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Re: ffi-help: status to 19 Aug 2017

From: Matt Wette
Subject: Re: ffi-help: status to 19 Aug 2017
Date: Thu, 9 Nov 2017 17:00:23 -0800

> On Nov 9, 2017, at 11:10 AM, Roel Janssen <address@hidden> wrote:
> Matt Wette writes:
>> Hi All,
>> I am working on a ffi-helper: a program that will read in a C dot-h file and 
>> generate a Guile dot-scm file 
>> which defines a module to provide hooks into the associated C library.  Goal 
>> is to release something in
>> Oct 2017 but that date is likely to slip.
>> Current shortcomings:
>> 1) Guile does not currently handle some types (e..g, long long, uintptr_t).
>> 2) Guile does not have support for varargs (e.g., printf(char *, ...) ).
>>   I may take a look at this.  One idea I have is to use '... in the call 
>> interface spec
>>   and use (type . value) pairs in the calls.
>> 3) The bytestructures module does not support function declarations.
>> 4) ... (probably more)
>> Someone asked to have libgit2 converted and this, and some others, turned 
>> out to give visibility
>> to several limitations and bugs in my C parser.  For one, how #include 
>> <foo/bar.h> is interpreted 
>> is not specified by the language: it is implementation defined, and I had to 
>> track down how libgit2 
>> was including files.  I also had to add some GNUC extensions (e.g., asm, 
>> statement-block expressions,
>> include_next) to the parser and preprocessor.  As one can see from the file 
>> listing below, libgit2 
>> has a large number of files, and declarations.
>> ...
> Thanks for creating this!  It seems to be very useful and powerful.
> I wanted to try ffi-helper on htslib, but I am confused on how to get
> started.  Where does the "compile-ffi" subcommand for "guild" come from?
> Kind regards,
> Roel Janssen

See the following, but I'm seeing a parse error so may be a bug in my C99 
parser.  And not sure "hts.h" is the only include you need.

mwette$ git clone -b c99dev git:// nyacc
Cloning into 'nyacc'...
remote: Counting objects: 5927, done.
mwette$ cd nyacc
mwette$ cd examples
mwette$ source
mwette$ cd ffi
mwette$ cp TMPL.ffi htslib.ffi
mwette$ vi htslib.ffi
mwette$ cat htslib.ffi
;; htslib.ffi                           -*- Scheme -*-

(define-ffi-module (ffi htslib)
  #:pkg-config "htslib"
  #:include '("htslib/hts.h")
  #:inc-filter (lambda (file-spec path-spec)
                 (string-contains path-spec "htslib/" 0))

;; --- last line ---
mwette$ guild compile ffi/htslib.fif
;;; note: auto-compilation is enabled, set GUILE_AUTO_COMPILE=0
;;;       or pass the --no-auto-compile argument to disable.
;;; compiling /var/tmp/yy/nyacc/examples/scripts/compile-ffi.scm
;;; compiled .../c99/ffi-help.scm.go
TODO: fix gen-lookup-proc: it's including imported symbols
;;; scripts/compile-ffi.scm:119:8: warning: possibly unbound variable `compile'
;;; compiled 
ffi-help: WARNING: the FFI helper is experimental
/opt/local/include/htslib/hts.h:774: parse failed at state 313, on input "U"
(unknown):1: C99 parse error
*** compile-ffi: parse failed

The offending line is the following, which seems to indicate my lexer is not 
reading "LLU" constants. I will check.

    v = ((v & 0x00000000FFFFFFFFLLU) << 32) | (v >> 32);

Had the above worked, then you should be able to `(use-modules (ffi htslib))':

mwette$ guile
GNU Guile 2.2.2
Copyright (C) 1995-2017 Free Software Foundation, Inc.

Guile comes with ABSOLUTELY NO WARRANTY; for details type `,show w'.
This program is free software, and you are welcome to redistribute it
under certain conditions; type `,show c' for details.

Enter `,help' for help.
scheme@(guile-user)> (use-modules (ffi htslib))
ERROR: no code for module (ffi htslib)

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