88 lines
3.5 KiB
Plaintext
88 lines
3.5 KiB
Plaintext
Subject: on bootstrapping: 2nd status report on Mes
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Date: Sun, 25 Sep 2016 13:52:11 +0200
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Hi!
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In June I announced[0] Mes as a project that seeks to reduce the size of/
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dependency on bootstrap binaries, esp. for a system like GuixSD
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The strategy was to create a minimal trusted binary (prototyped in C but
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eventually to be hand-crafted in assembly/hex) that interpets a minimal
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LISP. Then using this minimal but already convenient LISP, extend it
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into Scheme and write a tiny C compiler/linker.
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Last time I had a minimal LISP-1.5-resembling interpreter in 900 lines
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of C that could interpret itself and an extension layer written in LISP
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providing a minimal Scheme environment. I was stuck on adding macros in
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LISP and had a broken macro implentation in C that I wanted to remove.
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Also I hoped to greatly reduce the size of the C part.
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New status[1]
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* Provide Scheme primitives directly in 1400 lines of C
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* Remove LISP-1.5 staging
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* closures clue-bat, fixing bugs in begin, lambda, lexical
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scoping etc. ... learned a lot!
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* quasiquote, unquote, unquote-splicing (in C, too slow in Scheme)
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* define-macro (in C)
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* define-syntax, syntax-rules (in Scheme, using define-macro)
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* all primitives needed to run LALR (strings, vectors, records,
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some srfi bits; mostly in Scheme)
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* test suite with 97 tests that run with Mes and also with Guile
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* minimal and partial ANSI C parser for hello world
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* minimal and simplistic 32 bit elf c-ast->elf generator
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Mes can now create a running 32-bit elf binary from this hello
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world C source with a simplistic for loop
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int main ()
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{
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int i;
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puts ("Hi Mes!\n");
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for (i = 0; i < 4; ++i)
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puts (" Hello, world!\n");
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return 1;
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}
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It takes Mes 1'20" to compile this program, Guile takes 0.5 seconds.
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* cannot get psyntax.pp hooked-up or running
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* do not understand syntax stuff [well enough] to implement in C
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-> no let-syntax, no MATCH
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-> no syntax-case, no PEG parser
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In theory the bootstrapping problem I set out to solve seems to be
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cracked. The remaining problem is reduced to `just work':
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implementing a minimal C compiler in Scheme. Questions here: I'm not
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convinced yet that this is a meaningful project...aaand I really not
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want to tackle this without having MATCH, which Mes does not have yet.
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Of the possible directions that I see
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0 write the C compiler in Scheme without match
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1 rewrite match without let-syntax
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2 grok+write let-syntax/syntax-case using define-macro, some bits in C
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3 run and hook-up psyntax.pp...BUT that would probably require:
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4 address performance problem, possibly by
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5 rewrite Mes into a VM-based solution
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none I find really attractive. Option 5, a VM is proven to work but
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that's quite a change of direction. Looking at other VM-based projects
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(e.g. GNU Epsilon[2]) I fear that this must result in a much larger code
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base in C, throwing out the minimal trusted binary idea. The other
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puzzles and work 0, 2 or 3 still need to be done.
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However, diving into syntax-macro or eval work (2 or 3) most probably
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needs the performance issue addressed. And if it turns out that a big
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VM solution is needed, that may still invalidate this project after
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having done even more work.
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Help! :-) Ideas?
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Greetings,
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Jan
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[0] https://lists.gnu.org/archive/html/guile-user/2016-06/msg00061.html
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[1] https://gitlab.com/janneke/mes
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[2] http://git.savannah.gnu.org/cgit/epsilon.git
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