[Developers] g++ warning: operation on *bla* may be undefined

[Steve White]

Hi again.

Unfortunately, Portland Group's C++ compiler (which I hadn't tried
in my tests) now warns:

      variable "parameter_name" was set but never used

for every CCTK parameter.  I don't think it was warning about the
old code.

It seems that one can't please everybody.


On 20.10.06, Steve White wrote:
> Hi,
> 
> This is concerned with g++ warnings like:
> 
> 	Preprocessing arrangements/Carpet/Carpet/src/Timing.cc
> 	Compiling arrangements/Carpet/Carpet/src/Timing.cc
> 	configs/chain_gcc_carpet/build/Carpet/Timing.cc:
> 		In function ‘void Carpet::InitTimingVariables(const cGH*)’:
> 	configs/chain_gcc_carpet/build/Carpet/Timing.cc:120:
> 		warning: operation on ‘cctki_use’ may be undefined
> 
> The culprit was in generated bindings code meant to get rid of warnings
> about unused variables corresponding to Cactus parameters included in
> code by the DECLARE_CCTK_PARAMETERS macro.
> 
> Typically, a struct was defined to hold copies of the macros, then
> such very interesting constructs would appear.
> 
>   const void *PRIVATE_CACTUS_STRUCT_use = ( \
>     PRIVATE_CACTUS_STRUCT_use = &cctk_run_title, \
>     PRIVATE_CACTUS_STRUCT_use = &*PRIVATE_CACTUS_STRUCT_use \
>   )
> 
> This code replaces that with a do-nothing enum declaration
>   enum {
>     dummy_cctk_run_title = sizeof( cctk_run_title )
>     //,etc.
>   };
> The nature of all the entities involved is here much clearer, both to
> compilers and to me.
> 
> Like the existing solution, this permits the user to proceed to make more
> declarations after the DECLARE_CCTK_PARAMETERS macro (simply putting a list
> of variable assignments after the declaration would not have that property).
> 
> See also the patches list posting of the same name, and PR 2070
> http://www.cactuscode.org/cactus_cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=cactus&pr=2070
> for a patch.
> 
> It has been tested on Gnu 4x, Intel 9x, IBM XL
> 
> Cheers!
> 

-- 
Steve White : Programmer
Max-Planck-Institut für Gravitationsphysik      Albert-Einstein-Institut
Am Mühlenberg 1, D-14476 Golm, Germany                  +49-331-567-7625