Re: Building mozart-gtk on powerpc [request for help]

[Albert Cahalan <albert@users.sf.net>]

On Wed, 2004-08-25 at 07:52, Kevin Glynn wrote:
> Daniel Kobras writes:
>  > On Tue, Aug 24, 2004 at 06:21:57PM +0200, Kevin Glynn wrote:
>  > > fyi, it is because va_list is declared as a one-element array of
>  > > structs on powerpc, unlike other architectures so code like:
>  > > 
>  > > va_list Arg4 = (va_list) OZ_getForeignPointer((*(_OZ_LOC[(4)])));
>  > > 
>  > > fails on powerpc, because you can't cast to an array.
>  > 
>  > And you may not assign to a va_list. Use va_copy() instead to be
>  > portable.
>  > 
>  > Daniel.
>  > 
> 
> I don't see how va_copy will help me.  OZ_getForeignPointer(...)
> returns a void*, so I will still need to cast it to a va_list to be
> able to call va_copy. Here is my test program, perhaps you can suggest
> an alternative:

Due to some disgusting changes in the C standard,
casting from (void*) is pretty much illegal anyway.
I expect that C++ is affected as well. It has to
do with pointer aliasing.

Use a union. Put all the types you need into the
union. So you'd use a pointer to a union, and skip
the casting.

Use the -Wstrict-aliasing=2 compiler option.

I use:

  -W -Wall -Wshadow -Wcast-align -Wredundant-decls \
  -Wbad-function-cast -Wcast-qual -Wwrite-strings -Waggregate-return \
  -Wstrict-prototypes -Wmissing-prototypes \
  -Wdeclaration-after-statement -Wpadded -Wstrict-aliasing=2

(those last 3 depending on a recent gcc)