[C2hs] How to access inside a union using #set

[Benedikt Huber]

On 02.04.2009, at 09:42, Mark Wassell wrote:
> Hello,
>
> I have the following:
> ...
> typedef struct tagINPUT {
> DWORD type;
> union {MOUSEINPUT mi;
>           KEYBDINPUT ki;
>           HARDWAREINPUT hi;
>          };
> }INPUT, *PINPUT;
Hi Marc,

this is probably because c2hs does not (yet) support the 'Unnamed  
fields' extension (http://gcc.gnu.org/onlinedocs/gcc-4.3.3/gcc/Unnamed-Fields.html 
).

This works fine:

 > module Test where
 > #c
 > typedef struct {
 >   union { int x;  } u;
 > } S1;
 > #endc
 > test  = {#set S1.u.x #}

but this won't work:

 > module Test where
 > #c
 > typedef struct {
 >   union { int x;  };
 > } S2;
 > #endc
 > test  = {#set S2.x #}

If you care about a fix, please file a bug at http://hackage.haskell.org/trac/c2hs/wiki

cheers, benedikt

>
>
> and in a chs file:
>
> sendChar :: HWND -> Char -> IO ()
> sendChar win ch = do
>                     allocaBytes ( {#sizeof INPUT#}) $ \ptr ->
>                       {#set INPUT.type #} ptr 0
>                       {#set INPUT.ki.wVk #} ptr 0
>                       {#set INPUT.ki.dwFlags #} ptr 0
>
> c2hs comes up with
>
>
> Test1.chs:27: (column 37) [ERROR]  >>> error
> Unknown member name!
> The structure has no member called `ki'.  The structure is defined at
> ("sendinput.h",35,9).
> Test1.chs:26: (column 37) [ERROR]  >>> error
> Unknown member name!
> The structure has no member called `ki'.  The structure is defined at
> ("sendinput.h",35,9).
>
> How do I address fields inside the union?
>
> Cheers
>
> Mark
>
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