[m-dev.] diff: pragma c_code fix

[Tyson Dowd]

On 09-Nov-2000, Peter Ross <peter.ross at miscrit.be> wrote:
> Hi,
> 
> 
> ===================================================================
> 
> 
> Estimated hours taken: 1
> 
> mercury/compiler/llds_out.m:
>     Output any `pragma c_code' first for the LLDS backend.  This is
>     because variables may be defined in a `pragma c_code' and we want
>     the definition to appear before any use of the variable.  Also
>     output the `pragma c_code' fragments in the same order they appear
>     in the source file, as this is the more intuitive behaviour.

I don't think this is the right approach to take.  In fact, I think this
is broken.

If you want to declare variables in the c_code that can be referenced
from any place in the module, use pragma c_header_code, and put an
extern declaration in for the variable.  Declarations should go in the
c_header code, definitions in c_code.  (Perhaps the documentation should
be clearer on this issue?).

Then it doesn't matter *where* you put the actual definition of the
variable.

That way you can use --split-c-files and even if every procedure is put
in a separate file, they can all see the c_header_code, and know there
will be a variable defined somewhere to link to.

Your change will just hide this problem -- the code will work fine when
in a single file but cannot be split into separate files without
breaking.

-- 
       Tyson Dowd           # 
                            #  Surreal humour isn't everyone's cup of fur.
     trd at cs.mu.oz.au        # 
http://www.cs.mu.oz.au/~trd #
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