[m-dev.] `pragma export' C calling convention & polymorphism

[Fergus Henderson]

Hi,

What type should `pragma export' use for polymorphically typed
arguments -- `MR_Word' or `MR_Box'?  Currently it is schitzophrenic.
The reference manual says

 | 	Mercury variables of type `int', `float', `char', or `string'
 | 	are passed to and from C as C variables whose type is given by
 | 	the corresponding typedef.  Mercury variables of any other
 | 	type are passed as a `MR_Word'

but the compiler uses `MR_Box'.  This only makes a difference for
MLDS grades -- for LLDS grades, `MR_Box' is just a typedef for `MR_Word',
but for MLDS grades `MR_Box' is `void *', while `MR_Word' is an
unsigned integer type.

At some point we probably want to change the conventions used by
`pragma export' dramatically, to be something very similar to those
used by the current --high-level-data MLDS back-end.  But I don't want
to do that now.

So I guess for now the best solution is to go with what the reference
manual says, and treat the compiler's current behaviour as a bug?

-- 
Fergus Henderson <fjh at cs.mu.oz.au>  |  "I have always known that the pursuit
                                    |  of excellence is a lethal habit"
WWW: <http://www.cs.mu.oz.au/~fjh>  |     -- the last words of T. S. Garp.
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