On Tuesday, 14 August 2012 at 20:10:13 UTC, Simen Kjaeraas wrote:
On Tue, 14 Aug 2012 21:27:25 +0200, Andrew
<[email protected]> wrote:
I'm trying to interface with C code, where I have a function
definition that takes two const char[]'s:
PetscErrorCode PetscInitialize(int*, char***, const char[],
const
char[]);
However, the typical way that you pass "Null" values instead of
the last two arguments is "PETSC_NULL"
The problem is that PETSC_NULL is a macro defined to be 0. I
can't do the normal "int PETSC_NULL = 0" thing, because it
doesn't follow the type signature of PetscInitialize.
How to I pass 0 in place of the last two arguments? cast(const
char[])(0) doesn't work, and just an empty string ("\0")
doesn't
work either.
-Andrew
I'm a tad confused. Why can't you just pass null? In D, the
literal
0 is not implicitly convertible to void*, char***, or any other
pointer or reference type, so instead you should use the literal
null, which has no nameable type, but is implicitly converted to
any pointer or reference type you may wish.
If you really want to, you can have
enum PETSC_NULL = null;
so that you can write PetscInitialize( &i, PETSC_NULL,
PETSC_NULL ),
but I'd recommend just using the null we have.
This appears to be the correct answer. I was mostly just
confused. something #defined is just replaced by the C
preprocessor (or so I thought), which means that in C, you would
be passing 0 to PetscInitialize... which seems weird.
passing null seems to work though.
-Andrew
