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GNU poke 2.0 released

From: Jose E. Marchesi
Subject: GNU poke 2.0 released
Date: Thu, 27 Jan 2022 22:01:09 +0100
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/28.0.50 (gnu/linux)

I am happy to announce a new major release of GNU poke, version 2.0.

This release is the result of a year of development.  A lot of things
have changed and improved with respect to the 1.x series; we have
fixed many bugs and added quite a lot of new exciting and useful
features.  See below for a description of many of them.

We have had lots of fun and learned quite a lot in the process; we
really wish you will have at least half of that fun using this tool!

The tarball poke-2.0.tar.gz is now available at

  GNU poke ( is an interactive, extensible
  editor for binary data.  Not limited to editing basic entities such
  as bits and bytes, it provides a full-fledged procedural,
  interactive programming language designed to describe data
  structures and to operate on them.

Thanks to the people who contributed with code and/or documentation to
this release.  In certain but no significant order they are:

   Mohammad-Reza Nabipoor
   Luca Saiu
   Bruno Haible
   Egeyar Bagcioglu
   David Faust
   Guillermo E. Martinez
   Konstantinos Chasialis
   Matt Ihlenfield
   Thomas WeiƟschuh
   Sergei Trofimovich
   Fangrui Song
   Indu Bhagat
   Jordan Yelloz
   Morten Linderud
   Sergio Durigan Junior

As always, thank you all!

User interface updates

  - Types can now be redefined at the prompt.  This allowed us to
    change `load' to always load the requested file/module.

  - The poke command now accepts two additional command-line options in
    order to select which default style to use: --style-dark and
    --style-bright.  The first, which is the default, works good with
    dark backgrounds.  The second works good with bright backgrounds.

  - Invoking the .set command with no arguments now lists all the global
    settings along with their values.  It also emits buttons (terminal
    hyperlinks) to easily toggle boolean settings.

  - The .file dot-command now supports a /c flag, that tells poke it
    must create an empty file with the specified name if it doesn't
    already exist.

  - The :size argument of the dump command is now rounded up to the next
    byte, not truncated down to the previous byte.

  - A new "sub" IO space has been implemented in poke.  It allows to
    create IO spaces that are like narrowed versions of some other IO
    space.  These "sub" IO spaces are created using the new dot-command

    | (poke) .mem scratch
    | (poke) .info ios
    |   Id   Type     Mode   Bias           Size           Name        
    | * #0   MEMORY   rw     0x00000000#B   0x00001000#B   *scratch*
    | (poke) .sub #0, 2, 16, lala
    | (poke) .info ios
    |   Id   Type     Mode   Bias           Size           Name                 
    | * #1   SUB      rw     0x00000002#B   0x00000010#B   sub://0/0x0/0x10/lala
    |   #0   MEMORY   rw     0x00000000#B   0x00001000#B   *scratch*

    At this point accessing the IO space #1 at offset 0#B will modify
    the data in the *scratch* IO space at offset 2#B.

  - GNU poke can now poke at the memory of a running process using the
    new process IOS.  This can be done using the new dot-command .proc:

    | (poke) .proc 30244
    | (poke) .info ios
    |   Id   Type   Mode   Bias           Size                   Name          
    | * #0   PROC   rw     0x00000000#B   0xffffffffffffffff#B   pid://30244

    The command above has opened a new IO space (with id #0) to poke at
    the memory of the running process with PID 30244.

    A flag /m can be passed to .proc to indicate we want poke to create
    additional sub-spaces providing access to the mapped VM ranges of
    the process:

    | (poke) .proc/m 30244
    | (poke) .info ios
    |   Id   Type   Mode   Bias           Size          Name                    
    |   #9   SUB    r      0x00000000#B   0x00001000#B  
    |   #8   SUB    r      0x00000000#B   0x00002000#B  
    |   #7   SUB    r      0x00000000#B   0x00002000#B  
    |   #6   SUB    rw     0x00000000#B   0x00021000#B  
    |   [...]
    | * #0   PROC   rw     0x00000000#B   0xffffffffffffffff#B pid://30244

    See below for the new handler syntax in open to open process IO
    spaces from Poke programs.  Note that the support for process IO
    space is only implemented in GNU/Linux systems.

  - The dump command now shows ?? marks to denote bytes that are not
    readable, for whatever reason.  This happens for example when we try
    to access some non-mapped area of the VM space of a process:

    | (poke) .proc/m 30244
    | (poke) dump :from 0#B :size 16#B
    | 76543210  0011 2233 4455 6677 8899 aabb ccdd eeff  0123456789ABCDEF
    | 00000000: ???? ???? ???? ???? ???? ???? ???? ????  ................

  - The dump command now emits hyperlinks for the shown bytes, if
    requested.  Clicking on them will insert the offset where the byte
    resides in the poke prompt.

  - The dump command now remembers the last used offset per IO space.
    In poke 1.x it just remembered the last globally used offset, which
    was very confusing.

  - The .info ios dot-command now emits [close] buttons if hyperlinks
    are enabled.  Clicking on them closes the referred IO space.

  - The .info ios dot-command now shows the value of the "bias" for each
    open IO space.  See below for more information on this bias.

  - E_constraint exceptions raised when mapping now include some useful
    location information:

    | (poke) Elf64_Ehdr @ 1#B
    | unhandled constraint violation exception
    | constraint expression failed for field Elf_Ident.ei_mag

  - The .info types, .info variables and .info functions dot-commands
    now accept an optional regular expression.  Example:

    | (poke) load elf
    | (poke) .info types Elf64_
    | Name                 Declared at
    | Elf64_Ehdr 
    | Elf64_Off  
    | Elf64_SectionFlags
    | Elf64_Shdr 
    | Elf64_RelInfo
    | [...]

    When listing types, the names in the first column are emitted with a
    nice terminal hyperlink.  Clicking on them will result in executing
    .info type NAME.

  - New dot-command .info type NAME, that prints out a nice and
    informative description of the type with the given name.  Example:

    | (poke) .info type Elf64_File
    | Class:      struct
    | Name:       "Elf64_File"
    | Complete:   no
    | Fields:
    |   ehdr
    |   shdr
    |   phdr
    | Methods:
    |  get_section_name
    |  get_symbol_name
    |  get_sections_by_name
    |  get_sections_by_type
    |  section_name_p
    |  get_string
    |  get_group_signature
    |  get_group_signatures
    |  get_section_group

Poke Language updates

  - Integral structs are struct values that are stored like integers.
    This is a simple real-life example:

    | type Elf_Sym_Info =
    |   struct uint<8>
    |   {
    |     uint<4> st_bind;
    |     uint<4> st_type;
    |   };

    These structs can be used pretty much like regular structs,
    accessing their fields normally.  In poke 1.x it was already
    possible to "integrate" them, i.e. operating with their "integer"
    value by using either an explicit cast:

    | (poke) Elf_Sym_Info { st_bind = 1 } as uint<8>
    | 0x10UB

    or automatically, using them in a context where an integral value is

    | (poke) Elf_Sym_Info { st_bind = 1} + 1
    | 0x11UB

    We are now introducing support for the inverse operation: to
    "deintegrate" an integer into an integral struct value.  This is
    performed by a cast:

    | (poke) 0x10 as Elf_Sym_Info
    | Elf_Sym_Info { st_bind=0x1UB, st_type=0x0UB }

  - Arrays whose elements are integral (integers, other integral arrays,
    or integral structs) can now be also "integrated" and "deintegrated"
    using casts:

    | (poke) [1UB, 0UB] as int
    | 0x10
    | (poke) 0x10 as uint<8>[2]
    | [1UB,0UB]
    | (poke) [[1UB,2UB],[3UB,4UB]] as int
    | 0x1234
    | (poke) 0x1234 as uint<8>[2][2]
    | [[1UB,2UB],[3UB,4UB]]

    This nice feature has been contributed by Mohammad Reza-Nabipoor.

  - Poke programs can now sleep for a number of seconds and nanoseconds
    using the new built-in function sleep.  It has the following

    | fun sleep = (int<64> sec, int<64> nsec = 0) void:

    The sleep is not active, i.e. poke will not consume CPU while it is

  - The only way in poke 1.x to print styled text to the terminal was to
    use the very ugly and clumsy %<..> tags in printf statements.
    This was annoying to use, especially because you were required to
    end every styling class you open in the same statement.  So we added
    a couple of new built-in functions term_begin_class and
    term_end_class.  They are used like this:

    | term_begin_class ("error");
    | print "error: the quux is foobared";
    | term_end_class ("error");

    The functions will raise an exception in case you nest your classes
    the wrong way.

  - It is now possible to emit terminal hyperlinks from Poke programs.
    See "Terminal hyperlinks updates" below for more information on

  - The equality `==' and inequality `!=' operators now work on function
    values.  Two given function values are equal if they are the same
    function value. i.e. given these definitions:

    | fun foo = void: {}
    | fun bar = void: {}

    In this example foo is equal to foo, but foo is not equal to bar
    even if both functions happen to have identical type signature and

  - Now it is a compile-time error to cast any values to function types.
    We plan to support this at some point, since it is needed for things
    like having any fields in structs, but at the moment closure values
    are not tagged with their type at run-time and it is better for the
    user to get compile-time errors.

  - In this release we have changed both the semantics and syntax of
    struct type field initializers.  This change has been motivated by
    our own practical usage of poke.  In poke 1.x a struct field
    initializer had the form:

    | type Foo =
    |   struct
    |   {
    |     int i = 10;
    |     long l;
    |   };

    The initialization of i had two effects: newly constructed Foo
    struct values would have i initialized to 10, and a constraint that
    i must equal 10 was also implied when mapping structs of type Foo.
    This worked well, but we realized it is good to decouple the
    implicit constraint from the initialization value: sometimes you
    need one of these, but not both.  It was also not possible to add
    additional constraints.  So we changed the semantics of the
    construction above to denote "initialize to 10, but no implicit
    constraint", with maybe an additional constraint like in:

    | type Foo =
    |   struct
    |   {
    |     int i = 10 : i < 100;
    |     long l;
    |   };

    And then we added the new syntax:

    | type Foo =
    |   struct
    |   {
    |     int i == 10;
    |     long l;
    |   };

    to denote "initialize to 10, plus implicit constraint i == 10."

  - The Poke language is quite exception-oriented.  A good example of
    this is the way to detect whether a given alternative in an union is
    the currently selected one: refer to it and see if an E_elem
    exception gets raised.  This in practice leads to code like this:

    | try { length.indefinite; return 1; }
    | catch if E_elem { return 0; }

    This is so common that we have introduced a new "exception
    conditional" operator ?!.  The above code can now be rewritten as:

    | return length.indefinite ?! E_elem;

    The new operator also has a { ... } ?! EXCEPTION form where the code
    to execute is a compound statement.

  - Constraints in struct type fields are very often related to the
    values of other fields in the same struct.  The relationship is
    often in the form "if field X has value N, then I should have a
    value M".  We have added a new "logical implication" operator =>
    (inspired from the recutils operator with the same name) that
    implements this logic:

    | A => B :=: !A || (A && B)

    For example:

    | uint<1> encoding;
    | uint<5> tag_number : tag_number == BER_TAG_REAL => encoding == 1;

    Meaning that if tag_number denotes a "real" then encoding must be 1.
    If tag_number does not denote a "real" then the value of encoding is

  - Mohammad-Reza Nabipoor has contributed support for a new built-in
    function format, that is able to format a string out of a format
    string and a list of values.  For example:

    | var s = format ("%s - %s (%i32d)", name, sex, age);

    Will format a string in s like:

    | "Francisco Maganto - male (63)"

    The format string is identical to the one used by printf, and
    therefore it also accepts %v tags to format nested complex values
    like arrays and structs.

  - Exception structs have been expanded to include two additional
    fields: location and msg.  Both new fields are strings, and are used
    to convey location information (like the field whose constraint
    expression failed resulting in an E_constraint) and an explanation
    of why the exception was raised, respectively.  There is no more
    need to abuse the field name for these purposes.

  - Much like in C, the Poke printf format strings use % to introduce
    formatting tags, like %i32d.  In poke 1.x it was embarrassingly not
    possible to denote the character % itself.  Now %% can be used in
    printf format strings in order to denote a single % character.

  - If a struct type has labels and all of them are constant, it is now
    considered a complete type. i.e. a type whose size is known at
    compile-time.  This makes it possible to use it in sizeof or as the
    unit of an offset.

  - The Poke Virtual Machine settings that configure output are now
    accessible programmatically from Poke using a set of new built-ins:

    | vm_{obase,opprint,oacutoff,odepth,oindent,omaps,omode}
    | vm_set_{obase,opprint,oacutoff,odepth,oindent,omaps,omode}

  - We added introspection capabilities: typeof. XXX.

Standard Poke Library updates

  - The atoi standard function has been improved in order to parse
    integers with signs.

  - The ltos standard function now works for any numeration base from 1
    to 16, included.

  - New standard functions opensub and openproc have been introduced to
    help with the creation of "sub" and process IO spaces, respectively.
    See below under "IO subsystem updates" for more information.

  - A new standard function exit has been added to the standard library,
    that provides a familiar way to exit a Poke program with an optional
    exit code:

    | fun exit = (int<32> exit_code 0)

    This is just a wrapper to the more "pokeish" and less conventional
    way of exiting, which is to raise an exception of type EC_exit:

    | raise Exception { code = EC_exit, exit_status = exit_code };

  - In poke 1.x we forgot to emit an error at compile-time when the user
    defined an union type as pinned.  This obviously doesn't make any
    sense (all the alternatives of an union are "pinned") so now a
    compile-time error is raised.

  - We have realized that it doesn't make much sense for pinned struct
    types (whose fields all have an implicit offset of zero bytes) to
    have field labels.  To avoid confusing the user, the compiler now
    emits a compile-time error if such a type is defined.

  - Unions can no longer have alternatives with labels.  This worked in
    poke 1.x, but had complicated semantics with little real practical
    benefit.  So now a compile-time error is raised if such a type is

IO subsystem updates

  - Each open IO space now maintains a "bias", which is a bit-offset.
    This bias is added to the offset specified in every read or write
    access to the IO space.  This bias is programmable, and can be read
    and set by Poke programs using two new built-in calls:

    | fun iobias = (int<32> ios = get_ios)
    | fun iosetbias = (offset<uint<64,b> bias = 0#b, int<32> ios = get_ios)

    Note how the positioning and default values of these functions makes
    it comfortable to use them at the (poke) prompt.

  - Poke programs can now poke at the standard input, standard output
    and standard error output of the running poke process using the new
    stream IO spaces.

    The new available handlers (to be used with open) are <stdin>,
    <stdout> and <stderr>.  A good application of these IO
    spaces is to write filter utilities in Poke.

    This support has been contributed by Egeyar Bagcioglu.

  - The IOS_F_* flags used in the open builtin has been rationalized.
    As a consequence the IOS_F_TRUNCATE flag has been removed.

  - There is a new built-in ioflags that returns the flags used to open
    some particular IO space.

  - open now raises an E_perm exception if the user doesn't have enough
    credentials when opening an IO space.  This can happen for example
    with insufficient permissions when opening a file in some specified

  - Opening an IO space using a handler <zero> now provides an IO
    space of size 2^64 bytes whose contents are all zero bytes, and that
    ignores any writes to it.  Example:

    | var zeroes = open ("<zero>");

  - New IO device sub for sub-spaces.  Sub IO spaces that act like a
    (maybe) narrower version of some other given IO space can be opened
    using a sub:// handler.  Example:

    | var sub = open ("sub://2/0x10/0x1000/somename", IOS_M_RDONLY);

    This will create a sub-space that provides read-only access to the
    [0x10#B,0x1010#B] range of bytes of some other IO space with id #2.

    Since it can be annoying to format the handler string, a convenient
    utility function called opensub has been added to the standard

    | var sub = opensub (ios, 0x10#B, 0x1000#B, "somename", IOS_M_RDONLY);

  - New IO device proc for poking at the memory of live processes.  The
    handler to pass to open in order to poke at the memory of a process
    with a given PID has the form pid://PID.  Example:

    | var fd = open ("pid://1234");

    Since it can be annoying to format the handler string, a convenient
    utility function called openproc has been added to the standard

    | var fd = openproc (1234);

Terminal hyperlinks updates

  - The payload used in the terminal hyperlinks URL is now reduced to a
    token number.  This makes it more opaque and compact than the
    previous version where we would encode full Poke expressions in the

  - The "hyperserver", poke utility subsystem that provides and handles
    the support for "terminal hyperlinks", has been partially rewritten.
    The new implementation is mostly written in Poke.  This makes it
    possible for Poke programs (like pickles) to emit and handle
    terminal hyperlinks.  For example:

    | var url = hserver_make_hyperlink ('e', "2 + 2");
    | term_begin_hyperlink (url, "");
    | print ("[clickme]");
    | term_end_hyperlink;

    Will print a clickable button "[clickme]" in the terminal, which
    once clicked on will execute the Poke code "2 + 2".

  - poke 1.x supported two variants of terminal hyperlinks: "execute"
    and "insert".  Clicking on an "execute" hyperlink triggers the
    execution of some given textual Poke expression or statement.
    Clicking on an "insert" hyperlink triggers the inclusion of some
    given string at the current input position at the prompt.  We now
    introduced a third kind of hyperlinks: the "closure" hyperlinks.
    Once clicked, some given Poke closure/function gets executed.  This
    is particularly useful when generating hyperlinks from a Poke
    program.  For example:

    | fun toggle_setting = void: { ... };
    | term_begin_hyperlink (hserver_make_hyperlink ('c', "", (toggle_setting)), 
    | print "[toggle]";
    | term_end_hyperlinks;

    will print a clickable button "[toggle]" in the terminal, which once
    clicked on will execute the toggle_setting function.

libpoke updates

  - poke now installs a pkg-config file poke.pc to ease using libpoke.

  - libpoke now provides an interface to register foreign IO spaces.
    This allows adding pokeish capabilities to third-party programs.  As
    an example, poke integration in GDB has been written (not upstreamed
    yet) that makes it possible to poke the memory of an inferior
    process being debugged.  This is achieved by registering callbacks
    in the foreign IO interface.

  - libpoke now provides an inteface to register "alien tokens".  This
    is also useful when integrating libpoke in third-party applications.
    For example, in the GDB integration this interface has been used to
    allow users to refer to the value of GDB symbols in Poke programs
    using this syntax:

    | $main

    and to the address of a given symbol using this syntax:

    | $addr::main

  - It is now possible to create an incremental compiler without
    standard types.  This is useful in cases where the program
    integrating with libpoke provides its own concept of types like int
    or long.  This is the case of GDB.

  - We added more services in libpoke to operate on PK values.  Many
    more still need to be added.

  - libpoke.h is now C++ compatible.

Pickles updates

  - New pickle provides definitions to poke ASN-1 data
    encoded in BER (Basic Encoding Rules.)

  - New pickles provides definitions to poke USTAR file
    systems, standardized by POSIX.1-1988 and POSIX.1-2001.

  - New pickles provides functions that dump the data of CTF
    sections in a human-readable form.  Contributed by Indu Bhagat on
    behalf of Oracle Inc.

  - New pickles provides definitions to poke JFFS2 file

  - The pickle has been splitted in 32-bit and 64-bit variants,
    and ELF-32 definitions have been added.

  - The output messages emitted by have been improved.

  - New tests for the pickle.  Contributed by David Faust on
    behalf of Oracle Inc.

Utilities updates

  - New filter
  - New filter

Development tools updates

  - RAS (the retarded poke assembler) now allows to split long logical
    lines into several physical lines by finishing them with the
    backslash character.  This is an example:

    | .macro struct_field_extractor @struct_type @field @struct_itype \
    |                               @field_type #ivalw #fieldw

  - RAS now understands the endianness specifiers IOS_ENDIAN_LSB and
    IOS_ENDIAN_MSB.  Better than hardcoded magic numbers.

  - RAS now emits an error if it finds a .function in which there is not
    exactly one prolog instruction and at least one return instruction.
    This problem has bitten me very often, resulting in very puzzling
    and subtle bugs, glglgl.

Notable bug fixes

  - The infamous, annoying, hated and despised "PVM_VAL_CLS_ENV
    (closure) != NULL" bug has (most probably... crossing fingers, toes
    and whatnot) been finally fixed in this release.  I have tried no
    less than eight times to fix this bug, but not until very recently I
    finally understood what was going on; I thought I did and the test
    case would work, but no I didn't and the bug would soon return with
    renovated hatred.  On my defense, the involved area is the hairiest
    part of the code generator and every time I look at it I basically
    have to re-learn how it works.  Good news is: if the same problem
    manifests again, now we know how to fix it.  But hopefully it is
    fixed now and I will stop receiving hate email about this.

  - --disable-hserver now actually disables the hyperserver.  Yes,

Documentation updates

  - We have added a new online help system to the poke utility, which is
    accessible using the .help dot-command.  There are help entries for
    all the commands, dot-commands and global settings.  This new online
    help system is written in Poke, making it possible to other Poke
    programs (like pickles) to add their own help topics to the system.

  - We have expanded the user manual to cover the new functionality and
    clarify obscure concepts that weren't explained with enough clarity.
    Despite of this work, the user manual is not yet complete,
    unfortunately, but getting there.

  - The user manual now contains a section that explains how to set up
    your system and terminal emulators to support poke terminal

  - There is a new website called Pokology,,
    which is maintained by the poke developers and users.  It is a live
    repository of knowledge relative to GNU poke, including practical
    articles, multimedia stuff, hints and tricks, a frequently asked
    question, etc.

Editor support updates

  - The Emacs modes poke-mode, poke-ras-mode and poke-map-mode have been
    update with more features and bug fixes.

  - We now distribute a module for Poke syntax highlighting for vim.
    Contributed by Matthew T. Ihlenfield.

Other updates

  - We have rewritten the way global settings (like endianness,
    numeration base used for output, etc) are handled in both libpoke
    and the poke application.  The new implementation introduces a
    "settings registry" which is written itself in Poke.  As such, other
    Poke code (like pickles and the like) have full access to the
    settings registry, and even add their own settings to the

  - Many improvements in compiler error messages.  This includes
    emitting more meaningful messages, for example "got int<32>
    expected string" instead of "invalid operands in expression".  And
    also better locations, like pointing at the particular operand whose
    type is wrong instead of the entire expression.

Happy poking!

Jose E. Marchesi
Frankfurt am Main
28 February 2022

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