])            -> Res.

1> stack_machine:interpret(stack_machine:compile("8 + 17 * 2.")).
42

BEAMHeader = <<
  IffHeader:4/unit:8 = "FOR1",
  Size:32/big,                  // big endian, how many more bytes are there
  FormType:4/unit:8 = "BEAM"
>>

BEAMChunk = <<
  ChunkName:4/unit:8,           // "Code", "Atom", "StrT", "LitT", ...
  ChunkSize:32/big,
  ChunkData:ChunkSize/unit:8,   // data format is defined by ChunkName
  Padding4:0..3/unit:8
>>

-module(beamfile1).
-export([read/1]).

read(Filename) ->
   {ok, File} = file:read_file(Filename),
   <<"FOR1",
     Size:32/integer,
     "BEAM",
     Chunks/binary>> = File,
   {Size, read_chunks(Chunks, [])}.

read_chunks(<<N,A,M,E, Size:32/integer, Tail/binary>>, Acc) ->
   %% Align each chunk on even 4 bytes
   ChunkLength = align_by_four(Size),
   <<Chunk:ChunkLength/binary, Rest/binary>> = Tail,
   read_chunks(Rest, [{[N,A,M,E], Size, Chunk}|Acc]);
read_chunks(<<>>, Acc) -> lists:reverse(Acc).

align_by_four(N) -> (4 * ((N+3) div 4)).

> beamfile1:read("beamfile1.beam").
{1116, [{"AtU8",127,
 <<0,0,0,16,9,98,101,97,109,102,105,108,101,49,4,114,101,
 97,100,4,102,105,108,...>>}, {"Code",362,
 <<0,0,0,16,0,0,0,0,0,0,0,178,0,0,0,16,0,0,0,5,1,16,...>>},
 {"StrT",8,<<"FOR1BEAM">>},
 {"ImpT",88,<<0,0,0,7,0,0,0,3,0,0,0,4,0,0,0,1,0,0,0,8,...>>},
 {"ExpT",40,<<0,0,0,3,0,0,0,15,0,0,0,1,0,0,0,15,0,0,0,...>>}, {"Meta",29,
 <<131,108,0,0,0,1,104,2,100,0,16,101,110,97,98,108,101, 100,...>>},
 {"LocT",28,<<0,0,0,2,0,0,0,10,0,0,0,1,0,0,0,11,0,...>>}, {"Attr",40,
 <<131,108,0,0,0,1,104,2,100,0,3,118,115,110,108,0,...>>}, {"CInf",122,
 <<131,108,0,0,0,3,104,2,100,0,7,118,101,114,115,...>>}, {"Dbgi",49,
 <<131,104,3,100,0,13,100,101,98,117,103,95,105,110,...>>},
 {"Line",31,<<0,0,0,0,0,0,0,0,0,0,0,12,0,...>>},
 {"Type",80,<<0,0,0,1,0,0,0,4,31,255,0,0,...>>}]}