mes/HACKING

                                                              -*- org -*-
#+TITLE: Hacking GNU Mes

Copyright © 2016, 2017,2018 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>

  Copying and distribution of this file, with or without modification,
  are permitted in any medium without royalty provided the copyright
  notice and this notice are preserved.

* SETUP
    guix environment -l .guix.scm     #64 bit + 32bit

or

    guix environment --system=i686-linux -l .guix.scm #32 bit only

or

    guix package --profile=~/.config/guix/mes --manifest=build-aux/manifest.scm
    . ~/.config/guix/mes/etc/profile

* BUILD
There are two major modes to build Mes: true bootstrap and
development.

** DEVELOPMENT BUILD
To help development we assume ./configure sets these variables for make

   CC     -- gcc
   CC32   -- i686-unknown-linux-gnu-gcc (or on x86, also gcc)
   GUILE  -- guile
   HEX2   -- hex2
   MES    -- unset
   M1     -- M1
   prefix -- ""

Mes is supposed to serve as a full equivalent for Guile, however Mes
~30 times slower than Guile.  That's why we usually don't use Mes
during development.

Gcc is used to verify the sanity of our C sources.

i686-unknown-linux-gnu-gcc is used to compare hex/assembly, to test
the gcc variant of Mes-libc: lib/libc-gcc.c and steal ideas.  Target
prefix: mlibc-gcc.

Guile is used to develop MesCC, the C compiler in Scheme that during
bootstrapping will be executed by Mes.

mes is built from src/*.c and some out/src/*.h files that are snarfed from
src/*.c by build-aux/mes-snarf.scm.

Running ./make.scm produces a `script' file.

** BOOTSTRAP BUILD

    ./build.sh

In bootstrap mode, we don't have gcc (CC), we don't have a 32 bit gcc
(CC32), we have no guile (GUILE)...but we should have hex2, M1, and
mes.M1.  That's a bootstrap problem which is currently ignored by
using the mes-seed package.  mes.M1 will be produced by M2-Planet from
mes.c.


* ROADMAP
** TODO
*** release 0.x, unsorted
  - upstream mes-boot to GuixSD.
  - replace GuixSD bootstrap for x86.
  - replace bootstrap utils (with gash?): flex, bash, bzip2,
    coreutils, diffutils, gawk, grep, gzip, make, sed, tar.
  - tcc: remove or upstream patches from tcc-boot.
  - tcc: build 0.9.27 directly instead of via 0.9.26,
    see tinycc wip-bootstrappable@0.9.27 branch
  - mes: prepare src/mes.c for M2-Planet transpiler,
    Jeremiah branched-out from mes; see https://github.com/oriansj/mes-m2.
  - mes: real module support, bonus for supporting Guile's define-module/define-public syntax.
  - mes: we're a full Scheme now, drop .MES suffix, use .SCM.
    + find a way to fix foo.mes/foo.scm trickery (full Guile-like module support?) + how about setting `guile' or even `guile-2' cond-expand features
      for external libraries (Nyacc) we look like Guile/Guile-2
      internally, we could make sure to start every cond-expand with (mes)
  - mes: use more efficient scheme continuation stack (wip-array?)
  - mes: drop SCM stack in C / implement call/cc a la guile-1.8 setjmp?
  - mes/mescc: bootstrap a minimal-Guile
    + libguile/{eval,init,list,strings,values,..}.c
    + ice-9/eval.scm
  - mescc: have mes-tcc pass all scaffold/tests, scaffold/tinycc tests.
  - mescc: support long long.
  - mescc: full support for floats?
  - mescc: some success with 8cc,pcc,guile/libguile/eval.c.
  - build: guile/guix/make.scm: add file-types, intermediate, hash all dependencies
  - build: make.scm: imperative->declaritive
  - get full source syntax-case up (Andre van Tonder?) OR drop it.
    https://srfi.schemers.org/srfi-72/srfi-72.html
    psyntax/syntax-case and rewrite Nyacc without syntax-case+R7RS Ellipsis.
  - mescc: split-off MesCC as as standalone Guile C compiler project.
*** release 1.0
  - replace GuixSD's bootstrap binaries for x86.
  - add x86_64, replace GuixSD's bootstrap binaries for x86_64.
  - more architectures (does GuixSD require this, i.e. before 1.0?).
** DONE
*** 0.17 GNU Mes is now an official GNU project and bootstraps gcc-4.7.4.
*** 0.16.1 Mes now has info docs and installs ootb on Debian buster/testing.
*** 0.16 Mes Lib C now bootstraps glibc-2.2.5, binutils-2.20.1, gcc-4.1.0.
*** 0.15: MesCC now has a libc+gnu that supports compiling binutils-2.14, gcc-2.95.3 and glibc-2.2.5.
*** 0.14: Mes+MesCC now compiles a slightly patched self-hosting tcc.
*** 0.13: Mes+MesCC now compiles a modified, functional tcc.c (~25,000LOC) in 1h30'.
*** 0.12: Mes+MesCC now compiles mes.c (~3000LOC) in ~4min.
*** 0.11: MesCC now compiles a mes-tcc that passes 26/69 of mescc's C tests.
*** 0.10: Mescc now compiles a mes-tcc that compiles a trivial C to a running a.out.
*** 0.9: Mescc now writes M1 macro assembly files and compiles tcc.
*** 0.8: Mescc now writes object files in stage0's labeled hex2 format.
*** 0.7: Mescc supports -E, -c, -o options, include more complete set of header files,
enough to work on compiling tinycc's tcc.c albeit a somewhat modified version.
*** 0.6: Work with unmodified, unbundled Nyacc; compile 33/55 tinycc's tests/test2 suite.
*** 0.5: Mutual self-hosting Scheme interpreter and C compiler: mes.c and mescc,
         Support call-with-current-continuation, refactor catch/throw
*** 0.4: Support Nyacc, Gcc-compiled Mes compiles minimal main.c using nyacc
*** 0.3: Garbage collector
*** 0.2: Support psyntax
*** 0.1: Mes eval/apply feature complete; support syntax-rules, compile main.c using LALR, dump ELF


* DEBUG
  MES_DEBUG=<level> mes
** Levels
  1) Informational:
     - MODULEDIR
     - included SCM modules and sources
     - result of program
     - gc stats at exit
  2) opened files
  3) runtime gc stats
  4) detailed info
     - parsed, expanded program
     - list of builtins
     - list of symbol
     - opened input strings
     - gc details
  5) usage of opened input strings


* Bugs
** mes: gcc-x86 compiled, tests/srfi-13.test number->string INT-MIN fails:
test: number->string INT-MIN: fail
expected: -2147483648
actual: -./,),(-*,(
** tcc: tcc-built lib/libc+tcc.c segfaults with mes, with tcc.
** mes: remove pmatch-car/pmatch-cdr hack.
** mescc: softcode stack frame size, now hardcoded and very large
** mes+mescc: parse tcc.c->tcc.E works, compile tcc.E -> tcc.M1 segfaults.
  time GUILE_LOAD_PATH=/home/janneke/src/nyacc/module:$GUILE_LOAD_PATH ../mes/scripts/mescc -E -o tcc.E -I . -I ../mes/lib -I ../mes/include -D 'CONFIG_TCCDIR="usr/lib/tcc"' -D 'CONFIG_TCC_CRTPREFIX="usr/lib:{B}/lib:."' -D 'CONFIG_TCC_ELFINTERP="/gnu/store/70jxsnpffkl7fdb7qv398n8yi1a3w5nx-glibc-2.26.105-g0890d5379c/lib/ld-linux.so.2"' -D 'CONFIG_TCC_LIBPATHS="/home/janneke/src/tinycc/usr/lib:{B}/lib:."' -D 'CONFIG_TCC_SYSINCLUDEPATHS="../mes/include:usr/include:{B}/include"' -D CONFIG_USE_LIBGCC=1 -D 'TCC_LIBGCC="/home/janneke/src/tinycc/usr/lib/libc+tcc-gcc.mlibc-o"' -D CONFIG_TCC_STATIC=1 -D ONE_SOURCE=yes -D TCC_TARGET_I386=1 -D BOOTSTRAP=1 tcc.c
  time GUILE_LOAD_PATH=/home/janneke/src/nyacc/module:$GUILE_LOAD_PATH MES_ARENA=200000000 ../mes/scripts/mescc -c -o tcc.M1 tcc.E
** mes: with-fluids: tests/fluids.test test 7 fails with Mes.
** mescc: 7n-struct-struct-array.c:  struct file f = {"first.h"};
** test/match.test ("nyacc-simple"): hygiene problem in match
* OLD: Booting from LISP-1.5 into Mes

Mes started out experimenting with booting from a hex-coded minimal
LISP-1.5 (prototype in mes.c), into an almost-RRS Scheme.

When EOF is read, the LISP-1.5 machine calls loop2 from loop2.mes,
which reads the rest of stdin and takes over control.  The functions
readenv, eval and apply-env in mes.mes introduced define, define-macro
quasiquote and macro expansion.

While this works, it's amazingly slow.  We implemented a full reader
in mes.c, which makes running mes:apply-env mes:eval somewhat
bearable, still over 1000x slower than running mes.c.

Bootstrapping has been removed and mes.c implements enough of RRS to
run a macro-based define-syntax and syntax-rules.

loop.mes and mes.mes are unused and lagging behind.  Probably it's not
worth considering this route without a VM.  GNU Epsilon is taking the
more usual VM-route to provide multiple personas.  While that sounds
neat, Lisp/Scheme, bootstrapping and trusted binaries are probably not
in scope as there is no mention of such things; only ML is mentioned
while Guile is used for bootstrapping.

* Assorted ideas and info
** Using GDB on assembly/a.out
info registers
p/x $eax
p/x $edx
set disassemble-next-line on
gdb-display-disassembly-buffer
b *0x804a79d
** Create memory dump with 32 bit Gcc compiled Mes
make out/i686-unknown-linux-gnu-mes
out/i686-unknown-linux-gnu-mes --dump < module/mes/read-0.mes > module/mes/read-0-32.mo
** C parser/compiler
*** [[https://savannah.gnu.org/projects/nyacc][nyacc]]
*** PEG: [[http://piumarta.com/software/peg/][parse C using PEG]]
*** [[https://en.wikipedia.org/wiki/Tiny_C_Compiler][Tiny C Compiler]]
*** [[http://www.t3x.org/subc/index.html][Sub C]]
*** [[https://groups.google.com/forum/#!topic/comp.lang.lisp/VPuX0VsjTTE][C intepreter in LISP/Scheme/Python]]

** C assembler/linker
*** [[http://www.tldp.org/HOWTO/Assembly-HOWTO/linux.html][Assembly HOWTO]]
*** ELF
7f 45 4c 46
*** [[http://www.muppetlabs.com/~breadbox/software/tiny/][Small ELF programs]]
*** [[http://www.cirosantilli.com/elf-hello-world/][Elf hello world]]
** SC - c as s-expressions
sc: http://sph.mn/content/3d3
** RNRS
*** [[http://www.scheme-reports.org/][Scheme Reports]]
*** [[ftp://publications.ai.mit.edu/ai-publications/pdf/AIM-349.pdf][Scheme - Report on Scheme]]
*** [[ftp://publications.ai.mit.edu/ai-publications/pdf/AIM-452.pdf][RRS - Revised Report on Scheme]]

** tiny schemes
http://forum.osdev.org/viewtopic.php?f=15&t=19937

http://www.stripedgazelle.org/joey/dreamos.html
http://armpit.sourceforge.net/
http://common-lisp.net/project/movitz/movitz.html

<civodul> janneke: https://github.com/namin/inc looks interesting  [15:18]
** Orians Jeremiah
<OriansJ> janneke: also, if you look at
          https://github.com/oriansj/stage0/tree/master/stage2/High_level_prototypes
          [the garbage collected lisp I implemented], if there are any pieces
          I could add to finish off your mes lisp bootstrap just let me know
          because I would be more than happy to do that :D
<janneke> OriansJ: that's what I'm hoping for, that our efforts can be
          complementary and we can work together
*** lfam (~lfam@2601:47:4180:2ffb:7c05:17de:cf5f:23ef) has quit: Ping timeout:
    246 seconds  [00:22]
<janneke> exciting times!  [00:23]
<janneke> OriansJ: i looked a few times and saw 'LISP empty', so thanks for
          the pointer!  [00:24]
<civodul> OriansJ, janneke: from that page, there's also:
          https://web.archive.org/web/20160604035203fw_/http://homepage.ntlworld.com/edmund.grimley-evans/bcompiler.html

** C4/C500
https://web.archive.org/web/20160604041431/http://homepage.ntlworld.com/edmund.grimley-evans/cc500/cc500.c
https://github.com/rswier/c4/blob/master/c4.c
** Compilers for free
http://codon.com/compilers-for-free
** Small lisps
*** [[https://www.mirrorservice.org/sites/www.bitsavers.org/bits/TI/Explorer/zeta-c/][ZETA-C]]
** Small C compilers
*** tinycc
*** [[https://github.com/rui314/8cc][8cc]] -- a C11 compiler, but simple
8cc is a compiler for the C programming language. It's intended to
support all C11 language features while keeping the code as small and
simple as possible.
*** pcc
*** early GCC?
https://miyuki.github.io/2017/10/04/gcc-archaeology-1.html
*** [[http://tack.sourceforge.net/][ack]]
<rain1> it may be possible to compile like this:  mes |> ack |> pcc |> tcc |>
        gcc 4.7.4 |> gcc later version... up to modern
*** [[https://web.archive.org/web/20160402225843/http://homepage.ntlworld.com/edmund.grimley-evans/cc500/][cc500]]
** rain1's Bootstrapping Wiki: https://bootstrapping.miraheze.org/wiki/Main_Page
** rain1's hex86
https://notabug.org/rain1/hex86/src/master/tests/hex0b3.hex86