Re: GEC Compilation of Externals

I wrote:

> I seem to remember trying this and it didn't work in some cases.
> It's been a while. I'll try it again when I get a chance.
> 
> Brian

I remember now. I figured out how to make statements work with all
three compilers by adding a semi-colon, just as you suggested. What I
couldn't figure out were functions, for example:

sizeof: INTEGER is
    -- Size to allocate (in bytes)
  external
    "C inline use <windows.h>"
  alias
    "sizeof (struct _COMMTIMEOUTS)"
  end

becomes

/* COM_TIMEOUTS.sizeof */
T4 T78f6(T0* C)
{
  T4 R = 0;
sizeof (struct _COMMTIMEOUTS)
  return R;
}

for GEC. While SE generates the following code:

/*COM_TIMEOUTS*/
T2 r232sizeof(se_dump_stack*caller){
T2 R=0;
...
R=(sizeof (struct _COMMTIMEOUTS));
...
return R;
}

and ISE generates the following code:

EIF_INTEGER_32 Fa9f3k0 (EIF_REFERENCE Current)
{
...
  EIF_INTEGER_32 Result = (EIF_INTEGER_32) 0;
...
  Result = (EIF_INTEGER_32)(sizeof (struct _COMMTIMEOUTS));
...
  return Result;
}

Eric, you mentioned implementing externals according to the ECMA
specification. I agree that you have done that, but I don't think the
inline mechanism is not specified well (from ECMA-367):

8.31.14 Semantics: C Inline semantics
In an external routine er of the inline form, an External_name of the
form alias C_text denotes the algorithm defined, according to the
semantics of the C language, by a C function that has:
• As its signature, the signature specified by er.
• As its body, C_text after replacement of every occurrence of $a,
where the lower name of a is the lower name of one of the formal
arguments of er, by a.

When implementing a function, simply replacing C_text will not do. A
return statement is necessary. In addition, consider the following
example from ETL3 (http://se.inf.ethz.ch/~meyer/ongoing/etl/others.pdf
para 31.11):

an_inline_function (x,y: INTEGER): INTEGER
  external "[
    C
      inline
      use <stdio.h>
    ]"
  alias "[
    if ($x > 5) {
      some_c_function ($y, cvar++);
    }
  ]"
end

This can't work because C_text does not return a value as the
signature of `an_inline_function' suggests it should.

Brian






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