[petsc-dev] removing PETSC_NULL from petsc-dev

[Jed Brown]

On Thu, Feb 7, 2013 at 9:56 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:

> I have removed the use of PETSC_NULL from all PETSc C code. Please
> remember to just use NULL in PETSc source code in the future (or Karl's
> script will find you).
>

I see you changed to

#define PETSC_IGNORE NULL

but kept

#define PETSC_NULL 0

Should the second be updated to

#define PETSC_NULL NULL

because it is stricter about passing PETSC_NULL for an integer argument?

Also, we could do something like this (properly guarded, of course):

__attribute__((deprecated)) PETSC_UNUSED
PETSC_STATIC_INLINE void PETSC_NULL_IS_DEPRECATED_JUST_USE_NULL() {};
#define PETSC_NULL           (PETSC_NULL_IS_DEPRECATED_JUST_USE_NULL(),NULL)

which can be used for any compiler that supports non-static statements in
declarations (everything but Sun and MSVC?) and has
__attribute__((deprecated)). This produces warnings like this under Clang

ex5.c:102:36: warning: 'PETSC_NULL_IS_DEPRECATED_JUST_USE_NULL' is
deprecated [-Wdeprecated-declarations]
  ierr       =
PetscOptionsGetReal(PETSC_NULL,"-par",&user.param,NULL);CHKERRQ(ierr);
                                   ^
/home/jed/petsc/include/petscsys.h:387:31: note: expanded from macro
'PETSC_NULL'
#define PETSC_NULL           (PETSC_NULL_IS_DEPRECATED_JUST_USE_NULL(),NULL)
                              ^
/home/jed/petsc/include/petscsys.h:385:33: note:
'PETSC_NULL_IS_DEPRECATED_JUST_USE_NULL' declared here
PETSC_UNUSED static inline void PETSC_NULL_IS_DEPRECATED_JUST_USE_NULL() {};
                                ^
1 warning generated.

and like this with GCC:

ex5.c: In function ‘main’:
ex5.c:102:3: warning: ‘PETSC_NULL_IS_DEPRECATED_JUST_USE_NULL’ is
deprecated (declared at /home/jed/petsc/include/petscsys.h:385)
[-Wdeprecated-declarations]


We can make the error message cleaner (but more confusing) with

__attribute__((deprecated))
PETSC_UNUSED static inline void PETSC_NULL() {};
#define PETSC_NULL           (PETSC_NULL(),NULL)

which produces:

ex5.c: In function ‘main’:
ex5.c:102:3: warning: ‘PETSC_NULL’ is deprecated (declared at
/home/jed/petsc/include/petscsys.h:385) [-Wdeprecated-declarations]


Any sense in this stuff?
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