PETSC_NULLPTR — PETSc 3.21.4 documentation

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# PETSC_NULLPTR

Standard way of indicating a null value or pointer No Fortran Support

## Notes

Equivalent to `NULL` in C source, and `nullptr` in C++ source. Note that for the purposes of interoperability between C and C++, setting a pointer to `PETSC_NULLPTR` in C++ is functonially equivalent to setting the same pointer to `NULL` in C. That is to say that the following expressions are equivalent:

      ptr == PETSC_NULLPTR
      ptr == NULL
      ptr == 0
      !ptr

      ptr = PETSC_NULLPTR
      ptr = NULL
      ptr = 0

and for completeness’ sake:

      PETSC_NULLPTR == NULL

## Example Usage

      // may be used in place of '\0' or other such terminators in the definition of char arrays
      const char *const MyEnumTypes[] = {
        "foo",
        "bar",
        PETSC_NULLPTR
      };

      // may be used to nullify objects
      PetscObject obj = PETSC_NULLPTR;

      // may be used in any function expecting NULL
      PetscInfo(PETSC_NULLPTR,"Lorem Ipsum Dolor");

## Developer Notes

`PETSC_NULLPTR` must be used in place of `NULL` in all C++ source files. Using `NULL` in source files compiled with a C++ compiler may lead to unexpected side-effects in function overload resolution and/or compiler warnings.

## See Also

`PETSC_CONSTEXPR_14`, `PETSC_NODISCARD`

## Level

beginner

## Location

include/petscmacros.h

## Examples

src/snes/tutorials/ex28.c

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