Re: [ooc-compiler] Type Constructors and Export Marks

[Stewart G. <sgr...@ii...>]

Hi August,

Looks like you found a bug.

For me, the compiler accepts that module. The error is from the C 
compiler during code generation.

obj/M.d:4: error: conflicting types for 'M__x'
obj/M.oh:11: error: previous declaration of 'M__x' was here
obj/M.d:4: error: conflicting types for 'M__x'
obj/M.oh:11: error: previous declaration of 'M__x' was here

I think there is a slight problem with the output of type declarations. 
In this case, "x" is exported, so oo2c needs to generate an "extern" 
declaration for "x" in M.oh (public headers for module M). Although it 
is the same declaration, this conflicts with the local declaration of 
"x" in M.d (private headers for module M). This is because C uses name 
equivalence, not structural equivalence for records. Its probably not a 
problem for other type constructors (eg. pointers, arrays) because they 
use structural equivalence in C.

What oo2c needs to do is to output a separate declaration for the type 
of "x" in M.oh. Normal Oberon-2 style is to declare names for most 
types, which is possibly why this problem has not been noticed.
For example:
   MODULE M;
      TYPE T = POINTER TO RECORD y-: LONGINT END;
      VAR x-: T;
   END M.
In this case you already have a declaration for the type, which is used 
for both variable declarations in the C code. Especially for records, 
you need a name for the type in order to pass the record type by 
reference (eg. as a VAR parameter), or to extend the record type.

Cheers,
   Stewart

August Karlstrom wrote:
> Hi,
> 
> Is the following module is invalid?
> 
>    MODULE M;
>       VAR x-: POINTER TO RECORD y-: LONGINT END;
>    END M.
> 
> OOC 2.1.9 thinks it is. Why?
> 
> 
> Regards,
> 
> August
> 
> 
> 
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