MacOS mzc --embedded problems

[Matthew Flatt <mflatt@cs.utah.edu>]

Quoting Patrick Hertelendy:
> I tried compiling a scheme source file with mzc and the -o and -embbeded flags
> with CodeWarrior 4.0 on a powermac.
> I get the following errors: is there something wrong in the scheme 
> source file or with CodeWarrior?
>
> [...]
> 
> Error   : data type is incomplete
> Arinetbuild1.c line 687   Scheme_Object * _consts_[0];

In this case, I'll be the compiler doesn't like zero-sized arrays.
Indeed, mzc isn't supposed to emit them, and I see the bug.

You can hack around the problem by including a string in your source
file (somewhere that won't get optimized away).

To actually fix the problem, change `emit-static-variable-fields!' in
plt/collects/compiler/vm2c.ss, line 168, so that it does nothing when
it's given an empty list:

 (define (emit-static-variable-fields! port l)
  (unless (null? l) ; <<<< ADDED <<<<<
     (fprintf port "  /* Write fields as an array to help C comiplers */~n")
     ...))

> Error   : undefined identifier 'scheme_fuel_counter'
> Arinetbuild1.c line 10271   { if ((scheme_fuel_counter -= 1) <= 0) 
> scheme_process_block(0); }

This is a bug in the MzScheme header files. It's specific to platforms
that use MzScheme's manual linking table (MacOS is such a platform).
It's also specific to compiling for embedding.

I've fixed the header for the next release. In line 824 in the file
plt/collects/mzscheme/include/scheme.h, the lines

 #if !SCHEME_DIRECT_EMBEDDED
 # ifndef MZ_REAL_THREADS
 #  ifdef LINK_EXTENSIONS_BY_TABLE
 #   define scheme_fuel_counter (*scheme_fuel_counter_ptr)
 #  endif
 # endif
 #endif

should be

 #ifndef MZ_REAL_THREADS
 # if !SCHEME_DIRECT_EMBEDDED
 #  ifdef LINK_EXTENSIONS_BY_TABLE
 #   define scheme_fuel_counter (*scheme_fuel_counter_ptr)
 #  endif
 # else
 extern int scheme_fuel_counter;
 # endif
 #endif

Hope that helps,
Matthew